Role of First Police
Responder Towards Crime Scene
This module has been designed to provide police officers with information pertinent to their responsibilities as the “First Police Responder” to the criminal offense crime scenes. The course is built on information gathered through years of actual police experience, as well as information pertaining to the scientific forensic examination of physical evidence. The need for this training is derived from statistical data and on-site assessments of police organization’s world wide. That information indicates valuable physical evidence is often being contaminated or destroyed, and crucial witness information overlooked, due to a lack of training and proper organizational protocols. It is the goal of this training course to instill a new appreciation and understanding of the valuable role every patrol officer plays in the criminal investigative process.
For more than a century, countries throughout the world have relied on the services of the police organizations to solve crimes. Much has been said and written about the criminal investigators, and almost always complete credit for solving a crime is given to the investigator in charge. Rarely, if ever, is any credit given to the first police officer to the to reach the scene, yes it is that “First Police Responder” who acts as the initial care taker and decision maker for potentially crucial evidence. It is the decisions of the first officer on the scene that bears strong influence on the eventual outcome of the crime scene and subsequent follow-up investigations. Without the correct actions of the “First Police Responder”, many cases would go unsolved, regardless of the abilities of the criminal investigator assigned to the case.
The course contains a complete description and explanation of the various forms of physical evidence that a “First Police Responder” can expect to encountered at crime scenes. Participants will be instructed on how to recognize and protect such physical evidence. Participants will also receive instruction on the value and strengths of the various forms physical evidence once collected and subjected to forensic examination.
completion of this module, it is expected that trainees will be able to fully understand their goals and responsibilities as a “First Police Responder and will also acquaint themselves with new knowledge and appreciation of the important role physical evidence plays in the criminal investigative process.
The two most basic functions of the police work are:
The protection of life and property
The maintenance of the peace.
When these fundamental functions fail, a third basic task takes place in the form of Criminal investigation, to bring the criminal to justice through analysis of information, consisting of persons and things. To achieve the objectives, the investigator desires a crime scene rich in physical evidence and witnesses. The “First Police Responder” plays a key role in the initiation of the criminal investigative process. Many investigations either succeed or fail in the first few minutes after a crime takes place simply through the wise actions of the first police officer to reach the scene. The criminal investigator serves an important role in the modern police department by performing these critical tasks. In order for the criminal investigator to have the best possible chance of completing a successful investigation he or she must first have a well protected crime scene.
I. Criminal Investigation
A. Definition of a Crime
A crime is an act or omission forbidden by a law and punishable by a fine, imprisonment, a combination of both, or even death.
B. Definition of a Criminal investigation
A criminal investigation is the lawful, objective, logical, search for people and things useful in reconstruction the circumstances surrounding the commission of a crime to determine the truth relating to what happened and who is responsible.
C. The Goal of a Criminal Investigation
The goal of a criminal investigation is to determine the truth of the matter, as far as it can be found, in a post facto inquiry (after the fact), so that a perpetrator can be brought to justice or an innocent party cleared.
1. A good investigation has been conducted when all the investigative leads have followed to their logical conclusion. Sometimes, there simply might not be enough evidence to support an arrest. An arrest does not have to be effected in order to have a competent investigation.
2. The opposite can also be true. Just because an arrest is made in a case. This does not always mean that a good criminal investigation has been conducted.
3. If the investigator does not develop all leads to logical conclusions, the defense will most assuredly point this out at trial.
4. The justification for
making an arrest usually requires a lesser degree of proof than the deliberate,
meticulous process required to convict and to commit a suspect to prison. In the
(What is the standard in
D. Requirements of a Criminal Investigation
During the course of a criminal investigation, the following questions should be answered:
1. Did a violation of criminal law occur?
2. Where and when (time and date) did the crime occur?
3. How is the victim of the crime committed?
4. Who is the victim of the crime
5. Were there witnesses to the crime?
6. What evidence is connected to the crime?
7. What indicators are there to support a finding of guilt on the part of the suspects(s)?
8. Who are the perpetrators of this crime?
E. Information vs. Evidence
Investigations involve the task of obtaining and evaluating information. The investigative process must be thought of in terms of obtaining information, invested of obtaining evidence. Information is essential in order to understand the relationship between the crime and the items of evidence.
F. Sources of information
There are two sources of information: people and things.
1. Information from People
Information is derived from people and may not always be admissible in a court of law. Information consisting of rumors, tips, and hearsay can often place investigators on the right track to solve a crime. The collection of this information requires the unique skill and ability to elicit facts that can be used to help uncover the truth, whether it comes from the victim, an eyewitness, or a suspect in the crime. Each source must be dealt with a unique and skillful manner in order to obtain the information desired. A good investigator must be well-versed in conversational skills and may not be readily forthcoming.
2. Information from Things
Physical evidence, that being any type of evidence having an objective existence, that dimension, size or shape, can often provide invaluable information to the investigator. However, this information cannot be used if the investigator does not understanding and recognize the strict rules for collecting, preserving and presenting this evidence once it is discovered. Physical evidence consists of inanimate objects that cannot lie or flee. The investigator must develop a keen sense of detail when concerning potential items of evidence. Frequently, key items of evidence may be microscopic in size, but monumental in helping prove a crime has been committed. For example, hair, fibers, or minute specimens of blood may provide an item of physical evidence that helps convict a criminal in the absence of eyewitness identification.
Familiarity with forensic science is essential to becoming successful investigators. Physical evidence cannot generally speak for itself. It needs someone to identify it, interpret it, and then present it for final evaluation by a court
3. Relative Weight of Information
Courts throughout the world have consistently given higher relative evidentiary value to information obtained from persons. The reason for this is firmly established in the fact that things cannot lie and are not effected by emotion or motive. Direct testimony from persons may be subject to any of these defects. Therefore, courts have always given more weight to physical evidence when trying a case.
4. Balancing the Scale
Verbal testimony must strike a balance with physical evidence before a criminal investigation is considered complete. A case heavily weighted in one direction or the other exclusively can result in a questionable outcome
5. Unanswered Questions
After obtaining all of the information and evidence related to the case, the investigator may still not able to answer all of the questions surrounding the crime. Quite frequently, cases are closed and forwarded to the prosecutor for trial with some unanswered questions. This is not always the fault of the investigator, but many times a reflection of the various individuals involved in the case, as well as the evidence discovered. Some of the reasons that all of the investigator’s questions may not be answered include:
a. Incomplete information or confusion on the part of the victim due to trauma or stress related to the offense.
b. Missing or destroyed evidence due to purposeful or accidental actions on the part of the victim and/or suspect. The victim of a rape may feel the need to wash before calling the police, thereby innocently destroying valuable evidence. A suspect may permanently dispose of a murder weapon, thereby eliminating it a key piece of evidence.
c. The suspect may confess to the crime, but leave out pieces of key information in an attempt to downplay his/her premeditation or to lessen the role they played in the crime, particularly if there are accomplices.
d. Eyewitness to the crime may provide inaccurate information due to personal bias, confusion or fear of retribution by the suspect(s).
e. Eyewitnesses to the crime may have departed the area before the police and may never come forward to offer their information.
II. The evolution of a Criminal complaint
Once a crime has been committed, the crime may or may not come to the attention of the police. In order for the police to conduct an investigation, they must be aware that a crime has occurred. A crime may come to the attention of the police in a number of ways. The primary manner is generally through someone reporting the crime directly to the police.
The reporting of Crime(s) to the police can be accomplished in a variety of ways.
1. By a Victim
2. The crime may be reported by the victim, such as robbery or assault. By bringing the crime to the attention of the police, the victim has initiated the first step in the investigation – notifying the police.
3. By an Eyewitness
4. An eyewitness or other person may have knowledge of a crime that has been committed and notifies the police, or someone else, who brings it to the attention of the authorities.
5. By an Accomplice
6. An accomplice in a crime may confess his/her involvement in the crime. For example, a person who is arrested in a minor offense may tell the police information about a crime that has been committed by someone else.
7. by an Anonymous tip
8. An anonymous may be provided by an unknown person in hopes of having police arrest the perpetrator, or simply enact revenge on an enemy or competitor, such as rival drug dealer.
9. By an Informant
10. An informant, (someone who secretly provides information to the police about a crime), may provide information relating to a crime in order to collect reward money.
Discovery of a Crime by the Police
1. By plain View.
2. Circumstances where the police actually happen upon a crime in progress come upon it by chance shortly after the crime has occurred.
3. The police, in the course of an investigation, may uncover evidence of another crime. An example might be where the police are at home investigating a complaint of domestic assault, and happen to notice illegal drugs or stolen property in the home.
C. The Preliminary Investigation
Once the crime is discovered, a preliminary investigation is initiated. This investigation is usually conducted by the police officer in the field (The First Police Responder) who first responds to the call for service, or discovers a crime in progress. The preliminary investigation helps establish that a crime has been committed, attempts to identify the perpetrators(s), and protects any crime scene until qualified evidence technicians and/or the preliminary investigator arrives. In some cases, if an arrest cannot be made immediately, the preliminary investigation involves an in-depth effort on the part of the first responding officer prior to the case being passed on to an investigator who picks up the investigation and attempts to solve the crime.
D. The Follow-Up Investigation
Follow-up investigation is conducted when the preliminary investigation does not result in the immediate apprehension of a criminal. A follow-up investigation is usually handled by a criminal investigator, who preferably has the following:
1. Sufficient time available to conduct a thorough investigation of the crime.
2. Detailed experience in investigating the specific crime, such as robbery, homicide, or sex crimes, etc.
3. A particular familiarity with the type of crime committed and the specialized equipment or particular MO used such as computer crimes involving unauthorized access to financial or personal electronic accounts.
The police are assigned the broad responsibility of the preventing crime. When crimes do occur, the police initiate criminal investigations to identify and bring the offender justice. Criminal investigations involve a wide range of activities, starting with the initial notification that a crime has been committed. Each criminal case provides the investigator with anew challenge, and each case must be addressed in its own unique manner. (A typical criminal persons and things). This information must be balanced in its relation to the case to ensure that an accurate picture is developed of the facts surrounding the crime.
The first police officer to respond to the scene of an alleged criminal offense represents the first step in a proven investigative process. As with any successful formula, the ingredients must be correct. The First Police Responder is the key ingredient in the formula that must be followed to conduct “a successful criminal investigation.”
The Well Prepared First Police Responder
The purpose of this chapter is to provide the participant with the understanding that preparation, in the categories of equipment and knowledge, is an essential requirement for the success of the First Police Responder.
In order to be successful First Police Responder, the participants must first prepare to meet the challenge. In this chapter, participants will learn the value of advanced reference information, the correct use of the police notebook, and proper control of police information.
I. Preparation – The key to Success
Before you receive the call to respond, you must be prepared with the police knowledge, resource information, equipment, and ingenuity required to get the job done. Ask any police commander who his best officer in the street is and he or she will give you the name of someone who possesses those attributes.
A. You must know the geographic boundaries of your total your jurisdiction and those of your particular assigned patrol area
B. You must know any and all limitations to police authority within your jurisdiction
1. Foreign Embassy involvement – ambassadors, official family members, Embassy staff, foreign domestic staff and other embassy owned or leased properties,
a. Do you have the power of arrest, and search and seizure, on the grounds of foreign embassies that are located within your jurisdiction?
b. Do other foreign embassy properties other then the official embassy building enjoy the same privileges are main embassy?
c. Does diplomatic immunity cover only ambassadors and their immediate family members, or does it also apply to other members of the embassy staff, and if so what members?
d. Are motor vehicles owned by foreign governments given the same immunity status as are embassy buildings?
e. Do you have the right to detain members of the foreign diplomatic community for any purpose?
f. Do you have the right to detain members of the foreign diplomatic community for any purpose?
g. Do you know your agency’s protocol when members of the diplomatic community are involved in a crime as either victim or suspected of being involved in a crime as either victim or suspect?
h. In the event of such an occurrence, who are you required to notify and when?
