Crime Scene Paper
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4 Collection of Crime-Scene Evidence
F. Lukasseck/Jupiter Images
LEARNING OBJECTIVES
After studying this chapter, you should be able to:
• Define physical evidence.
• Review the common types of physical evidence encountered at crime scenes.
• Describe proper techniques for handling evidence to avoid damage or contamination.
• Understand collecting and packaging procedures for common types of physical evidence.
• Define and understand the concept of chain of custody.
• List the steps that are typically required to maintain appropriate health and safety standards at the
crime scene.
• Discuss the implications of the Mincey and Tyler cases.
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MURDER AND THE HORSE CHESTNUT TREE
Roger Severs was the son of a wealthy English couple, Eileen and Derek Severs, who were reported missing in 1983.
Police investigators were greeted at the Severs home by Roger, who at first explained that his parents had decided to
spend some time in London. Suspicion of foul play quickly arose when investigators located traces of blood in the
residence. More blood was found in Derek’s car and there were signs of blood spatter on the garage door. Curiously, a
number of green fibers were located throughout the house, as well as in the trunk of Derek’s car.
A thorough geological examination of soil and vegetation caked onto Severs’s car wheel rims seemed to indicate that
the car had been in a location at the edge of a wooded area. Closer examination of the debris also revealed the presence
of horse chestnut pollen. Horse chestnut is an exceptionally rare tree in the region of the Severs residence.
Using land maps, a geologist located possible areas where horse chestnut pollen might be found. In one of the
locations, investigators found a shallow grave that contained the bludgeoned bodies of the elder Severses. Not
surprisingly, they were wrapped in a green blanket. A jury rejected Roger’s defense of diminished capacity and found
him guilty of murder.
As automobiles run on gasoline, crime laboratories “run” on physical evidence . Physical evidence includes any and all
objects that can establish that a crime has or has not been committed or that can provide a link between a crime and its
victim or perpetrator.
physical evidence
Any object that can establish that a crime has or has not been committed or can link a crime and its victim or
perpetrator.
However, for physical evidence to aid the investigator, its presence must first be recognized at the crime scene. If
investigators were to gather all the natural and commercial objects within a reasonable distance of the scene so that the
scientist could uncover significant clues from them, the deluge of material into the crime laboratory would quickly
immobilize the facility. This is why it is important for investigators to be discriminating and to get it right the first
time. The collection of evidence must be thorough enough to include as many pertinent clues as possible but selective
enough not to bog down the laboratory. Physical evidence achieves its value in criminal investigations only when the
investigator collects it selectively and with a thorough knowledge of the crime laboratory’s techniques, capabilities,
and limitations.
Common Types of Physical Evidence
It would be impossible to list all the objects that could conceivably be important to a crime. Every crime scene has to
be treated on an individual basis, having its own peculiar history, circumstances, and problems. However, it is practical
to be aware of types of items whose scientific examination is likely to yield significant results in ascertaining the
nature and circumstances of a crime. The investigator who is thoroughly familiar with the recognition, collection, and
analysis of these items, as well as with laboratory procedures and capabilities, can make logical decisions when faced
with uncommon and unexpected circumstances at the crime scene. Equally important, a qualified evidence collector
cannot rely on collection procedures memorized from a pamphlet but must be able to make innovative, on-the-spot
decisions at the crime scene.
Blood, Semen, and Saliva
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All suspected blood, semen, or saliva—liquid or dried, animal or human—presents in a form that suggests a
relationship to the offense or people involved in a crime. This category includes blood or semen dried onto fabrics or
other objects, as well as cigarette butts that may contain saliva residues. These substances are subjected to serological
and biochemical analysis to determine identity and possible origin.
Documents
Any handwriting and typewriting submitted so that authenticity or source can be determined. Related items include
paper, ink, indented writings, obliterations, and burned or charred documents.
Drugs
Any substance in violation of laws regulating the sale, manufacture, distribution, and use of drugs.
Explosives
Any device containing an explosive charge, as well as all objects removed from the scene of an explosion that are
suspected to contain the residues of an explosive.
Fibers
Any natural or synthetic fiber whose transfer may be useful in establishing a relationship between objects and/or
people.
Fingerprints
All prints of this nature, hidden (latent) and visible.
Firearms and Ammunition
Any firearm, as well as discharged or intact ammunition, suspected of being involved in a criminal offense.
Glass
Any glass particle or fragment that may have been transferred to a person or object involved in a crime. This category
includes windowpanes containing holes made by a bullet or other projectile.
Hair
Any animal or human hair present that could link a person with a crime.
Impressions
Tire markings, shoe prints, depressions in soft soils, and all other forms of tracks. Glove and other fabric impressions,
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as well as bite marks in skin or foodstuffs, are also included in this category.
Organs and Physiological Fluids
Body organs and fluids submitted for analysis to detect the possible existence of drugs and poisons. This category
includes blood to be analyzed for the presence of alcohol and other drugs.
Paint
Any paint, liquid or dried, that may have been transferred from the surface of one object to another during the
commission of a crime. A common example is the transfer of paint from one vehicle to another during an automobile
collision.
