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.

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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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