2. Military installations are many times considered to be apart and separate from civilian population and property. For that reason the civilian police departments may not have absolute authority over domestic military personnel or power to investigate the within the boundaries of military installations?
a. Can you conduct police business on a domestic military installation without first gaining the approval of the Provost Marshall or some other appropriate military official?
b. Do you have the power to arrest on a arrest on a member of the military either on or off a military reservation.
c. In the event you are called to render police services on what you know to be military property, who should you notify?
d. Are foreign military personnel and properties, located within your jurisdictional boundaries exempted from local police jurisdictional?
e. In the event you are required to arrest a member of foreign military, what are your agency’s protocols?
3. Foreign Marine Vessels, Aircraft often enjoys some form of immunity when at port or on the ground in countries other than their own.
a. What is you authority and responsibility, if any, in law enforcement matters involving foreign transports and carriers?
b. Are there other law enforcement authorities within your country that are assigned to handle enforcement over foreign aircraft and marine vessels?
c. If faced with such a situation, who are you required to notify?
4. Domestic Vessels, Aircraft and Rail
a. What is your law enforcement authority and responsibility in law enforcement matters involving domestic transports and carries?
b. Are there other law enforcement authorities in your country that country that are assigned to handle enforcement over domestic aircraft and marine vessels?
c. If faced with such a situation, who are you required to notify?
C. You should have a complete knowledge of all available emergency assistance and all current corresponding telephone numbers.
1. Medical Emergency Assistance and Fire Suppression
a. If medical assistance is required at location, and radio transmission is somehow compromised, you should know the phone number of your nearest fire and ambulance emergency service.
2. Specialized Police Services
Crime Scene Evidence Unit, FIA, CID, Crime Branch and Investigation Units etc.
3. Public Utilities
a. Electric, Gas, Water and Sewer Services
D. You should know your police organizational notification procedures. For reasons of continuity and chain of command every police organization must have a prescribed order in which ranking police officials are to be notified of current police activities within their command area. That process of notification starts with the first police officer on the scene. A well prepared First Police Responder will:
1. Notify the correct investigative unit when needed
2. Notify the correct police official
3. If both an investigator and the evidence unit are needed, he will notify both or to both to respond and not wait until higher authority arrives to make that decision. Remember – The longer a scene sits prior to processing for physical evidence, he greater the possibility for contamination
4. Never call friends, other non-essential personnel to the scene.
Note: Excess police personnel/sightseer are the number one cause for crime scene contamination
5. Never notify the press or a private photographer.
E. You must know basic first aid, and life saving procedures such as:
1. Know the signs of life and how to check for them
2. Know how to properly administer CPR
3. Know how to treat for shock and control bleeding
4. Do you have the basic supplies to provide basic first aid?
F. Carry the right supplies and equipment and to get the job done:
1. A police notebook with enough blank pages for recording an average criminal investigation
2. Tape a pencil to your flashlight just in case it rains. Ballpoint pens don’t work on wet paper, but pencils do
3. Carry a flashlight with fresh batteries and an extra bulb
4. Carry a pocket knife
5. If portable police radios are available, keep one with you at all times
6. Maintain an small supply of protective supplies with you to avoid personnel contamination from air bourns pathogens such as Hepatitis B and HIV. Although such biological protective gear is not called for on every assignment, it is recommended that the following disposable protective supplies be kept on hand in the event circumstances dictate a need for such protective equipment:
a. Latex gloves
b. Particle mask
c. Shoe covers
d. Jumpsuit or plastic apron.
7. Crime Scene ribbons if available, surveyors ribbon, or rope
8. Dress appropriate according to the weather forecast for your area II.
Your police notebook – A vital tool for all police officers
A. Your police notebook should have written on its cover:
1. Your name and assignment
2. The date you started and finished that particular notebook. (Notebooks should be stored in a safe place in order by date)
B. Your police Notebook contain:
1. A list of all important telephone numbers pertinent to the successful completing of your duties as a “First Police Responder.”
a. If you are able to type out a master list in such a fashion that it will fit inside the back cover of you notebook, then it can be reproduced on a copy machine for use in future notebooks.
2. Only information pertaining to your individual police assignments.
3. Your notebook should not contain:
a. Any personnel information pertaining to yourself such as home address, phone, family names, etc.
b. No other personnel entries such as grocery lists, clothing sizes for birthday gifts, girlfriends phone numbers, dates for the family gatherings or up-coming events etc.
4. The information contained in your notebook should be brief but complete enough to allow for follow-up
a. Start each days entries with the date and time
b. If making notes of a conversation, attempt to get an address and telephone number from that person so the investigator can make a follow-up contact
c. Ask the kind of questions you would want answered if you were the investigator assigned to complete the investigation
d. When speaking with a potential witness never fail to ask questions like: who was with you at the time? Who else did you see outside at the time you witnessed the event?
e. Never settle for a first name only, always attempt to get some other information on the person. If the last name is unknown to the witness, then try for something else that will help the investigator follow-up on your information i.e. the persons work place residence, or where does he attend school. (GET SOMETHING)
f. Always ask the question: “Who else lives at your address and were they home at the time of the offense?” That question opens the door for the potential of more names for the investigator to explore as possible witnesses.
g. Remember that everything you write in your notebook is a Public Record and could be used by someone other than yourself, so get correct and write nothing that involves your personnel opinion. III. The value and Power of Information – The Need to Know
A. Information pertaining to facts about the investigation such as motive, victim’ s name, number of victims, number of shots fired, the existence of eyewitnesses, caliber of weapon, are all commonly asked questions. The First police Responder must be aware that to reveal any information surrounding the facts of the investigation would most likely severely jeopardized the successful outcome of the investigation. The mere mention of eyewitness’ names could lead to their death or seriously injury. It should never be forgotten that members of the news media, civilian personnel, court personnel, and yes, even fellow police officers could represent potential leaks of information. Such leaks of information, regardless of whether they are intentional released or through innocent conversation, could ruin an investigation and any future prosecution.
B. The control of information is vital, and it starts with the First Police Responder. Information pertaining to an active investigation should be controlled by the primary investigator. Any and all press releases should be handled through existing Police Public Information Officers, or the appropriate means as dictated by your police organization. All information unique to a particular investigation must stay confidential.
The information covered in this lesson represents basic, fundamental knowledge that the First Police Responder must have in order to correctly take charge of a crime scene. It should be understood that the order of events can will change from one crime scene to another; however, it is always the responsibility of the officer to see that the crime scene is properly managed until the arrival of the primary investigator. In this lesson we have learned that the First Police Responder represents the first vital step in the investigation of a criminal offense. Each participant should now have an enhanced appreciation of his importance and value in the overall criminal investigative process.
Goals and Responsibilities
Of the First Police Responder
The primary goal of any First Police Responder is to preserve life, arrest offenders, and prevent contamination of potential physical evidence by various categories of responsibility required of a First Police Responder for the accomplishment of assigned responsibilities.
I. The notification to respond for police service.
A. From whom can the respond for police service.
1. The police radio dispatch
2. a superior police officer, in person, radio or telephone
3. a private citizen, in person or telephone
a. In the event a private citizen notifies you that there is a need for police service within you assigned area, immediate notification of the police dispatcher should be made. By alerting the dispatcher or at a minimum some other police unit, as to your intended destination, you will be assured of timely assistance if needed.
b. In the event of an emergency, no police officer, regardless rank or assignment, should place himself in the situation of being on official police business without his location being known to other police officers. This is of paramount importance to officer safety.
c. Record any and all information provided to you at the time of the initial notification to respond regardless of who the information came from. Remember, the moment you are given an assignment it becomes your responsibility to take charge of that assignment.
1. Time of notification
2. Date of notification
3. Location/address of assignment
4. Type of assignment
5. Name, address and telephone number of reporting or persons
6. all details of offense available from the reporting person or persons
7. Always ask if the suspect is armed (always assume he is armed)
d.Respond to the location in a timely fashion and obey any and all departmental orders regarding emergency respond procedures.
1.Take Charge-Many police officers fail to recognize and understand the importance of their role as a First Police Responder.” It is important for all officers to realize that once given an assignment to respond to the scene of an alleged criminal offense, they are in charge from that very moment until relieved by higher authority. Anything and everything that happens on that scene until the arrival of higher authority rests on the shoulders of the first officer.
2. Request information of the person making notification to you. If the call involves a crime of violence, you would want to know the answers to questions pertaining to officer safety: Is the suspect still on the scene? Is he armed? The suspect name and/or physical description. What about the victim? Present location, Condition, Name of medical facility if already removed from the scene, etc.
3. If the information available prior to your arrival at the scene indicates that additional assistance will be needed to accomplish your goals and responsibilities, then make that request while en route. An example of such a request could involve the request for another police unit to respond to the medical facility where the victim was transported. That unit would be responsible for obtaining information about the victim’s injuries, suspect description, as well as safeguarding potential evidence from being destroyed by well meaning hospital staff. Doctors and nurses are only interested in preserving life, not investigating crime
4. If the assignment is reported to involve potential bodily injury or sexual assault, emergency response equipment, ie. red lights and siren, are an appropriate choice. By loudly announcing your intended arrival, the suspect might discontinue the assault, thus preventing further injury to the victim. What is your police organization’s policy?
5. If the reported assignment involves an alleged property crime, where bodily injury is not an anticipated element of the offense, approaching in a silent (stealth) mode is more appropriate. In conducting such a response method, the suspect might still be on the scene at the scene at the time your arrival, thus allowing an opportunity to conduct an on-scene arrest.
D. Arrival at the alleged crime scene location
1. Never drive your police vehicle to a location directly adjacent to the reported location of offense. A wise “First Police Responder” will, whenever possible, park a short distance from the alleged scene for the following reasons:
a. Officer safety-making the initial assessment, identify possible hazards
b. Prevents possible contamination or destruction of physical evidence
c. Start the process of taking on-scene notes time of arrival weather conditions Lighting conditions
d. Observe for person and/or vehicles leaving the crime scene area Make notes on those observations – physical description, tag numbers etc.
Practical Exercise: With the use of your police notebook, record and description of the person pointed out to you by your instructor. When making notes on the physical description of a suspect or potentia Example: Black male, 6 foot, medium build, red baseball hat, black trousers, white tennis shoes.
E. While continuing correct officer safety practices, locate the reporting person ascertain the following information: It should be noted that circumstances at the scene may prevent the officer from following the order in which events are outlined in the text. In many cases, fast action to preserve life, arrest offenders, protect property, and prevent the contamination of potential physical evidence, will take priority and thus rearrange the chronological order of events. The responsibility of gathering information still falls on the shoulders of the “First Police Responder.”
1. Verify the reporting person’s name, home address, work address, and telephone numbers to include cell and pager numbers.
2. Ask who else lives at that person’s address, and if they are there now. By asking this question you open the door to other potential witnesses
3. Quickly ask the who, what, when, where, why and how questions pertaining to the alleged offense. 4. Request that the reporting person remain at your home until the investigator arrives.
F. While continuing correct officer safety practices, locate the victim and:
1. Render first aid if required and call for medical assistance.
2. Ask the who, what, where, when, how, and why
questions of victim (if possible) Note: In the event the victim is critically injured
and the possibility of death is present,
the officer should take a Dying Declaration statement from the victim. The following procedure details the
legal requirements of the
3. Broadcast a lookout with a top-to-bottom description of the suspect
4. Determine the basic crime scene area and establish preliminary boundaries to protect that crime scene.
5. With the exception of injured persons who are unable to be moved, remove all persons from within your established crime scene perimeter.