Petroleum Products
Any petroleum product removed from a suspect or recovered from a crime scene. The most common examples are
gasoline residues removed from the scene of an arson and grease or oil stains whose presence may suggest
involvement in a crime.
Plastic Bags
A disposable polyethylene bag such as a garbage bag that may be evidential in a homicide or drug case. Examinations
are conducted to associate a bag with a similar bag in the possession of a suspect.
Plastic, Rubber, and Other Polymers
Remnants of these manufactured materials recovered at crime scenes may be linked to objects recovered in the
possession of a criminal suspect.
Powder Residues
Any item suspected of containing powder residues resulting from the discharge of a firearm (see Figure 4-1 ).
Serial Numbers
This category includes all stolen property submitted to the laboratory for the restoration of erased identification
numbers.
Soil and Minerals
All items containing soil or minerals that could link a person or object to a particular location. Common examples are
soil imbedded in shoes and insulation found on garments.
Tool Marks
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This category includes any object suspected of containing the impression of another object that served as a tool in a
crime. For example, a screwdriver or crowbar could produce tool marks by being impressed into or scraped along a
wall.
FIGURE 4-1 The gun is fired at a set distance from the target, and the
gun-powder left on the target is compared to powder stains on a victim’s
clothing. The density and shape of the powder stains vary with the
distance the gun was fired.
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Mikael Karlsson\Arresting Images Royalty Free
Vehicle Lights
The examination of vehicle headlights and taillights is normally conducted to determine whether a light was on or off
at the time of impact.
Wood and Other Vegetative Matter
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Any fragments of wood, sawdust, shavings, or vegetative matter discovered on clothing, shoes, or tools that could link
a person or object to a crime location.
Quick Review
• Biological crime-scene evidence includes blood, saliva, semen, DNA, hair, organs, and physiological fluids.
• Impression crime-scene evidence includes tire markings, shoe prints, depressions in soft soils, all other forms
of tracks, glove and other fabric impressions, tool marks, and bite marks.
• Manufactured items considered common items of crime-scene evidence include firearms, ammunition, fibers,
paint, glass, petroleum products, plastic bags, rubber, polymers, and vehicle headlights.
FIGURE 4-2 A typical evidence-collection kit.
Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com
Evidence-Collection Tools
The well-prepared evidence collector arrives at a crime scene with a large assortment of packaging materials and tools
ready to encounter any type of situation. These tools are usually kept in an evidence-collection kit (see Figure 4-2 ).
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FIGURE 4-3 Evidence flags are used for outdoor crime scenes.
Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com
• Notebook
• Pen (black or blue ink)
• Ruler
• Chalk or crayons
• Magnifying glass
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• Flashlight
• Disposable forceps and similar tools, which may be needed to pick up small items
• Scalpels or razor blades
• Swabs and medicine droppers for presumptive testing
• Gauze or sterile cloth
• Unbreakable plastic pill bottles with pressure lids
• Evidence sealing tape
• Evidence tags (indoor) or flags (outdoor) (see Figure 4-3 )
• Various size paper bags, boxes, and manila envelopes
• Red “biohazard” labels
• Paper for wrapping or for creating “druggist folds”
• Alternate light source (see Figure 4-4 )
• Lifting tape for gathering hair or trace evidence
• Vacuum collector with filters
• Fingerprint powders, brushes, and lifters
• Disposable gloves, face masks, and shoe covers
FIGURE 4-4 An example of an alternate light source in use. This can be
used to visually enhance many types of evidence.
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MOBILE CRIME LABORATORIES
In recent years, many police departments have gone to the expense of purchasing and equipping mobile crime
laboratories for their evidence technicians. However, the term mobile crime laboratory is a misnomer. These vehicles
carry the necessary supplies to protect the crime scene; to photograph, collect, and package physical evidence; and to
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perform latent print development. They are not designed to carry out the functions of a chemical laboratory. Crime-
scene search vehicle would be a more appropriate but perhaps less dramatic name for such a vehicle (see Figure 4-5 ).
Procedures for Collecting and Packaging Physical Evidence
Physical evidence can be anything from massive objects to microscopic traces. Many items of evidence are obvious
when present, but others may be detected only through examination in the crime laboratory. For example, minute
traces of blood may be discovered on garments only after a thorough search in the laboratory, or the presence of hairs
and fibers may be revealed in vacuum sweepings or on garments only after close laboratory scrutiny. For this reason,
investigators should collect possible carriers of trace evidence in addition to more discernible items. This may include
vacuum sweepings, fingernail scrapings, clothing, and vehicles.
FIGURE 4-5 An inside view of a mobile crime-scene van: (a) driver’s side
and (b) passenger’s side.
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The investigator should vacuum critical areas of the crime scene and submit the sweepings to the laboratory for
analysis. The sweepings from different areas must be collected and packaged separately. A portable vacuum cleaner
equipped with a special filter attachment is suitable for this purpose (see Figure 4-6 ). Fingernail scrapings from
individuals who were in contact with other individuals may contain minute fragments of evidence capable of providing
a link between assailant and victim. The investigator should scrape the undersurface of each nail with a dull object
such as a toothpick to avoid cutting the skin. These scrapings will be subjected to microscopic examination in the
laboratory. All clothing from the victim and suspect(s) should be collected and packaged separately. These objects will
be further examined at the laboratory for trace, fiber, and hair evidence.