6. Remove all pets and domestic animals that are not caged and capable of destroying or otherwise contaminating the crime scene.
7. Identify and separate obvious and potential witnesses.
8. take good notes of only what you see and hear, not what you think. The police notebook does not have room for speculation. Do not create ammunition for the defense
9. Maintain control of crime scene area; expand boundaries if required.
10. Remain on the scene and maintain control until the arrival of the primary investigator in charge
11. Turn over all information to the primary investigator in charge
12. Continue on scene assistance until relieved
G. In the event you determine the victim has already been removed from the scene, steps must be taken to preserve any and all physical evidence that left with the victim.
1. The First Police Responder should call for assistance and request that another police respond to the medical facility and interview the victim as well as take measures to prevent any potential physical/ trace evidence.
2. The victim will also be able to give information needed to properly establish the correct crime scene boundaries and a description of the suspect.
3. A description of the victim’s injuries is also extremely helpful. Information such as the nature and extent of stab or gunshot wounds, the number of projectile exit wounds, the distribution and description of blood on the victim, and other particulars can and will be of great assistance in the actual crime scene search. H. In the event an apprehension of the suspect is made at the scene, or within 24 hours of the actual criminal event, the clothing the suspect is wearing, and the actual body of the suspect, must be treated as locations for the recovery of potential trace/physical evidence. Remember that any time a crime is committed, if the crime involves an actual on-scene victim, the suspect and victim becomes part of the crime scene and therefore could yield trace evidence such as hairs and fibers, physiological fluids, and even latent prints. III. What constitutes a crime scene? How does the First Police Responder identify the actual crime scene perimeters? How is that area protected?
A. Simply put, a crime scene is that physical area within which all actions taken by the perpetrator and the victim took place during the entire as criminal event. Examples of indicators include:
1. Bullet holes, projectiles and shell casings resulting from shots expended during the criminal offense in question;
2. Blood trials leading to and from the offense location;
3. Footwear and tread wear impressions in and around the crime scene.
4. Obvious areas of disruption such as over-turned furniture and broken items;
5. Items of clothing and implements of crime; and
6. Statements of victim (s) and or witnesses pertaining to where the crime occurred.
B. The determinations as to what constitutes the actual crime scene is based on a combination of four sources. The First Police Responder must make his initial assessment as soon as possible after arrival at the scene. This quick action is essential to ensure the proper protection of potential physical evidence:
1. The information received from the victim, (if available);
2. Information obtained from potential witnesses;
3. Personal observations made at the scene indicating involved area; and
4. Good common sense and police experience.
C. Who and What can contaminate a crime scene and/or destroy potential physical evidence at a crime scene:
1. The Suspect;
2. The victim;
3. Other family members, friends, pets and animals;
4. Emergency Medical and Fire personnel;
5. Inquisitive Police Officer;
6. High Ranking Police and Government Officials;
7. Onlookers, souvenir collectors and thieves;
8. News Media Personnel;
9. The Weather; Personnel;
D. How can one person establish a crime scene perimeter and the maintain its security in order to protect potential physical evidence.
1. Use what ever means available to establish a clear boundary line around the suspect crime scene area.
2. Call for assistance if needed, civilian assistance (if not life threatening) until other police assistance arrives.
3. Block off entire streets with vehicles (civilian if required)
4. Use any large objects, clothes lines, garden hoses, anything available as long as those objects did not originate from within the known crime scene area.
5. NEVER use items from within the known crime scene area to assist in securing a crime scene perimeter because in doing so you are, at a minimum, altering the crime scene and quite possibly destroying potential physical evidence
E. The universal rule for the establishment of a good crime scene perimeter is:
1. When in doubt of the actual crime scene boundaries go bigger than actually needed.
2. The philosophy behind this rule is found in the saying “It is easier to make a crime scene smaller than it is to make it bigger.”
3. Don’t be fooled – It is possible for a crime scene to appear to be completely undisturbed, thus giving the appearance of being uninvolved in the actual event. That same area has the potential of yielding valuable items of physical evidence that can help solve a case.
IV. Who is and who is not allowed to enter the crime scene area prior to the arrival of the primary investigator and evidence technician
A. In A Perfect World – Nobody until the primary arrives
B. In the Real World – there are reasons why certain persons should be allowed to enter a crime scene prior to the arrival of the primary investigator. The following persons should be allowed to enter if circumstances dictate:
1. Medical Emergency Personnel
a. Whenever medical teams are required to enter a crime scene it should only be for the medical treatment of persons who otherwise cannot be treated at a location outside of the established crime scene perimeters
b. The First Police Responder must always oversee the complete actions of the medical team members. They are be advised of the following prohibitions: Restrict movement to an absolute minimum; Do not touch or move anything without prior approval of the Officer; Make no attempt to clean-up. All medical debris and other indicators of their presence on the scene are to be left as is; and At all times the medical staff is to be guided by the Officer. Always make note/rough sketch in your notebook of the position of the victim’s body prior to movement by emergency medical personnel.
c. Firefighters If while in the course of fighting an actual fire, an arson or some other criminal offense is suspected, fire suppression is to be held to an absolute minimum. Normal “overhaul” procedures are to be avoided if possible. If fire personnel are required to enter an interior crime scene to conduct safety inspection team and deliver the same admonishment as was presented for emergency medical personnel.
d. The following personnel should not enter a crime scene prior to the arrival of the primary investigator. Other police officers All civilian personnel are prohibited from being within the scene perimeters. This includes the victim, family members, other occupants, witnesses, business owners, the media, clergy, and government officials. Judicial judges or other Competent Legal Authority It is understood that in Lebanon Judicial judges respond to crime scenes and take custody of items of physical evidence from either the evidence technician or the primary investigator. There is, however, no reason why a judge should enter a crime scene prior to processing for physical evidence. Police Officials – All higher ranking police and government officials requesting entry should be advised that the potential for contamination and/or the destruction of potential physical evidence is extremely high and that in accordance with your police training you will have to record the name of each person who enters without your approval. It is understood that such an admonishment of a higher ranking police or government officials can come with potential consequence. It is, however, the responsibility of the First Police Responder to state his request in such a manner as to be both respectful and convincing. Such professionalism on the part of the Officer, when tempered with the greatest of respect for rank, is difficult to disregard.
IV. Suggested solution to “Sightseeing” by Police Officials
A. The Police Command Post - All police Officials can play their most important role in the investigative process by using their rank and power to get things done. The First Police Responder should recognize this, and request the visiting official to create a Command Post. Having received this request, the Officials now has a purpose for being there, and the officers has gained powerful assistance in maintaining the integrity of the crime scene. The Official can call for additional manpower to aid in protecting the crime scene perimeter and to help in locating potential witnesses.
VI. Duties of the Secondary Officers Arriving at the Crime Scene
A. With few exceptions, every crime scene will have additional police officers arrive at the scene a short time after the initial call goes out. Some of those officers come to help and others offer no more help than the average spectator. The first responder officer should request the assistance of any officer available in order to accomplish his mission. Additional officers could be requested to:
1. Clear the Crowd The crime scene and adjoining area should immediately be cleared of spectators and non-essential personnel to prevent contamination of the crime scene. Such a procedure, although necessary, will often result in the dismissal of potential witnesses.
2. Do not Send Witnesses Away Care must be exercised so as not to send potential witnesses away. Police officers typically tell people near the scene that everything is under control and everyone should go home. Unfortunately, a valuable witness may be sent away without first obtaining pertinent information. Police officers should be instructed to request the assistance of all spectators by announcing that: The police are requesting the assistance of the public ; Anyone who thinks they might have seen something about this event should remain at the scene and make there presence known to the police; and, Anyone would thinks they might have seen something about this event should also remain and likewise make their presence known to the police. To accommodate persons who wish not to be identified or who are reluctant to come forward at that time, an announcement giving the investigator’s name and the officer’s name should also be made along with a request to please contact the police if additional information is available.
3. Help Secure the Immediate Crime Scene The crime scene should remain sealed until the investigator arrives. As secondary officers arrives at the scene, they should help ensure that the crime scene is properly secured.
4. Help Establish Perimeters These additional police officers can be used to better define and limits of the crime scene by establishing clearly defined perimeters.
a. Inner Perimeter – An area that includes all area where evidence of the crime is likely to be found.
b. Outer Perimeter An area immediately adjacent to the inner perimeter of the crime scene, which is unlikely to be directly involved in the crime. This is the area where the media and general public are allowed to gather. Curiosity is natural and it is almost impossible to exclude the public from the area of a high profile crime. This is also the area in which a Command Post should be established to coordinate the efforts of the police and other agencies.
5. Use Police Notebooks Secondary police officers should be requested to record the tag numbers, and brief description, of all motor vehicles parked in the area of the crime scene. This information can assist the primary investigator with potential witnesses information. Secondary officers should also be requested to record any observations they make which they think will aide in the overall investigation. Such observations could include unusual behavior, emotional distress, physical injury, or anything else that would lead the officer to believe a persons actions or appearance to be suspicious.
Practical Exercise # 1 Participants will be divided into small groups and instructed to respond to mock crime scene locations. At each location participants will be required to gather information from various potential witnesses. In additional, each mock crime scene location will present situations requiring decisive actions on the part of the participants. Participants will be expected to record complete and accurate information in their police notebooks, as well as make correct decisions based on the training information presented during the proceeding three chapters.
In the lesson, we have looked at the general sequence of events from the initial call to respond, to the point where the crime scene is turned over to the primary investigators in charge. We addressed the need for the first police responder to recognize the potential outside influences that can alter a crime scene. We learned that long before the investigators arrives at the crime scene these outside influences can have a tremendous impact on determining if evidence at the crime scene is properly preserved, or needlessly contaminated. We have also learned that although circumstances and the sequences of events can change the order in which the duties of the first police responder are carried out, it is still essential that all tasks are methodically accomplished.
Introduction to Physical Evidence
It is understood that as uniform patrol officers the participants are not responsible for the recovery of physical evidence. It is however extremely important that all police officers have a thorough understanding of the general categories of physical evidence, how to recognize such evidence, and the potential value such evidence can bring to bring to a criminal investigation.
The value of physical evidence is determined by how useful it is verifying that a crime has been committed, identifying the person(s) who did it, and exonerating all other persons who may be under suspicion.
Physical evidence has great potential in all these regards. To realize its full potential, the police crime laboratory examiner, and the prosecutors must work together to present a set of facts that make it unreasonable to believe any conclusion other than the one the facts support-even though any one of the facts, taken alone, may be open to reasonable doubt.
In order to accomplish this important task, there are certain qualities of evidence that must be obtained, and some minimum qualities collected before the crime laboratory can be of any assistance. It is no exaggeration to say that, in the majority of cases, the First Police Responders who identify and protect a crime scene play a critical role in determining whether the scientific expertise of the laboratory will be brought to bear in a case.
Definition of Evidence
A. Evidence is defined as what is legally submitted to a competent tribunal as a means of ascertaining the truth of any alleged matter of fact under investigation before it.
1. Evidence is anything that a suspect leaves at a crime scene or takes from the scene, or which may be otherwise connected with the crime.
2. Evidence can be anything that tends to disprove an issue in question. It is the means by which any alleged matter of fact is proved or disproved. It includes all matters, except comment or argument, legally submitted to a court to enable it to decide a question before it.
II. Types of Evidence
A. Evidence can be divided into two types: testimonial evidence and physical evidence.
1. Testimonial Evidence
a. Testimonial evidence is provided in the form of a statement or testimony provided under oath. Testimonial evidence is usually subject to questioning and additional clarification.
2. Physical Evidence a. physical evidence is any type of evidence having an objective existence, that is, any dimension, size, or shape. Physical evidence can take almost any form and can be as minute as a microscopic fiber in a rape case, the odor of an flammable liquid at the scene of a fire, or as large as an automobile involved in a hit and run accident. For the purpose of this lesson, we will be connected on physical evidence.
III. The Purpose of Physical Evidence
A. To Prove That a Crime Has Been Committed, or Establish Key Elements of the Crime
1. Example: Investigators might collect pieces of carpeting at the scene of a house fire and have it tested for the presence of flammable liquids. If such a substances was present inside the home, such physical evidence could be used to prove that the fire was deliberated set. This would establish one of the elements of arson.
B. To link a Suspect to the Victim or the Crime Scene
1. Example: The suspect in a burglary might be apprehended shortly after the crime and subjected to the seizure of his clothing. A laboratory examination of the clothing could reveal hairs identical to those of the victim, pets in the home, or even carpet fibers originating from the crime scene.
C. To Establish the Identity of Persons Associated with a Crime
1. Example: A serial rape suspect may be subjected to DNA testing and be positively linked to some or all of the rapes.
D. To Exonerate the Innocent
1. Example: A sore clerk claimed that she was sexually assaulted by her store manager after closing. She tells the authorities that she was drugged, passed out and then awoke to discover that she had been sexually abused. When the laboratory analyzed her urine, the results did not indicate the presence of any type of drugs. When later confronted, she confessed that she had made up the story to get back at her boss for his mean behavior towards her.
E. To Corroborate Victim’s Testimony
1. Example: A suspect in a serious assault case was positively identified by the victim as the perpetrator. During the attack, the victim was severely beaten and forced to kiss the suspect’s feet and beg for mercy. When the suspect was arrested, minute traces of the victim’s blood were later identified on his shoes, thereby corroborating his testimony.
F. To Induce a Suspect to Make Admissions, or Even Confess 1. Example: A suspect in a murder was told that his particular brand of cigarette had been discovered at the scene of the murder, along with his saliva, identify through DNA testing. The suspect had steadfastly denied ever being at the victim’s home. Faced with this convincing physical evidence, the suspect immediately changed his alibi and admitted that he had been at the suspect’s home prior to the murder.
G. Absence Of Evidence Can Help Provide Proof
1. Example: A homeowner submits a large claim to the insurance company for a burglary. In the claim, the homeowner asks for reimbursement for various jewels, electronics, and other high priced belongings. When confronted with the obvious lack of forced entry and no receipts, the homeowner confesses to the fraudulent scheme.
H. Physical evidence Can Be More Reliable than EyewitnessTestimony
1. Physical evidence speaks for itself. It dosen’t forget, or become flustered on the stand. Eyewitnesses often see things differently and seldom do two witnesses provide identical observations. Frequently, witnesses will fill in gaps in their testimony when they didn’t really see everything. Additionally, with time and under cross-examination, witnesses sometimes freeze and fail to provide the testimony they previously offered. This never happens with physical evidence.
IV. General Rules of Evidence
A. Investigator Conduct As a general rule in almost every country, criminal prosecution often depends on the proper investigative conduct of the police at the scene of the crime. It is imperative that the foundation for successful prosecution be an accurate and thorough investigation. Something more the mere collection of evidence is required to support a successful prosecution. Evidence must be obtained that will be admissible in court. Every country and every court has its own rules and expectations when it comes to evidence.
B. Basic Knowledge Basic knowledge of the rules governing admission and rejection of evidence is fundamental to sound investigative procedures. It is crucial to present a case in which the court will be presented with enough reliable information upon which to base a proper decision. The court must have ample information concerning any physical evidence collected, to include where it was discovered, how it was collected, how it was preserved, and how it relates to the case at hand.
C. Rules of Admissibility Since evidence is the source from which the judge or jury must form conclusions as to guilt or innocence of an accused person, only evidence which satisfies the various rules of admissibility and every investigator should be intimately familiar with them. The primary purpose of these rules, from an exclusionary viewpoint, as to ensure ensure a fair and impartial trial for the accused. Generally, the decision of a court cannot be upheld if based upon insufficient or incompetent evidence.
D. Chain of Custody Generally, in order for evidence to be admissible in a court of a law, strict accountability must be established to show where, when, and how an item of evidence was collected. In addition, sufficient testimony must be presented to establish the “chain of custody.” The chain of custody of an item of evidence shows its entire history, starting with its initial discovery, collection, packaging, transportation, examination, storage, and presentation in court. In other words, the chain of custody of an item is a detailed history of everything that took place concerning a particular piece of evidence. The chain of custody will accurately reflect the date and time every person ever touched the evidence, or moved it from the point of its discovery.
V. Basic Principles of Evidence A. The value of physical evidence is determined by how useful it is in verifying that a crime has been committed, identifying the person(s) responsible, and exonerating all other persons who may be under suspicion. In addition, physical evidence helps reconstruct the events of a crime and their sequences. Several important concepts with regard to the quality and usefulness of physical evidence in establishing identity should be considered. These concepts include:
a. Unique Characteristics Individuality is what makes one thing different from all others similar it. An individual has thousands of characteristics that are common in other people. However, every human being has many physical characteristics, such as fingerprints, ear prints, handwriting, and DNA that make him unique. If there enough common characteristics, identifiable, or if there are known unique characteristics, practical identity of a person may be established. The same may be said of identification of objects.
b. Making a Positive Identification Evidence can be positively identified as having come from a specific source or person if sufficient identifying characteristics, or sufficient microscopic or accidental markings are present. Examples of such evidence include fingerprints, handwriting, bullets, toolmarks, shoe prints, pieces of glass where the broken edges can be matched, and wood where broken/cut surfaces can be matched.
2. Class Characteristics
a. Evidence that can only be identified by placing into a particular class, regardless of the amount or thoroughness of examination, is known as evidence with only class characteristics. A definite identification as to its source can never be made, since there is a possibility of more than one source for this evidence. Example-Animal hair can be identified as having originated from a general class such as dog or cat. The hair can be described by length, width, and color, but it cannot be identified as having originated from any one particular dog. Class characteristics of an item, therefore, allow it to be screened before amore detailed comparison is made between it and another objects to determine individual characteristics that may later lead to the establishment of specific identity. Example-Multiple shell casings recovered from a crime scene will first be sorted by caliber which is a general class characteristic. Lets say you collected ten, shell casings, three of which were .38 caliber and seven of which were .45 caliber. In this scenario the general class characteristics indicate that there were possibly two different weapons present at the crime scene. It is desirable to have evidence that can be positively identified, but the value of evidence with only class characteristics should not be minimized. In cases involving evidence with class characteristics, the following are desirable:
3. A preponderance of such evidence.
a. A preponderance of class characteristics within a single item of evidence, such as paint with many layers all matching, or soil with foreign matter such as paint chips.
a. Individual Probabilities – The presence of matching fibers, hair, blood, shoe prints, or toolmarks may indicate an extremely high probability of involvement, even though none of these factors is in itself conclusive.
5. Theory of Transfer – Trace Evidence
a. When two objects comes into contact, there will frequently be a transfer of small amounts of material from one to the other. Thus, when suspects come in contact with the victim and objects at the crime scene, they frequently leave behind traces of themselves and take with them traces of any objects touched. This also applies to investigators. Materials transferred in this way are normally referred to as trace evidence. The term trace evidence is usually very loosely defined, however, it is most often applied to minute or microscopic bits of materials that are not immediately apparent to even a trained investigator.
VI. The Potential Outcome of Physical Evidence
A. Assists in the Solution of a Case
1. Develop or Identity Suspects Suspects can be developed or identified through the presence of physical evidence such as fingerprints or other exchanges of trace evidence. These provide positive proof that the suspect came in contact with a particular location.
2. Prove or Disprove an Alibi
Physical evidence can help prove or disprove suspect’s such as the presence of safe insulation on an individual’s shoes who denies being at the scene of a safe burglary.
3. Connect Suspects to a Crime
Suspects can be connected to the crime through the presence of physical evidence that proves their involvement, such as their fingerprints being discovered on the underside of a cash drawer at the scene of a robbery. These fingerprints would provide an indisputable connection of the suspect with the crime scene. In addition, the location of these fingerprints would provide an even stronger connection with the robbery, particularly when it could be proven that no one other than the store employees would routinely have access to the underside of the cash drawer.
4. Identify Property or Contraband Connected with a Crime, or Prove Involvement by the Suspect(s) As a result of a dye pack exploding during a bank robbery, the cash as well as the hands and clothing of suspect, would be readily identifiable. The unique properties of the dye would help an investigator identify the tainted cash and prove the suspect’s involvement. The suspect would have difficulty explaining how the unique dye used in the dye pack pack came in contact with his hands and clothing if he denies having had possession of the money.
5. Develop Modus Operandi or Methods of Operation (MO), or Show Similar MOs As discussed in an earlier lesson, the MOs of repeat offenders are predictable because of their tendency to commit crimes at certain times, within a specific area, using similar methods. Information about the offender can be predicted by analyzing the habits of the victim sand used to predict potential victims or targets. Physical evidence left by a suspect will often help identity the MO. For example, a robber may have the habit of browsing at convenience store while waiting for the most opportune time to commit a robbery. During this stalking period, the robber may grab a favorite brand of soda and pretend he was about to make a purchase. The soda may then be left behind once the robbery is committed. Even if useable fingerprints were never from the soda bottle, the particular brand could be identified as an accidental signature of the robber.
B. Proves an Element of the Offense
1. Shards of glass or building materials on a suspect’s clothing may prove entry. When glass or cinder blocks break, very fine particles becomes airborne and frequently land on the perpetrator without his knowledge. These minute particles can be the piece of physical evidence that places the suspect at the scene of the crime.