When a vehicle is involved in a crime, investigators should pay particular attention to signs of a cross-transfer of
evidence between the car and the victim—this includes blood, tissue, hair, fibers, and fabric impressions. Traces of
paint or broken glass may be located on the victim or roadway. The entire car should be processed for fingerprints. In
cases in which the car was used for transportation, more attention may be given to the interior of the car. However, all
areas of the vehicle, inside and outside, should be searched with equal care for physical evidence.
FIGURE 4-6 A vacuum sweeper attachment, constructed of clear plastic
in two pieces that are joined by a threaded joint. A metal screen is
mounted in one half to support a filter paper to collect debris. The unit
attaches to the hose of the vacuum sweeper. After a designated area of the
crime scene is vacuumed, the filter paper is removed and retained for
laboratory examination.
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HANDLING EVIDENCE
Investigators must handle and process physical evidence in a way that prevents any changes in it between the time the
evidence is removed from the crime scene and the time it is received by the crime laboratory. Changes can arise
through contamination , breakage, evaporation, accidental scratching or bending, or improper or careless packaging.
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The use of latex gloves or disposable forceps when touching evidence often can prevent such problems. Any
equipment that is not disposable should be cleaned and/or sanitized between collection of each piece of evidence.
Evidence should remain unmoved until investigators have documented its location and appearance in notes, sketches,
and photographs.
contamination
The transfer of extraneous matter between the collector and the evidence or multiple pieces of evidence, producing
tainted evidence that cannot be used in the subsequent investigation.
Evidence best maintains its integrity when kept in its original condition as it was found at the crime site. Whenever
possible, one should submit intact evidence to the laboratory. The investigator normally should not remove blood,
hairs, fibers, soil particles, or other types of trace evidence from garments, weapons, or any other articles that bear
them. Instead, he or she should send the entire object to the laboratory for processing.
Of course, if evidence is adhering to an object in a precarious manner, good judgment dictates removing and packaging
the item. Investigators must use common sense when handling evidence adhering to a large structure, such as a door,
wall, or floor; they should remove the specimen with a forceps or other appropriate tool. In the case of a bloodstain,
the investigator may either scrape the stain off the surface, transfer the stain to a moistened swab, or cut out the area of
the object bearing the stain.
PACKAGING EVIDENCE
The well-prepared evidence collector arrives at a crime scene with a large assortment of packaging materials and tools,
ready to encounter any type of situation. Forceps and similar tools may be used to pick up small items. Unbreakable
plastic pill bottles with pressure lids are excellent containers for hairs, glass, fibers, and various other kinds of small or
trace evidence. Alternatively, manila envelopes, screw-cap glass vials, sealable plastic bags, and metal pillboxes are
adequate containers for most trace evidence encountered at crime sites (see Figure 4-7 ). Charred debris recovered from
the scene of a suspicious fire must be sealed in an airtight container to prevent the evaporation of volatile petroleum
residues. New paint cans or tightly sealed jars are recommended in such situations (see Figure 4-8 ).
Ordinary mailing envelopes should not be used as evidence containers, because powders and fine particles will leak
out of their corners. Instead, small amounts of trace evidence can be conveniently packaged in a carefully folded paper,
using what is known as a “druggist fold” (see Figure 4-9 ). This method consists of placing the evidence in the center of
a piece of paper, folding one-third of the piece of paper over the middle third (and the evidence), folding the opposite
end (one-third) over that, then repeating the process on the other two sides. After folding the paper in this manner, one
should tuck the outside two flaps into each other to produce a closed container that keeps the specimen from falling
out.
FIGURE 4-7 (a) A manila evidence envelope, (b) metal pillboxes, and (c) a
sealable plastic evidence bag.
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FIGURE 4-8 Airtight metal cans used to package arson evidence.
Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com
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FIGURE 4-9 A druggist fold is used to package paint transfer evidence.
Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com
Each different item or similar items collected at different locations should be placed in separate containers. Packaging
evidence separately prevents damage through contact and prevents cross-contamination.
BIOLOGICAL MATERIALS
Use only disposable tools to collect biological materials for packaging. If biological materials such as blood are stored
in airtight containers, the accumulation of moisture may encourage the growth of mold, which can destroy their
evidential value. In these instances, wrapping paper, manila envelopes, or paper bags are the recommended packaging
materials (see Figure 4-10 ). As a matter of routine, all items possibly containing biological fluid evidence should be
air-dried and placed individually in separate paper bags to ensure a constant circulation of air around them. This will
prevent the formation of mold and mildew. Paper packaging is easily written on, but seals may not be sturdy. Finally,
place a red biohazard sticker on both the secured evidence bag and the property receipt to ensure all handlers will be
aware the item is contaminated with biological fluids, such as blood, saliva, or semen.