2. Bullets, residue at the scene of a fire, semen, blood, and toolmarks may all prove elements of certain offenses.
C. Proves the Theory of a Case
1. Footprints may show how many people were at the crime scene.
2. Automobile paint on clothing may show that a person was hit by a car instead of another cause of injury. VII. Main Sources of Physical Evidence A. The Crime Scene
1. Primary Source of Evidence
a. The crime scene is usually the focus of the preliminary investigation and also the primary source of physical evidence. It is, however, also an area with the greatest potential for the destruction or contamination of evidence. Police Officers must be diligent in avoiding accidental contamination of the crime scene not only by themselves, but by others, such as witnesses, other investigators, and environmental conditions (rain, wind, snow, etc.). 2. Contamination a. All persons coming in contact with the scene should be cautioned about crime scene contamination. Something as innocent as walking through the scene, smoking , or picking up an item for closer examination can produce contamination. Every crime scene should have a contamination sheet that lists the name, date, and time of each person’s arrival and departure from the crime scene. This sheet can also be used at a later time if the need for elimination prints should occur. 3. The Victim a. The victim of a crime is often a potential source of physical evidence, particularly in the case of sex crimes. Hair, fibers and biological fluids are all potential evidence and need to be collected following established protocol. Time is of the essence and the potential for contamination or destruction should be a primary concern. Investigators must be familiar with the proper methods of collecting and protecting these items of evidence. 4. The Suspect and His Environment a. The suspect and his environment can be prime source of physical evidence. Just as the victim of a sexual assault will most likely possess physical evidence, the suspect is no different. Transfers of evidence readily occur and must be sought out on both the suspect’s vehicles or home. Again, time is of the essence and the potential for destruction or contamination is great. Investigator must always be on the alert for potential sources of physical evidence, such as the suspect’s vehicle, clothing, shoes, or even furniture in his home. VII. Comparison Evidence
A. Standards for Comparison 1. Most evidence found at a crime scene is of diminished value without a standard for camparison. Even the best fingerprint with the clearest characteristics is useless unless there is a rolled print to compare it to. 2. Finding evidence at the scene is only half the battle. The value or uniqueness of that piece of evidence must be proven in such a way that it provides a basis for logical conclusion; i.e., the fingerprint had to be deposited at scene by the suspect. 3. The investigator must also obtain the needed standards for comparison. If some foreign fibers were discovered at the scene of a crime, the investigator must be able to locate material that can be used for comparison; i.e., a shirt or jacket from the suspect that has a similar fabric and color. 4. Examples of comparison Evidence a. A shoe print only yields general information about the shoe that makes the print, unless the investigator can compare it to the suspect’s shoes. b. Hair evidence gives the most information when it can compared to that of the victim or suspect. c. A recovered projectile (bullet) will yield the most information when checked against a suspect’s firearm. IX. Standard Reference Files and Collections A. Nearly every crime laboratory maintains standard reference files and collections that used for comparison or informational purposes. For example, in the United States, the Federal Bureau of Investigation (FBI) Laboratory maintains the following standard files so that evidence can be compared: 1. Ammunition; 2. Check writer standards; 3. Duct tape/electrical tape; 4. Explosives and related items; 5. General rifling characteristics; 6. Hair and fibers; 7. National automotive image file; 8. National automotive paint file; 9. National motor vehicle certificate of title; 10. National motor vehicle altered numbers files; 11. National vehicle identification numbers file; 12. Office equipment standards (typewriters, copiers, printers, etc.); 13. Reference firearms collection; 14. Safe insulation; 15. Safety paper standards; 16. Shoe sole design standards; 17.Tire tread design standards; 18. Watermark standard; and, 19. Adhesives X. Terms to Be Familiar With A. Forensic Science 1. Forensic science is any science as it is applied to legal matters or to a presentation in a court of justice. For example: forensic pathology, forensic toxicology, forensic anthropology, forensic entomology, forensic chemistry, etc. B. Probable Cause 1. Probable cause is a factor or circumstance sufficient to convince a person of normal intelligence that a suspect was probably in a specific crime. C. Preponderance of Evidence 1. The preponderance of evidence is a combination of factors or circumstances which shows a high probability (greater than 50 percent) that a suspect was involved in a specific crime. Summary The value of physical evidence is determined by how useful it is in verifying that a crime has been committed, or that a person has been involved. Likewise, physical evidence can also exonerate a person who may be under suspicion. In this lesson we defined physical evidence and the general rules relating to its admissibility in a court of law. We learned that in addition to the scientific principles to which investigators adhere to, there are also legal requirements. Physical evidence acquired during a criminal investigation must satisfy legal standards and procedures to ensure its acceptability before the courts. In this lesson we also looked at the basic principles of evidence, such as individuality, class characteristics and similarity, probability, the exchange theory, and comparisons. All of these principles can used by an investigator to help prove the case.
Introduction to Trace Evidence
Lesson Goal The purpose of this lesson is to introduce the participants to the variety of trace evidence that can be found at a crime scene. Participants will examine the various properties of hair, fibers, glass, paint, and soil along with an overview of where these items are routinely found, and their evidentiary value in the investigation of a crime. Introduction One of the most common types of physical evidence that an investigator will encounter will be trace evidence. trace evidence is a generic terms for a small, often microscopic material. Trace evidence at a crime scene can include such obvious things as blood, hair, glass particles, or paint. Trace evidence can also include less obvious, or less thought of items such as minute fibers, or even soil. In this lesson, we are going to discuss the general properties of hair, fibers, glass, paint, and soil and look at the value of each as evidence. Blood will be discussed in a separate lesson. Presentation of Content I. Hair (human) NOTE: this section is making reference to the microscopic examination of hair and not a DNA examination. Hair is one of the most common types of trace evidence found at a crime scene. Next to teeth and bones, it is also one of the most decay-resistance human elements. A. Structurally, a hair is composed of: 1. The tip end
2. Cuticle 3. Cortex 4. Medulla 5. Bulb or root B. These items provide the laboratory examiner with definite information. Examination of the cuticle, cortex, or medulla may reveal any one of a number of personnel characteristics of its source.
1. Cuticle a. The cuticle is the outer surface of the hair and when viewed under a microscope appears composed of scale-like flakes, each overlapping the other similar to the overlapping of shingles on a roof or scales on a fish. These scales are known as cuticular scales.
2. Cortex a. The cortex is the inner portion of the hair and contains the pigmentation or coloring of the hair. 3. Medulla a. The medulla is the core or center portion of the hair shaft and, when magnified, appears as irregular, spinal, chain, or a continuous dark line of varying width, running up the center of the hair shaft. Note: Other important information may be gained through visual, microscopic, and chemical examinations of the tip end and bulb or roots of the hair.
C. The Value of Hair as Evidence
1. The value of hair as evidence in criminal cases has been clearly recognized. The microscopic examination of hair is seldom conclusive as evidence, but in conjunction with other details, has proven to be an important and essential aid to the investigator. The investigator must capitalize on the importance of this type of evidence during the initial phase of the investigation. The origin and texture of hair found at the crime scene, on a body, clothing, or headgear of a suspect or victim may be exceedingly important as evidence, particularly in homicides and sex crimes. Hair may be pulled out during the crime and found at the scene or on the victim. Hair transfer may be occur during any physical contact between the suspect and the victim. Hair may fall out under conditions that the suspect is not aware of and unable to guard against. Properly handled by the investigator, hair may provide excellent investigative leads and add to the evidentiary facts being assembled.
D. What Experts can determine by the microscopic examination of a human hair?
1. Characteristics of Races a. Mongoloid (round, producing straight and long hair) b. Caucasian (oval) c. Negroid (flattened) 2. Characteristics of Body Location a. Head hair (uniform diameter – for human hair) c. Facial hair; i.e., beards and mustaches (triangular) d. Public hair (irregular diameter) e. Armpits hair (irregular diameter) f. Rectal hair 3. Medullary Index (ratio of medulla diameter to whole hair diameter) a. Human hair (roughly 1/3) b. Animal hair (may be smaller or larger) c. Treatment or physical Changes d. If hair was forcibly removed e. If hair has been cut with a dull or sharp instrument (and possibly how long ago, if the hair continued to be subjected to friction or combing) f. If hair has been crushed or burned g. If hair has been dyed or bleached E. What cannot be Determine from the microscopic examination of a human hair? 1. Gender 2. Age 3. Positive individual identification F. Possible Conclusions Concerning Hair Sample Analyses 1. That the hairs match in terms of microscopic characteristics and that they originated from either the same individual or another individual whose hair exhibits the same microscopic characteristics. 2. That the hairs are not similar and did not originate from the same individuals. 3. That no conclusion can be reached. II Hair (Animal) A. All Mammals, (warm blooded creatures), have some type of hair, and of those most have two types of hair covering their body 1. Guard Hair a. Longer course hair that covers the upper side of the body to protect the animal from the elements 2. Fur Hair a. Shorter fine hair that thickly covers the bottom side of the animal body to provide insulation from the cold ground.
B. What Experts Can Determined from Examining an Animal Hair 1. The type of animal the hair originated from, such as a dog, cat horse, pig, goat, cow, etc. 2. The overall class characteristics such as overall diameter, length and color distribution. 3. If the hair is damaged in any way C. What Experts Cannot Determine from Examining an Animal hair 1. That the hair or hairs in question definitely originated from any one particular animal. D. Possible Conclusions Concerning Animal Hair Sample Analysis 1. That the sample in question matches the known animal hair samples in all major microscopic characteristics (length, overall diameter, color distribution) and that it may have originated from the animal or location in question 2. The sample is similar in some but not all microscopic characteristics and therefore may or may not have originated from the animal or location in question 3. That the sample is dissimilar in all microscopic characteristics and therefore did not originate from the animal in question E. The Value of Animal Hair Examination 1. The examination of Animal Hair will never provides an investigator with a positive form of identification. It will provides strong circumstantial evidence, and when combined with other forms of positive and incriminating facts and physical evidence, can assist in building a stronger case. III. Fibers A. A fiber (or filament) is the smallest single unit forming the basis of the textile yarn. A yarn is composed of numerous fibers that are spun, twisted, or drawn together to prepare the unit for weaving or knitting. A yarns is sometimes called a thread by the layman. B. Classes of Fibers – Fibers may be divided into the following classes: 1. Animal a. A number of fibers are derived from animals, the most important being wool, silk, camel’s hair, and fur. 2. Vegetable a. This class includes cotton, linen, jute, hemp, ramie, and sisal. 3. Mineral a. Minerals provide fibers such as glass, wool, and asbestos. 4. Synthetics a. Chemistry has produced a number of fibers including rayon, nylon, orlon, and Dacron. Note: Additional classifications vary greatly as to color and type of processing, yarn and thread composition, and end use. Fabrics, tapes, ropes, and similar end products may be subjected to fiber examination and instrumental analysis. C. Fibers Evidence a Valuable Aid to the Investigator The value of fibers as evidence in criminal cases has been widely recognized. Fibers evidence is seldom conclusive by itself, but in conjunction with other details or evidence, it has often proven to be an important and valuable aid to the investigator. The investigator must make every effort to maximize the possible use of fibers as evidence during the investigation. D. Fabric Transfer Contact between two pieces of fabric seldom can be made without an interchange of fiber material. In cases involving physical contact, both the victim’s and suspect’s clothing may intermingle and exchange fibers. In burglary cases, any contact with objects should also be considered in the examination of the crime scene and suspect’s clothing for fiber evidence. Points of entry such as window’s access to roofs, ladders, or drain pipes may reveal traces of fibers that are valuable to the investigation. Fibers from clothing and automobile upholstery may be transferred from one to the other. E. Placing a Suspect at the Crime Scene Fibers evidence can help place a suspect at the scene of a crime. Fibers may unwittingly be left at the crime scene by the suspect. Later, a laboratory examiner may determine that these fibers originated from a article of clothing that was worn by the suspect, which may have been described by the victim or witnesses. F. Transfer Between the Victim and Suspect Fiber evidence may also be interchanged between the victim and the suspect, particularly during crimes of violence such as rape, assault, or murder. This interchange can also help prove that the suspect and the victim were in each other’s presence. Such convincing evidence can severely attack the credibility of a rapist’s alibi, particularly when it is claimed that the victim was never in his presence. G. What Can be Determined by Examining Fibers? 1. Fibers From an Unknown Source a. Fibers from an unknown source can be identified by comparison with known specimens. Bits of yarn can be examined as to composition, dye content, and twist and ply count. When actual fragments of cloth are available, comparisons can be made as to dimension, shape, color, cloth type, dye pattern, thread count, and direction of twist of the threads. String is identified in much the same manner as yarn from cloth or other fabrics. 2. Fabric Composed of Knotted or Woven Yarns a. Fabric that is composed of knotted or woven yarns (fibers twisted together) can be grossly examined in terms of color, composition, and construction. Questioned fabrics can be determined to be similar to known fabrics. Positive identification can be made when a questioned piece of fabric may be fitted back into the known fabric. This type of fabric examination is based on matching broken ends of yarn together. 3. Tape Examination a. Similar to fabric examination, tape examination generally involves matching ends of pieces of tape used at the scene of a crime with the end of tape on a roll found in the suspect’s possession. 4. Rope and String Examination a. Cordage, in the form of rope and string, is examined in terms of composition, color, diameter, and construction. Rope can be identified by the angle at which the strands are twisted, the circumference, number of strands, number of yarns per strand, number of fibers per yarn, and chemical processing involving sizing, lubricants, preservatives, and insect repellents. The known source will be compared with be compared with the unknown, and occasionally ends may be matched or the manufacturer determined.
IV. Glass A. Glass is normally a fused mixture of silica, usually in the form of natural sand and two or more alkaline bases such as soda, lime, or potash. Glass also contains qualities of various other elements and metals, present either as accidental impurities in the basic ingredients, or added to them for color, degree of hardness, heat-resistance, and other specific purposes. These ingredients are melted in a crucible under very high temperatures, and the molten mass is then either rolled, blown, or molded into desired sizes and shapes. It may be later polished, ground, or cut for useful or decorative purposes, or it may be combined with other materials. For example, safety glass is formed by fusing sheet vinyl plastic between sheets of plain glass, and boron is added provide greater resistance to temperature (i.e., Pyrex glass) B. Visual Distinctions of Glass 1. When one looks at a piece of glass there are several distinctions that can be readily observed with the naked eye. These include: a. Color; b. Thickness; c. Curvature (if any); and, d. Surface texture. 2. Glass is very unique, since there can be thousands of different formulas in the glass making process. From simple pane glass to the wide variety of colored glass, each has its own physical properties that make it unique. For example, metals can be added to make the various colors: a. Iron = Greenish; b. Copper = Bluish; c. Manganese = Brownish; and, d. Gold = Ruby red. 3. Each mixture of glass has its own density. Therefore, a laboratory can conduct glass analysis using density gradient tubes to further compare other fragment densities. Another nondestructive comparison is that of refractive index. Spectrographic analysis identifies the elemental composition of glass, but is destructive because it burns up the fragment being tested. C. Value of Glass as Evidence 1. Glass can have relatively high value as evidence because of the identifiable variations in its physical properties and methods of manufacture. The evidence value of glass is also enhanced by the fact that large fragments may frequently be physically matched. Such physical matches are positive or certain. However, a laboratory is limited in that it can can only conclude that particular glass evidence consisting of tiny granules “has the same composition” as the original glass. Unless a fragment can be perfectly fit into an original glass piece, a certain conclusion cannot be reached. D. What Can be Determined by Examining Glass? 1. Glass fractures and glass fragments can provide information which will allow certain determinations to be made. a. That a fragment of glass did or did not originate from a particular glass object that has been broken (i.e., a fragment of headlight lens found at the scene of a vehicle accident did or did not originate from a broken headlight of a suspect’s vehicle). b. That a fragment of glass originated from a particular kind of glass object, such as a headlight lens, eyeglass lens, or window pane. c. The origin and direction of a fracture, that is, what caused it and the direction from which the causative force came. d. In the event of multiple fractures, including bullets holes, the order in which the fractures occurred. e. The angle that a bullet struck a glass object. 2. By microscopic optical and density comparisons, glass particles can be identified or compared with glass from known source. 3. The laboratory expert cannot identify the source to the exclusion of other sources, however, it can be stated and demonstrated that it is highly improbable that the particles came from a source other than the matching known source. If two or more different sources can be matched, the conclusion is greatly enhanced. V. Paint A. When one thinks of paint, the first identifying characteristic that comes to mind is usually color. Color is determined by the use of various dyes or granules of pigment in the paint. Aside from color, paint also has a wide variety of other distinguishing characteristics. These include its general composition; i.e. oil-based, acrylic, water- based (latex), etc., as well as its texture and finish, such as flat, semi-gloss or gloss. All of these characteristics combined create a very unique paint signature. B. Value of Paint as Evidence 1. As previously noted, paint can be very distinctive in its characteristics. Likewise, paint, in any form, can be useful as clue material in an investigation. Paint evidence may be in the form of a chip from a dried paint surface, trace, smear, or intact on some object. Paint as physical evidence is most frequently involved in burglary and hit-and-run accident cases. 2. Whenever a suspect tries to force entry into a building, some type of instrument is likely to be used. If the object being forced is painted, chips of that paint may cling to the instrument being used, and may also fall onto the suspect’s clothing. Also, if the instrument being used is painted, some of the paint may be transferred to the object being forced open. Transfers of paint chips, or traces are equally probable in automobile collisions. 3. The sequence of paint layers and their thickness can also be used as identifiers. C. Paint as evidence may be observed at a crime scene or on the clothing of a suspect or victim, in one of the following forms: 1. Small flakes or chips 2. Traces of oxidized (chalking) paint 3. Smears from fresh paint 4. An intact painted surface or item D. What Can be Determined from Examining Paint?
1. Working from a small chip of paint left at a crime scene, the capability of a crime laboratory to do paint analyses, augmented by an automotive paint file that it maintains, can often provide valuable investigative leads toward identification of the year, make, and color of a motor vehicle.
2. Paint on a tool can often be identified as having the same properties or composition as the standard taken from a door that was jimmied to gain entry during a burglary. 3. Paint is usually examined by comparing a sample recovered from a search to a known standard of paint. Paint chips can also be examined for a physical match with a part of a painted surface, attempting to match up the broken edges, scratches, or blemishes in the larger surface to any that may be discernible on the samples collected. Physical matching also involves making comparisons between texture, coloring, discolorations, layering, and other characteristics that may help to establish identity or source of the sample. The laboratory can also perform certain chemicals examinations of a paint sample, which can only prove similarity or dissimilarity. VI. Soil and Rocks A. Soils and rocks vary in different locations throughout the world. Differences can also be found within small local areas. The differences between two types of soil, such as sand and clay, may be easily recognized. However, detailed differences and similarities between samples of similar soil or rocks can only be detected by qualified laboratory chemists. Many variations of soil and rock have been caused by man. In mining, agricultural, and industrial areas there is an almost constant mixing and moving of soil and rocks, and materials and minerals are added to and taken from soil. Soil and rocks are also added to or taken away from surfaces to make them level, which disturbs the local geological patterns and taken further adds to the vast variety of soil and rock differences. B. Value of Soil and Rocks as Evidence 1. Soils, rocks, and other minerals may be found: a. On the suspect; b. On the suspect’s shoes; c. On the suspect’s clothing; d. In the suspect’s vehicle; e. On tools used in the crime; f. At the scene of the crime; g. On the victim C. These materials can provide valuable circumstantial evidence. However, such evidence is often overlooked because the investigator is neither aware of its potential value nor of the laboratory services available to make comparisons. Soil cannot be positively identified as coming from one source to the exclusion of all others, but the laboratory experts can associate questioned soil with a most probable source, conclude that a source cannot be eliminated, or that a point or area could not be the source of the questioned soil. These conclusions have proven extremely valuable in proving criminal cases. D. Soil and rock evidence can be derived in the several ways. 1. The suspect may carry and leave small amounts of rock and soil at the crime scene. 2. The suspect may pick up soil and rock materials at the crime scene. 3. The suspect may both leave and pick up soil and rock evidence. 4. In a hit-and-run accident, the suspect or his vehicle may pick up and leave soil and rock evidence. The impact of the collision may dislodge dirt and mud that had accumulated on the undercarriage of the suspect’s vehicle. Such particles can be found on the road or on the body or clothing of the victim who was struck by the vehicle. The suspect’s vehicle may have also run off the road, and in doing so, picked up mud and dirt on its tries and undercarriage that can prove the vehicle was at the accident scene.
Summary One of the most common types of physical evidence found at a crime scene is trace evidence, a generic term for small, often microscopic material. In this lesson we discussed some of the types of trace evidence that an investigator will encounter at a crime scene. These include hair, fibers, glass, paint, and soil. We looked at the general properties of each one of these types of trace evidence and the value of each of them as evidence. Throughout the lesson we learned how the various forms of trace evidence present unique detection problems. We also learned that due to the small and often microscopic size of this form of evidence, great care must be exercised to prevent loss or destruction of trace evidence.
Introduction to Fingerprint Evidence
Establishing the identity of a suspect of victim is one of the most important purposes of physical evidence. The most positive means of identifying people is through fingerprints. Fingerprints form on a person before birth and remain unchanged throughout life. With few exceptions, everyone has fingerprints. In this lesson, the term fingerprints includes all types of prints, including finger, palm, toe, and the sole of the foot. Locating and preserving fingerprints is one the most important responsibilities of an investigator when processing a crime scene.
One of the most valuable clues valuable clues at the scene of a crime is fingerprints. Fingerprints are markings that are left on a surface by a human hand and have the same markings as the skin of the fingers. Skin and ridge patterns are unique to each person. Unless their hands are covered with gloves or some other form of protection while committing a crime, criminals cannot avoid leaving clues in the form of fingerprints. Prints may be left when criminals take hold of an object or support themselves with their hands. Fingerprints sometimes appear in the form of a highly visible substance, such as blood, grease, oil, or ink.
A. Although we take it for granted today that identity can be positively established
Through fingerprints, the accurate and widespread use of this science is a product of the 20th century.
B. The Value of Fingerprints
1. Each Person Has Unique Skin and Ridge Patterns Skin and ridge patterns are unique to each person; therefore, everyone has a set of highly identifiable patterns. These patterns can be examined to produce an identification that is indisputable. No two individuals in the world have the same fingerprints. Not only are an individual’s characteristics unique, but the pattern never changes from birth to death. Any attempts to mutilate, remove, or alter fingerprints in any manner will not foil identification.
2. Characteristics About the Person Who Made Them To a certain degree, fingerprints may also reveal characteristics of the person who made them. For example, the hands of a brick layer or construction worker may reveal callouses and wear, while the hands of a brick layer or construction worker may reveal callouses observations are merely in addition to the basic fingerprint pattern and only enhance the uniqueness of the person’s fingerprints.
3. Only One Person Can Make a Given Impression Fingerprint evidence differs from most other evidence in that only one person, to the exclusion of all others in the world, can make a given impression. It is the uniqueness of the fingerprint that establishes beyond a reasonable doubt that a particular person made that fingerprint.
C. Formation of Fingerprints
Fingerprints are essential to criminal investigations. In order to fully understand the importance of fingerprints as a means of identification, it is necessary to have an understanding of how deep their formation runs through the various layers of skin tissue. The following section outlines the formation of fingerprints:
1. Epidermis a. The epidermis is the outer layer of skin, which actually makes up up the fingerprint impression. 2. Dermis a. The dermis is the layer just below the epidermis. 3. Papilla a. The papilla as the layer below the dermis. This is the deepest layer at which the unique fingerprints patterns can be reconstructed. If the fingerprint patterns on the surface are not clear due to serve burns, scarring, or injury, a skilled fingerprint technician can reconstruct the individual’s fingerprint to confirm someone’s identity. 4. Sweat Glands a. Underneath the skin’s surface, there are sweat glands that constantly lubricate the skin. The impression that we leave behind as a fingerprint is caused by perspiration escaping through sweat pores on the ridges of the skin. 5. Sebaceous Deposits a. Often, fingerprints occur as residue when the finger ridges have been contaminated with oil. Oil or sebaceous glands are not located in the fingers, but on other parts of the body. Most of the oil or grease found on our hands is actually due to touching other more oily parts of our body or greasy objects.