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FIGURE 4-10 Paper bags and manila envelopes are recommended
evidence containers for biological evidence, especially objects suspected of
containing blood and semen stains. Each object should be packaged in a
separate bag or envelope.
Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com
The evidence collector must handle all body fluids and biologically stained materials as little as possible. All body
fluids must be assumed to be infectious, so investigators must wear disposable latex gloves while handling the
evidence. Latex gloves also significantly reduce the possibility that the evidence collector will contaminate the
evidence. Investigators should change gloves frequently during the evidence-collection phase of the investigation.
Safety and contamination considerations also dictate that evidence collectors wear face masks and shoe covers.
DNA EVIDENCE
The advent of DNA analysis brought one of the most significant recent advances in crime-scene investigation. This
technique is valuable for making it possible to identify suspects through detecting and analyzing minute quantities of
DNA deposited on evidence as a result of contact with saliva, sweat, or skin cells. The search for DNA evidence
should include any and all objects with which the suspect or victim may have come into bodily contact. Likely sources
of DNA evidence include stamps and envelopes that have been licked, a cup or can that has touched a person’s lips,
chewing gum, the sweatband of a hat, and a bedsheet containing dead skin cells.
One key concern during the collection of a DNA-containing specimen is contamination. Contamination—in this case,
introducing foreign DNA—can occur from coughing or sneezing onto evidence during the collection process. Transfer
of DNA can also occur when items of evidence are incorrectly placed in contact with each other during packaging. To
prevent contamination, the evidence collector must wear a face mask and use disposable latex gloves and disposable
forceps. The evidence collector may also consider wearing coveralls and shoe covers as an extra precaution to avoid
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contaminating DNA evidence.
Blood analysis has great evidential value when it allows the investigator to demonstrate a transfer between a victim
and a suspect. For this reason, all clothing from both the victim and suspect should be collected and sent to the
laboratory for examination, even when the presence of blood on a garment does not appear obvious to the investigator.
Laboratory search procedures are far more revealing and sensitive than any that can be conducted at the crime scene.
A detailed description of the proper collection and packaging of various types of physical evidence will be discussed in
forthcoming chapters; additionally, most of this information is summarized in the evidence guide found in Appendix I .
MAINTAINING THE CHAIN OF CUSTODY
Whenever evidence is presented in court as an exhibit, the investigator must establish continuity of possession, or the
chain of custody . This means that he or she must account for every person who handled or examined the evidence.
Failure to substantiate the evidence’s chain of custody may lead to serious questions regarding the authenticity and
integrity of the evidence and the examinations of it. Adhering to standard procedures in recording the location of
evidence, marking it for identification, and properly completing evidence-submission forms for laboratory analysis are
the best guarantee that the evidence will withstand inquiries about what happened to it from the time it was found to its
presentation in court.
chain of custody
A list of all people who came into possession of an item of evidence.
FIGURE 4-11 Proper evidence tape seals on evidence in various packages.
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Once an investigator selects an evidence container, he or she must mark it for identification. All evidence packages
must be labeled, and their openings must be sealed with evidence tape (see Figure 4-11 ). Evidence containers often
have a preprinted identification form for the evidence collector to fill out; otherwise, the collector must attach an
evidence tag to the container (see Figure 4-12 ). The investigator who packaged the evidence must write his or her
initials and the date on the evidence tape seal. Anyone who removes the evidence for further testing or observation at a
later time should try to avoid breaking the original seal if possible so that the information on the seal will not be lost.
The person who reseals the packaging should record his or her initials and the date on the new seal.
At a minimum, the record of the evidence that is used to demonstrate chain of custody shows the collector’s initials,
the location of the evidence, and the date of collection. Transfer of evidence to another individual or delivery to the
laboratory must be recorded in notes and other appropriate forms (see Figure 4-13 ). In fact, every individual who
possesses the evidence must maintain a written record of its acquisition and disposition. Frequently, all of the
individuals involved in the collection and transportation of the evidence must testify in court. Thus, to avoid confusion
and to retain complete control of the evidence at all times, the transfer of custody should be kept to a minimum.
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FIGURE 4-12 Examples of evidence tags that may be attached directly to
the evidence.
Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com
Failure to substantiate the evidence’s chain of custody may lead to serious questions regarding the authenticity and
integrity of the evidence and the examinations performed on it. Adhering to standard procedures when recording the
location of evidence, marking it for identification, and properly completing evidence-submission forms for laboratory
analysis is the best way to guarantee that the findings will withstand inquiries about the integrity of the evidence. If a
delay occurs between the time evidence is collected and the time it is submitted to the forensic laboratory, the
investigator must store the evidence in a secured area with only limited access by police personnel (see Figure 4-14 ).
FIGURE 4-13 A chain of custody form is used to record the name of every
person who handled or examined the collected evidence.
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OBTAINING STANDARD/REFERENCE SAMPLES
FIGURE 4-14 An example of a secure evidence locker.