II. Types of Fingerprints
A. The three main types of fingerprints and their life expectancy are: 1. Latent Fingerprints a. Invisible Impressions Latent prints are invisible impressions that are left by persons and can be deposited on a variety of surfaces. Latent comes from a Latin word meaning “to lie hidden, to be concealed.” In order to make the fingerprint visible, it is necessary to develop the print. Latent fingerprints must be developed by dusting with fingerprint dusting powder, by chemical treatment, by “fuming” with fumes from burning.
iodine crystals, or fumes from cyanoacrylate (super glue), or by any other means of drawing out the prints and making them visible for collection by photographing or transferring to a transparent tape or similar substance. b. Have to Be Developed Latent prints also include any prints that are in any way visible or distinguishable but have to be developed before they can be examined properly. In most case, latent prints are found on objects with polished or smooth surfaces, and on paper. c. Life Expectancy When left on glass and other smooth objects, latent prints can remain for years if they are in a well-protected location. If an object is in the open air, prints can be develop several months after they are made. Prints, on paper are extremely stable and will last for years if the paper does not become wet and deteriorate. 2. Visible Fingerprints a. Completely Visible and Need Do Development Visible prints are prints of fingers or feet that are contaminated with foreign matter and need no development to be completely visible to the viewer. They may be found in dust or blood, or on any smooth and flat surface the suspect may have touched with the ridged parts of the hands or feet when they contained ink or some other substance that might serve as a “printing” medium when coming into contact with the surface. b. Life Expectancy Fingerprints that have resulted from contamination of the fingers with soot, dirt, flour, face powder, etc., are soon destroyed. Fingerprints that are contaminated with blood, ink, pigments, and and oil are more resistant and can last for a long time under favorable conditions. 3. Plastic Fingerprints a. Impression is Produced Plastic fingerprints occur when fingers touch or press against a plastic material in such a way that an impression of the friction ridge pattern is produced. Plastic prints are usually found in soft, pliable substances, such as putty, wax, soap, butter, or grease. Plastic prints can also be found in paint on a newly painted object, in the gum on envelopes and stamps, on adhesive tape, and on substances that melt easily or soften when they are held in hand. b. Life Expectancy These prints can remain on an object for any length of time, provided that the object on which they are left, or the substance in which they are formed, is itself stable.
III. The Fingerprint Pattern
A. The three basic characteristics in a fingerprint pattern are: 1. Type Lines a. The two innermost ridges which start parallel, diverge, and tend to surround the entire pattern area. 2. Delta a. That point on a ridge, at or in front of, the center of divergence of the type lines. 3. Core a. The approximate center of a fingerprint. IV. Classification Designations of Fingerprint Patterns A. There are three basic classification designations of fingerprint patterns, each of which are further classified into different types: 1. Arches a. Plain Arch – The ridges enter on one side of the impression and flow or tend to flow out the other side with a rise or wave in the center. b. Tented Arch – It is similar to a plain arch, with the exception that the ridges in center form a definite angle, or one or more ridges at the center form an upthrust; or they approach the loop but lacking in the third.
A loop has one or more ridges that enter on either side of the impression, recurve, touch, or pass an imaginary line drawn from the delta to the core, and fingerprints tend to terminate on or toward the same side of the impression from which the ridge(s) entered. a. Ulnar Loops – Those types of patterns in which the loops flow in the direction of the little fingers. b. Radial Loops – Those types of patterns in which the loop flow toward the thumbs. 3. Whorls Whorls are those types of patterns in which the ridges form concentric circles or spirals, or some variant of this geometric form. For the purposes of fingerprint classification, there are four types of whorl patterns. To the untrained eye all of those patterns will appear to be very similar. The following description of a whorl is sufficient for this training: a. Plain Whorls – Has two deltas and at least one ridge making a complete circuit, which may be spiral, oval, or any variant of the circle. An imaginary line drawn between the two deltas must touch or cross at least one of the recurving ridges within the pattern area.
V. Searching For and Collecting Fingerprints A. Conduct a Thorough Search for Fingerprints Extraordinary efforts should be made by a crime scene investigator to recover fingerprints because they are very valuable evidence. The investigator should make a through search of all surface areas in and around the crime scene that have the have the potential of retaining fingerprints. Special attention should be paid to the less obvious places such the undersides of toilet seats, table tops, dresser drawers, filing cabinets, the backs of chairs, rearview mirrors and the trunk lids of vehicles. Door knobs or telephones that are heavily handled objects may not yield good prints, however, they should always be processed. It is extremely important that the First Police Responder understand and appreciate the importance of fingerprint evidence. A well preserved crime scene is the most important step toward a successful crime scene search.
B. Developing Techniques for Latent Fingerprints 1. Developing with Powders a. This is when fingerprint powder, often referred to as dusting powder, is brushed over a latent print. Powders are used for impressions left on nonporous or nonabsorbent surfaces, which are smooth (i.e., glass, metal, porcelain). The print then becomes fully visible. There are numerous types of fingerprint powders and the the type used is determined by the color of the background and the nature of the surface. Black fingerprint powder is a universal developer on smooth, nonporous surfaces.
C. Chemical Fuming 1. When at all possible, chemical fuming should be done using a commercial fuming cabinet. However, there are other methods that can be employed in the field. These include use of a large clear plastic bag, or a jar which the evidence is inserted into and then fumed. Another method is to use an old aquarium with some type of cover, such as a piece of cardboard, glass, or wood, to hold in the chemical fumes until the prints are developed. Regardless of the methods, care should be taken not to inhale the fumes, since they can be a health hazard. a. Iodine Fuming - iodine crystals react with grease and oils when heated b. Cyanoacrylate (super glue) Fuming - Fumes cause latent fingerprint ridge patterns to become visible prints that appear white. Prints can then dusted and photographed. Used on nonporous surfaces to produce visible prints that appear white. The visible prints may be dusted with powder, photographed and lifted. Used successfully for the development of latent prints on surfaces as diverse as plastics, electrical tape, garbage bags, styrofoam, aluminum foil, finished and unfinished wood, rubber, copper, cellophane, rubber bands, and smooth rocks.
D. Other Chemical Processes The application of these chemicals to develop latent fingerprints is normally accomplished through the application of the chemical in liquid solution either through brush, spray, or immersion. 1. Ninhydrin – Reacts with amino acids to form a purple colored compound. Used with porous surfaces. 2. Amido Black – A protein stain that turns proteins that are present in blood to blue-black color 3. Silver Nitrate Reagent – reacts with the chloride (salts) present the fingerprint deposit. 4. Physical Developer – This is a photographic process that is based on formation of silver and a ferrous/ferric redox couple and the deposition of metal salts onto an image of a latent fingerprint.
E. Alternative Light Sources (ALS’s) The use of alternative light sources has become an important adjunct to locating and visualizing latent fingerprints, as well as other types of physical evidence such as trace evidence and certain types of biological evidence F. Elimination Prints It is very likely that the majority of fingerprints found and developed at the scene of a crime have been left by persons who had legitimate access to the premises. It is very important that these fingerprints be eliminated so that the examination may be concentrated on the remaining prints. The investigator should take elimination prints of all persons who are, or were on the premises and should submit them to the fingerprint examiner along with the prints that are lifted from the crime scene.
This lesson showed how valuable fingerprints can be to the investigator. Fingerprints are the most positive means of identifying people. Fingerprints form on a person before birth and remain unchanged throughout life. An investigator must be able to recognize the various types of fingerprints that can be found at the scene of a crime and be able to properly preserve and collect them. The investigator must also realize the vast number of locations that latent fingerprints might be located. These tasks are fundamental for an investigator to be successful and, in turn, help successfully solve and prosecute a variety of crimes.
It is extremely important for all First Police Responders to have an understanding and appreciation for the importance of crime scene preservation. The ultimate responsibility of assuring the integrity of potential physical evidence, prior to the arrival of trained evidence technicians, rest solely on the shoulders of the First Police Responder. This is an awesome responsibility and is not to be taken lightly.
Introduction to Physiological Fluids
Forensic serology is the identification of body fluids, usually in the form of stains on clothing or other crime scene evidence. Blood, semen, and saliva are the most valuable and commonly identified stains. Stains need to be located and tested to show which body fluid is present, and confirmed to be human in origin. Examination of such physical evidence is a crucial part of the crime scene and laboratory process. In this chapter participants will not learn only the value of physiological evidence, but also the probable locations of such evidence and methods to help assure the preservation of such evidence.
I. Forensic Serology
Forensic serology is the identification of bodily fluids, usually in the form of stains
on clothing or other crime scene evidence. The most valuable and most commonly identification bodily fluids found at crime scenes are stains created by blood, semen and saliva. Evidence from violent crimes such as murder, rape, assault, and robbery usually bear some of these bodily fluids. Investigators should never overlook the importance of these invaluable fluids or stains created by them. They should always be collected and submitted for subsequent serological analysis.
B. Types of Physiological Fluid Evidence
1. Blood Blood is the most common physical evidence found at the scene of a crime. It can be deposited in the form of trace amounts, drops, smears, or small pools. 2. Semen and Vaginal Secretions Semen and vaginal secretions are the next most common type of physiological fluid encountered in the investigation of crime, usually in connection with sexual assault and rape cases. When wet, semen is grayish- white in color and bears a chlorine-like odor. When dry, it is stiff and starch- like in consistency. 3. Saliva As evidence, saliva comes into play when samples are collected from suspects and victims. At the crime scene, saliva can be found on cigarette butts, cups, glasses, toothpicks, and other items placed in the mouth. 4. Urine Urine is ordinarily associated with some sex offenses and breaking and entering. If sufficient quantity exists, it is possible to distinguish between animal and human origin, as well as the alcohol content of the contributor. 5. Feces Feces is occasionally encountered at the scene of some crimes and the reason for this is a matter of differing opinion. Some individuals believe that it may have to do with nervousness, while others believe that it may be a sign of contempt towards the property owner or the police.
6. Vomitus Vomitus is not frequently encountered at the crime scene; however, if present, it can provide some limited information for the investigator. Aside from any laboratory testing, it may reveal some clues regarding the time and content of the contributor’s last meal. It may also provide clues about the person’s medical condition.
Perspiration can frequently be on articles of clothing. If the suspect discards any items of clothing, they can be collected and submitted for analysis. Although this bodily fluid is generally found in limited quantity, consideration for analysis should not overlooked. 8. Tears Tears are one of the least common forms of physiological fluid evidence found at a crime scene. Although tears do have serological value, their limited presence and quantity greatly diminish this value.
History of Serology Many
significant advances in the forensic sciences have been made in the field of serology. 1. 1800s The early history of forensic serology
can be traced to the late nineteenth century.
At that time, researchers were primarily concerned with the
development of chemical techniques to establish if a stain was in fact
blood of human origin. 2. 1900’s a.
Early 1900’s In 1901, a presumptive color change
test, for use on substances thought to be blood (called phenolphthalein) was
developed by Kastle and Sheed. This color presumptive test is still
in use today around the world. In the same year, German scientist Uhlenhuth
developed the precipitation test for distinguishing human and animal
blood. This was the first application of
serology to forensic science wherein
results were later introduced in a court of law. Likewise, Karl Landsteiner in
II. ABO Blood Typing Early forensic serology was limited to blood typing. Blood typing of the human population is commonly referred to as ABO typing. This is the same typing system used by blood banks all over the blood. Today, ABO typing is not used as commonly to classify blood or other bodily fluids as it was earlier. For decades, ABO blood typing has been used in criminal cases, however, it has its limitations and drawbacks.
A. Blood Types (Phenotypes) 1. A 2. B 3. O 4. AB B. Population Breakdown The following is a breakdown of the four (4) phenotypes in the general population:
Type % of Population
A 35% B 10% C 40% D 5% C. Limitations of ABO Testing 1. It is labor-intensive 2. Relying strictly on ABO typing, the forensic serologist will only be able to say that the suspect cannot be excluded as a source of the blood. ABO blood typing does little to provide positive indentification of a blood sample as having come from one individual to the exclusion of all others. ABO typing can only provide the investigator with the phenotype, or basic classification type of the contributor. 3. Interpretation of the typing is difficult. It is a rather simple matter to differentiate the source of blood if the victim and suspect have different blood types. However, if the types are the same for both the victim and suspect, the interpretation of the tying results is limited. D. Secreters and Non-Secreters Techniques exist in the laboratory to determine which blood enzymes
or proteins are present
in addition to the ABO typing. This is
important to the forensic serologist in that it enables the
laboratory to better differentiate
between blood groups from two or more subjects.
While the blood of all humans can
be grouped into one of the ABO and enzymes classifications,
not all persons have specific substances in sufficient quantity to allow their other body fluids to be grouped. Some individuals are secreters while
others are non-secreters. 1.
Secreters Secreters show evidence of their ABO typing
in their blood and in other bodily fluids (saliva, semen, vaginal
secretions, and perspiration).
Thus, it is possible to determine
the ABO blood group from a bite mark, a cigarette butt, or from seminal fluid in
a sexual assault case. Research has establish that the
concentration of the grouping factors in saliva and semen secretions are relatively
high, while their concentration in tears, urine,
and perspiration is very low. Saliva is
most suitable material for distinguishing a secretor from a non-secretor
. About 65 to 80 percent of the population
are secreters. 2.
Non-Secreters Individuals who are non-secreters show no
evidence of their blood type in their bodily fluids. Their blood can be grouped, but other body
fluids cannot. E.
Value of Secretion Identification In sexual assault cases, secretion
identification is most valuable. A vaginal
smear specimen will be typed and the evaluated with the blood typed
and secretor status of the victim and the suspect. The most definitive conclusion that can drawn is that
the suspect’s blood type is not consistent with the blood type determined
from the vaginal specimen. Stating that the suspect was definitely
responsible for depositing the semen is never possible with this test. III.
DNA (DeoxyriboNucleic Acid) A.
Forensic DNA Typing DNA is a molecule that makes up the
biochemical code included in the nucleus of every cell of an
individual. It is what makes a person
Approximately 98% of our DNA is identical among humans. The other 2% of our DNA contains the information that
is unique to an individual. B. Elaboration on Deoxyribonucleic Acid
(DNA) 1. Chromosomes DNA is the genetic material carried by
each living organism. Inside each of the 60 trillion cells in human
body are strands of genetic material called chromosomes. In humans, there are 23 pairs (46)
Genes Arranged along the chromosomes (which are made of the DNA molecule)
are approximately 100,000 genes. The
gene is the fundamental unit of
heredity. It instructs the body cells to
make proteins that determine all of our individual characteristics including eye color, hair color, susceptibility to diseases, etc.
3. Heredity DNA molecules are
replicated in the cell and the copies are transmitted from generation. This is known as inheritance.
One half of your DNA is inherited from your mother and half from
your father. With the exception
of identical twins, no two people share the same DNA. 4.
Structure of DNA DNA is complex molecule that forms a
double-helix structure that can be thought of as a twisted ladder
or a spiral staircase. The “railing” of the staircase is often
referred to as the “backbone” of the .
molecule. The “step” are
composed of pairs of chemicals called nucleotides or “bases.”
5. Function of DNA Between 1944 and 1952,
experimentation with bacteria and viruses began
to indicate that DNA was responsible for transmitting genetic information.
In 1953, James Watson and Francis Crick deduced physical structure of DNA and its role in genetics.
6. DNA in Forensic Science DNA “fingerprinting” was developed by
British biologist, Sir Alec Jeffreys at
Two murders had occurred, one in 1983 and one in 1986. In both murders, a young woman was raped and strangled while walking in an isolated area. After the second murder, police arrested a 17-year-old man who worked as a kitchen porter at a mental hospital. Jeffreys analyzed the semen samples from both victims and concluded that one individual was the source of both semen samples, and the accused kitchen porter was excluded as the source of the source of the semen. Police collected blood samples from 5512 local male residents to find a match. One individual, Colin Pitchfork, drew suspicion when he had a friend give his blood and pose as Pitchfork. Pitchfork was arrested, his blood sample was taken and matched that of the semen stains. This was the start of the police relying on DNA testing to confirm the identity of a suspect. C. Other Uses of DNA Testing DNA testing has been used for many years for paternity testing, tissue typing for organ transplants, archeology in tracing population genetics or family lineage, etc. DNA testing has also been used to identify the remains of military members who were recovered years after their death. D. Types of DNA Testing DNA analysis is the biochemical profile of an individual. The more points in the DNA code that are characterized, the closer the description is to being unique for that individual. Currently, most DNA testing falls short of absolute identification. There are data bases that list the rate of occurrence of specific DNA markers. When a given profile is compared with such a data base, an approximate rate of occurrence in the general population can be assessed. Therefore, a DNA profile “match” always comes with some statistical advice about how often this profile shows up. IV. Collection of Physiological Evidence The collection of any physiological fluid or stain that may be subjected to serological or DNA analysis must be collected in a manner that will preserve the quality and integrity of that evidence. A. Collection Techniques Generally, biological stains should be collected in the most concentrated and complete format that is possible. Common methods used to collect physiological evidence at the crime scene are as follows: 1. Collection of the Entire Object If an article that contains or may contain biological evidence can be easily collected, the entire item should be collected. 2. Removal of the Stain and the Surrounding Material If the entire object cannot be collected, the portion that contains the questioned stain should be removed and collected. 3. Scraping If a dried stain can be readily scraped from a surface (such as a laminated counter top or the surface of a kitchen appliance), the stain should be scraped into a pharmacy fold and sealed. 4. Swabbing One to four pre-packaged, sterile, wooden-shafted cotton swabs should be used to collect stains from most surfaces. The minimum number of swabs that are necessary to collect the entire stain will will be used. a. Dry Stains If the stain is dry, the swab(s) will first have to be moistened two drops of distilled water from a dropper bottle (do not dip swab into a bottle). A final swab will be used to remove all remaining moisture. b. Wet Stains Wet stains should be contacted directly with the common swabs for collection. Extremely large stains can normally have a representative sample collected on four swabs that will accommodate any forensic testing needs. B. Use of Personal Protective Equipment The use of personal protective equipment is necessary for the protection of the police officer against any biohazardous pathogens that may be contacted. Likewise, the intergrity of the evidence is ensured against any inadvertent contamination of the evidence or the crime scene by the collector or others present. It is crucial that any movement of a police officer between critical areas occur only if the officer and his equipment has been thoroughly decontaminated and new personal protective equipment is used to enter a new area. Critical area movement includes movement from a crime scene to a suspect’s residence, from a victim’s person to a suspect, etc. Utilizing these precautions prevents cross- contamination of evidence. Types of protective equipment are as follows: 1. Latex Gloves Gloves should be changed frequently to avoid the inadvertent transfer of physiological stain/fluids. Remember, a gloved hand provides a secondary surface that can provide a means to transfer DNA or other evidence to another object. Change gloves whenever a new or different task is carried out. 2. Tyvek Coveralls Coveralls of an impervious material should be worn whenever conditions exist that the clothing of the investigator can be contaminated or can cause contamination to the surroundings at a crime scene. These coveralls should be placed into a biohazard disposal bag prior to leaving the scene. 3. Shoe Covers If biohazardous conditions exist, shoe covers should be worn. Shoe covers should be changed whenever the crime scene is re-entered or during the movement between contaminated and uncontaminated areas or critical areas within the scene boundaries.
V. Bloodstain Pattern Evidence Blood is very frequently encountered at crime scenes, particularly those of a violent nature. By closely analyzing the bloodstain pattern left at the crime scene, there is information to be gained that extends beyond the various serological analyses previously discussed. As it is deposited, blood creates a pattern and provides a basis for study and interpretation. The First Police Responder must understand that any movement of objects, or bodies, at crime scene, prior to the arrival of an evidence technician and primary investigator, can alter and/or destroy potential findings. Such activities are strictly prohibited. A. Possible Determinations The following are possible determinations made from bloodstain evidence analysis: 1. The course and sequence of events that occurred during the commission of the crime
2. The nature of force, including the number of blows, the severity of blows, and the point of origin of a gunshot or a blow 3. The position of the participant and the distance between participants 4. Supportive or non-supportive analysis of the statements of victims, suspects, and witnesses, or of the conditions found at a crime scene (such as the position of the victim’s body or indications of a self-inflicted gunshot wound) 5. Information to be used in the interview or interrogation of witnesses or suspects 6. Logical determination for collection sites of blood samples for serological examinations
B. Blood Stain Properties 1. Physical Properties of Blood a. Consistency Regardless of the ambient temperature or the age, sex, or size of the contributor, blood will behave with consistent regularity when acted upon by gravity or other forces. b. Viscosity The property that resists the force tending to cause the fluid to flow. Blood has a relative viscosity of 3.6 – 5.4 (water is 1.0). 2. Blood Drop a. Size The smaller the orifice that expels the drop, the smaller the drop (up to a point). Conversely, the greater the surface area of the object on which the drop is formed, the larger the drop (up to a point). A wet or curved surface will produce a larger drop. Unless acted upon by outside forces, a drop of blood will fall when gravity overcomes the adhesive forces that tend to hold the drop together. b. Shape The volume of a drop falls in range depending on the variables involved, the average volume is 0.05 ml. Because of the cohesive forces of fluid dynamics, a drop of blood will as a sphere, not as a “teardrop” shape. c. Volume The larger the drop, the greater the volume. The greater the distance fallen and the higher the velocity, the larger the drop. 3. Clotting Time Clotting takes three to five minutes to begin. Clotting is slowed on irregular surfaces and at cooler temperatures. 4. Drying Time Subject to many variables such as temperature, humidity, air movement, volume of blood, size of the stain, and the surface that it is deposited on. Drying time for blood can range from approximately 40 minutes to 10 hours. C. Categories of Bloodstains 1. Falling/Dripping Blood falls or drips when overcome by the influence of gravity. These are characterized by larger, circular stains. 2. Projected Blood is projected when it is being propelled or expelled by a force greater that than gravity, such as: a. Blood that is cast off from a bloody object, such as a hatchet or hammer on the back swing. b. Blood being pumped through a breached artery by the action of the heart (arterial bleeding). 3. Contact a. Swipe A bloody object coming in contact with a non-bloody object. b. Wipe An object disturbing existing blood. c. Detail Characteristics can range from rough outline of the object to fine details (such as a bloody fingerprint) and/or “feathering” which are fine lines that indicate the direction of motion of the depositing contact. 4. Impact Blood being compressed by some force causing it to be broken into smaller droplets. These stains are characterized by various sizes and random distribution. a. Low Velocity Impact Splatter Splatter size 5 mm or more in diameter. This classification usually is caused by blood that is splashed onto a surface or blood that is subjected to a minor impact like stepping into blood or an object falling into blood. b. Medium Velocity Impact Splatter Splatter size is usually in the 1 to 4 mm range. Blood is usually subjected to a force between 5-25 feet/second. Medium velocity splatter is commonly associated with blunt force trauma. c. High Velocity Impact Splatter Splatter size is 1 mm or less. Blood is subjected to a force of 100 feet/second or greater. Many of the individual splatters are 0.01 mm or smaller and are created by a mist-like dispersion. Often associated with gunshots or explosions, this atomized mist, because of the low mass of the droplets, will usually only travel a short distance (less than a meter) before overcome by gravitational forces. The dispersion is often cone-shaped with the mist falling off quickly and the larger droplets traveling up to 6 feet away. d. Impact Angle Determination – Shape of Splatter . If blood strikes a surface perpendicular to its line of flight, a circular stain results. . If blood strikes a surface at an angle to its line of flight, an elongated stain will result. . The degree of elongation is proportional to the angle of impact (impact angle = arc sine (width/ length). This is useful in determination a three dimensional point of origin. . Directionality determination – the narrow ends of elongated splatter point in the direction of travel.
Practical Exercise # 2
Students will be shown four different crime scenes that will be displayed in a series of 35mm slides. Students will be allowed to ask questions, and will be required to take notes on each case. Students will be required to identify all items of potential physical evidence depicted in the slide presentations and record those observations in their notebook.