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To examine evidence, whether soil, blood, glass, hair, or fibers, often the forensic scientist must compare it with a
sample of similar material whose origin is known. This is known as a standard or reference sample . Although most
investigators have little difficulty recognizing and collecting relevant crime-scene evidence, few seem aware of the
necessity and importance of providing the crime lab with a thorough sampling of standard/reference materials. Such
materials may be obtained from the victim, a suspect, or other known sources. For instance, investigation of a hit-and-
run incident might require the removal of standard/reference paint from a suspect vehicle. This will permit its
comparison to paint recovered at the scene.
standard/reference sample
Physical evidence whose origin is known, such as blood or hair from a suspect, that can be compared to crime-scene
evidence.
The presence of standard/reference samples greatly facilitates the work of the forensic scientist. For example, hair
found at a crime scene will be of optimum value only when compared to standard/reference hairs removed from the
suspect and victim. Likewise, bloodstained evidence must be accompanied by a whole-blood or buccal swab
standard/reference sample obtained from all relevant crime-scene participants. The quality and quantity of
standard/reference specimens often determines the evidential value of crime-scene evidence, and so must be treated
with equal care.
buccal swab
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A swab of the inner portion of the cheek; performed to collect cells for use in determining the DNA profile of an
individual.
Some types of evidence must also be accompanied by substrate controls . These are materials close to areas where
physical evidence has been deposited. For example, an arson investigator who suspects that a surface has been exposed
to an accelerant, such as gasoline, should collect a piece of the same surface material that he or she believes was not
exposed to the accelerant. At the laboratory, forensic scientists will first test the substrate control to see whether the
nature of the surface itself will interfere with the procedures used to detect and identify accelerants. Another common
example of a substrate control is a material containing a bloodstain. Unstained areas close to the stain may be sampled
to determine whether this material can interfere with the interpretation of laboratory results. Thorough collection and
proper packaging of standard/reference specimens and substrate controls are marks of a skilled investigator.
substrate controls
Surface material close to areas where physical evidence has been deposited.
SUBMITTING EVIDENCE
Evidence is usually submitted to the laboratory either personally or by mail. Although most evidence can be shipped
by mail, postal regulations restrict the shipment of certain chemicals and live ammunition and prohibit the mailing of
explosives. In such situations, one should consult the laboratory to determine the disposition of these substances. One
must also exercise care when packaging evidence in order to prevent breakage or other accidental destruction during
transit to the laboratory (see Figure 4-15 ). If the evidence is delivered personally, the deliverer should be familiar with
the case to facilitate any discussions with laboratory personnel concerning specific aspects of the case.
Most laboratories require that an evidence-submission form accompany all submitted evidence (see Figure 4-16 ). The
information on this form enables the laboratory analyst to make an intelligent and complete examination of the
evidence. Providing a brief description of the case history is particularly important. This information allows the
examiner to analyze the specimens in a logical sequence and make the proper comparisons; it also facilitates the search
for trace quantities of evidence.
The submission form should specify the particular kind of examination requested for each type of evidence. However,
the analyst is not bound to adhere strictly to the specific tests requested by the investigator. The discovery of new
evidence may dictate changes in the tests required, or the analyst may find the initial requests incomplete or not totally
relevant to the case. Items submitted for examination should be packaged separately and each item should be assigned
a number or letter. The evidence-submission form should list the items and their identifying numbers or letters in an
orderly and logical sequence.
FIGURE 4-15 Evidence that has been correctly packaged and labeled can
be sent through the mail.
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Once evidence is received, it will undergo the requested tests and examinations. When a piece of evidence has been
fully examined and tested, it must be submitted to long-term storage. The storage area and containers should be secure
to prevent tampering and maintain the chain of custody.
Quick Review
• Physical evidence includes any and all objects that can establish that a crime has been committed or can link
the crime and its victim or perpetrator.
• Many items of evidence may be detected only through examination of crime-scene materials at the crime
laboratory. For this reason, it is important to collect possible carriers of trace evidence, such as clothing, vacuum
sweepings, and fingernail scrapings, in addition to more discernable items.
• Each item of physical evidence collected at a crime scene must be placed in a separate, appropriate container to
prevent damage through contact and cross-contamination.
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• Investigators must maintain the chain of custody, a record for denoting the location of the evidence.
• Proper standard/reference samples must be collected at the crime scene and from appropriate subjects for
comparison purposes in the laboratory. Substrate controls must also be collected.
• Typically, an evidence-submission form accompanies all evidence submitted to the crime laboratory. The form
lists each item submitted for examination.
FIGURE 4-16 An example of a properly completed evidence-submission
form.
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Ensuring Crime-Scene Safety *
Safety is one of the most important responsibilities of an employee because it can affect one’s personal health. The
employer can implement rules and regulations; educate employees about the standard operating procedures, also
known as SOPs; and supply the proper equipment and resources, but it is the responsibility of the employee to enforce
these safety standards in the field. Standard operating procedures should be reviewed annually by all crime-scene
employees, and the agency should retain a record of reviews, which documents the date at which each employee
reviewed the standard operating procedures. Updates of current crime-scene safety regulations and education should be
provided annually by a designated crime-scene safety coordinator. Health inspections should also be included in the
job requirements of personnel who operate certain safety equipment used at the crime scenes. For example, before an
employee can wear a respirator at crime scenes, a physical health examination is required, and a proper fit must be
ensured.
*This section was contributed by and is used with the permission of Jan Johnson, Forensic Specialist; Certified IAI CSCSA; Retired State of
Florida; Forensic Pieces, Inc., and Natalie M. Borgan, MS; Certified IAI CCSI; Crime Scene Technician, Coral Gables Police Department.
PERSONAL PROTECTIVE EQUIPMENT (PPE)
RESPIRATORY PROTECTION
Respiratory protection is one of the most important types of personal protective equipment (PPE). Respiratory
protection can range from a disposable filter mask to a self-contained breathing apparatus, also known as SCBA. Every
crime-scene unit should have a training program that teaches employees about the different types of respiratory
protection so they will be able to choose the mask that is most appropriate for each crime scene. The most important
thing to remember when using a mask is to make sure it is properly sealed, which is the perfect fit. A proper seal
between the face and the respiratory mask prevents any chemicals or irritants from entering.
Crime-scene technicians or investigators should know the differences between the respiratory protections available for
use at different crime-scene environments. Dust particle masks or N-95 masks are used for routine crime scenes. They
are considered the most common type of respiratory protection. These masks are considered to be disposable and
should be discarded after one use. The half-face cartridge respirator can be a disposable model with a mechanical filter
or a reusable model with disposable filters. It is called a half-face cartridge respirator because it protects only the
bottom half of the face, including the mouth and nose. A power-assisted air-purifying respirator is a positive-pressure
system, which means that the air on the inside of the mask is at a higher pressure than the outside air pressure. This
type of respirator allows the wearer to control the air that passes through the respirator to reduce or increase the
amount of air that is filtered. Full-face respirators cover the entire face to protect the face and eyes from contaminants
while filtering the air. This type of mask works well to filter contaminants, such as chemicals, dust, and spores, from
the air the wearer breathes. First responders and firefighters especially benefit from these masks because they are in
contact with hazardous chemicals on a daily basis.
A self-contained breathing apparatus has a tank, a regulator, and inhalation piece. If someone is claustrophobic, he or
she would have a problem utilizing one of these respirators. Not all crime-scene personnel will be able to wear an
SCBA. Investigators must first undergo a health screening to detect possible lung issues.
EYE PROTECTION
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Eye protection is extremely important when a crime-scene worker is processing a crime scene where contaminants or
chemicals could get into his or her eyes. The crime-scene technician must wear goggles even if he or she is wearing
prescription glasses or contacts; glasses or contacts do not replace proper eye protection. If your eye comes into
contact with a chemical, rinse your eye with water for a minimum of 15 minutes. Chemical goggles are the best type of
goggles. Face shields are also considered eye protection, and goggles must be worn with them. If any type of laser is
being used at the crime scene, workers should wear the appropriate eye protection.
CHEMICAL PROTECTIVE CLOTHING
Tyvek protective clothing is inexpensive, chemical resistant, and disposable. Tyvek is difficult to tear but easy to cut.
In extreme temperatures, Tyvek should not be worn for longer than 15 minutes at a time: Because the material traps
heat, the wearer must take a break from the Tyvek to allow his or her body to readjust to the ambient temperature. If
the rest period is not provided, heat stroke and possible death may occur. Nomex brand protective clothing is fire
retardant but not fireproof; it can only resist flames of up to approximately 220 degrees Celsius. Neoprene protective
clothing has good chemical stability and is chemical resistant and waterproof. It is widely used and inexpensive. Butyl
rubber is a synthetic rubber that is a harder and less porous material than natural rubber, and although it is expensive, it
is used in boots, aprons, and gloves. Saranex material is chemical resistant and disposable. However, workers need to
be careful in hot conditions because heat stress can quickly become a serious problem when wearing this material.
Hand protection helps the crime-scene worker to avoid destroying and/or contaminating evidence while protecting him
or her from safety hazards. Gloves are essential when processing crime scenes. However, a crime-scene technician or
investigator needs to know the different types of gloves available and, after assessing the situation, which will be the
best for processing the scene. Gloves should be changed on a frequent basis during crime-scene processing, especially
when a glove has become soiled or to avoid cross-contamination when the investigator is about to collect a different
piece of evidence. Because gloves degrade over time, when gloves are purchased, the box should be dated and the box
with the oldest date should be used up first. Gloves will also degrade in extreme temperatures.
Polyvinyl gloves are thin, clear gloves that don’t provide any protection against chemicals or acids. These gloves are
fine for processing crime scenes with black powder and biological fluids. Latex gloves are especially good for
processing scenes with black powder and biological fluids. Because this type of glove is thin, gloves must discarded
after a single use. Latex is a relatively weak material, and the wearer must be alert for any pinholes, which can
undermine the integrity of the glove. It is not a bad idea to “double glove” when using latex gloves, but this will not
resolve the pinhole problem. There are individuals who are latex sensitive and therefore need to use a different type of
glove to avoid an allergic reaction. Allergic reactions should be taken seriously; they can result in serious injury or
even be fatal. Even exposure to another crime-scene investigator who is wearing latex can cause an allergic response in
those allergic to latex.
Nitrile gloves are better than latex gloves and provide more protection. These gloves are inexpensive and resistant to
some chemicals. Neoprene gloves are chemical resistant and must be worn when processing scenes with chemicals,
such as acids and alcohol. At the crime scene, gloves should be changed often, and all contaminated protective gear
should be removed and disposed of in biohazard bags.
By wearing shoe covers, the investigator will avoid creating new foot tracks at the crime scene. It should be a standard
rule for investigators reponding to crime scenes with a substantial amount of blood or biological fluids to wear foot
protection, such as shoe covers or booties. The different types of foot protection include disposable Tyvek shoe covers
with vinyl soles, disposable Tyvek high-top boots with vinyl soles, and disposable rubber shoe covers. Tyvek shoe
covers are made to be strong and tear resistant. However, rubber shoe covers would be necessary at chemical crime
scenes, such as clandestine labs. The benefits of rubber shoe covers are that they won’t conduct electricity and are
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excellent to wear in wet environments. Alternatively, an investigator or technician can purchase and wear inexpensive
new shoes and dispose of the contaminated shoes after processing the crime scene.
An investigator may expose children and pets to diseases by walking in biological fluids at a crime scene and then
walking around in his or her residence with the same contaminated shoes. A crime-scene worker must have personal
rules such as always leaving work shoes at the front door of his or her residence. If you set personal rules from the
beginning, you can prevent contaminates from coming home with you. All nondisposable items such as lab coats,
towels, and personal clothing that may be contaminated with potentially infectious material should be placed in a
yellow plastic bag labeled “Infectious Linen” and laundered, at the expense of the employer, by a qualified laundry
service. Personal clothing that may have been contaminated should never be taken home for cleaning. If a qualified
laundry service for “Infectious Linen” is not available to the agency, these nondisposable items should be placed in a
red plastic bag and labeled “Biohazard Material.” These items will need to be destroyed because they may contain
infectious material.
BIOLOGICAL HAZARDS
UNIVERSAL PRECAUTIONS AND BLOODBORNE PATHOGENS
It is extremely important for every crime-scene technician to comprehend and apply the Universal Precaution Rule,
which states that when an individual responds to a crime scene that has blood or tissue, he or she must assume the
blood or tissue sample is infected and treat the sample as if it contains an infectious disease such as hepatitis B,
hepatitis C, human immunodeficiency virus (HIV), or any number of other infectious agents. Make sure you wear your
appropriate PPE, such as a mask and gloves, when working at a bloody crime scene or one involving biological fluids
or tissue.
In general, all of the infectious viruses (hepatitis B, hepatitis C, and HIV) are composed of either DNA or RNA viruses
that have the ability to infect humans by a number of different exposure routes. Whether the exposure is by an
accidental stick from a needle or knife or broken glass or some other hazard at the crime scene or the laboratory, there
is the possibility of acquiring an infection. Even indirect exposures caused by sloppy techniques such as talking on a
cell phone while working in the hot zone may introduce the virus to the mucus membranes of your mouth or eyes. To
prevent possible health hazards, a clean mask and gloves should be worn in the event a cell phone must be used at the
scene.
It is not uncommon for both hepatic viruses to be present in a contaminating source, along with the HIV virus. There
are numerous stages and clinical presentations that an individual with hepatitis can exhibit, and the ultimate outcome
of hepatitis is quite variable and beyond the scope of this chapter. It is important to remember that the best treatment
regarding exposure to blood-borne pathogens is prevention. Every crime scene technician should be vaccinated for
hepatitis to avoid contracting these diseases in the event of an accidental exposure. The hepatitis immunization consists
of three shots over a nine- to twelve-month period and should be effective for fifteen to twenty years.
In general, not every exposure to infected blood or bodily fluid will result in your acquiring an infection and the
disease. Numerous factors, including the viral load of the infected material or fluid, the promptness and thoroughness
of cleaning the site of the exposure (cuts or scraps or splashes), the route of exposure, and the immune system of the
exposed individual, all play a vital role in whether or not one will become infected.
If a piece of physical evidence is wet from blood, place the piece of evidence in a paper bag—even consider double-
bagging the item with two brown paper bags to keep the outside bag free of contamination—and then place it in a red
biohazard bag for transportation to the crime lab. Then, you can use the appropriate drying cabinet to let your evidence
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air dry before putting it in the property room. Remember to place a piece of butcher paper on the bottom of the drying
cabinet in case any evidence falls off the item onto the butcher paper during the drying process. The original paper bag
and the butcher paper should be kept and stored for possible analysis. After the contaminated bloody evidence has
completely dried, use butcher paper to fold the item to avoid creating new patterns on the item, then place it in a new
paper bag. Always remember to place a red biohazard sticker both on the final, secured evidence bag and the property
receipt to ensure all handlers will know the item is contaminated with biological fluids.
DIFFERENT TYPES OF EXPOSURE AT CRIME SCENES
When an investigator responds to a crime scene, there are several different ways in which he or she can be exposed to
toxins. If crime-scene personnel are trained and educated to identify these means of exposure, they can protect
themselves with the proper personal protection equipment. Among the contaminants that can be present at a crime
scene are various chemicals, gas, fumes, dust, and powders, and the only way to avoid exposure is by using the proper
PPE.
ABSORPTION
Absorption occurs when contaminants make contact with skin or absorb through mucus membrane areas, such as
nostrils, mouth, and eyes. Also, contaminants can absorb readily through an unprotected cut on the skin, which is an
easy point of entry. If contaminants come into contact with your eyes, rinse your eyes with water for a minimum of
fifteen minutes. Portable eyewash stations should be part of the crime-scene safety equipment.
INGESTION
Ingestion occurs when contaminants enter the body through the mouth. An individual must be careful when
considering drinking or eating at a crime scene to prevent ingestion of chemicals. The “cold zone,” a work area
described in detail in the following section, should be the only area within the crime scene where drinking and eating
take place. Chewing gum is another way to ingest such toxins at the crime scene and should be considered taboo.
INHALATION
Inhalation occurs when contaminants enter the body through the respiratory system. When an investigator or
technician responds to a crime scene, he or she must assess the scene to determine which respiratory mask will offer
the best protection from the contaminants present.
INJECTION
An injection can enter the body in the form of a needle or sharp object. When working with needles or sharp objects,
such as pieces of glass, an individual should wear proper gloves for protection and use special care to prevent being
poked by sharp objects. Crime-scene personnel should take their time to be safe when processing all sharp objects,
especially needles. They must also be mindful of how they package such objects for others who will receive the
evidence and may not know of the inherent risks of handling it.
WORK ZONES
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The “hot zone” is the active crime-scene area, which means contaminates and probable evidence exists in this region.
In the hot zone, all crime-scene technicians should be suited up with PPE, such as masks, foot protection, eye
protection, and gloves. There should be no food or drinks allowed in the hot zone. Also, the employees who are
actively working the crime scene should be the only ones allowed in this area. The warm zone is the transition area
between the cold and hot zones. This is the area where the crime-scene technicians will suit up with their PPE, and it is
the staging area for the equipment. After the crime-scene processing is complete, the warm zone should also be the
decontamination area used to prevent spreading any contamination. When potentially infectious materials are present
at a crime scene, personnel should maintain a red biohazard plastic bag for the disposal of contaminated gloves,
clothing, masks, pencils, wrapping paper, and so on. On departure from the scene, the biohazard bag must be taped
shut and transported to an approved biohazardous waste pickup site. The cold zone is the safe area for all personnel
who were not actively processing the scene. The first officer on the scene should be using this area to write down the
names of the individuals entering and exiting the actual crime scene, or hot zone. The cold zone is also the area where
employees can take breaks, eat, and drink. Every crime-scene technician should understand the importance of
establishing and maintaining these separate work zones in scenes where contaminants are present. When traveling
from the hot zone to the cold zone, decontaminating in the warm zone is essential.
Not every crime scene requires that work zones be established for safety. Simple cases such as burglaries and car thefts
do not require zone assignments. Obviously, homicides and other crime scenes that contain bodily fluids and/or
contaminants do require the establishment of work zones. The normal precautions of wearing gloves and masks and
the like are more than sufficient for low-risk crime scenes. When responding to crime scenes that are contaminated,
personnel need to know which zones are active, such as hot zone, warm zone, and cold zone, and therefore these zones
need to be clearly delineated by the investigator so that personnel do not cross them in an unprotected state.
Quick Review
• Updates of current crime-scene safety regulations and education should be made annually by a designated
crime-scene safety coordinator. Health inspections should also be included in the job requirements of personnel
who operate certain safety equipment used at the crime scenes.
• Law enforcement officers and crime-scene technicians at a crime scene must use caution and protect
themselves at all times from contracting AIDS or hepatitis. Bodily fluids must always be treated as though they
were infectious.
• Crime-scene technicians most often use dust particle masks or N-95 masks at routine crime scenes. They are
considered the most common type of respiratory protection. These masks are considered to be disposable and
should be discarded after one use.
• It is recommended that personnel always wear doubled-up latex gloves and possibly wear chemical-resistant
clothing, Tyvek-type shoe covers, a particle mask/respirator, goggles, and possibly face shields when potentially
infectious material is present. Gloves should be changed often while processing the scene.
• When processing and collecting evidence at a crime scene, personnel should be alert to sharp objects, knives,
hypodermic syringes, razor blades, and similar items.
• Eating, drinking, smoking, eating, and chewing gum are prohibited at the immediate crime scene.
• The hot zone is the active crime-scene area, which means contaminates and probable evidence exists in this
region. In the hot zone, all crime-scene technicians or investigators should be suited up with personal protection
equipment, also known as PPE, such as masks, foot protection, eye protection, and gloves. No food or drinks
should be allowed in the hot zone.
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