Types of Evidence

Classification of Evidence
Testimonial evidence is a statement made under oath;
also known as direct evidence or prima facie evidence.

Physical evidence is any object or material that is relevant in a

crime; also known as indirect evidence. Examples are hair, fiber,
fingerprints, documents, blood, soil, drugs, toolmarks, impressions,
glass.

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 Types of Evidence

Reliability of Eyewitness
Factors that affect accuracy:
Nature of the offense and the situation in which
the crime is observed
Characteristics of the witness
Manner in which the information is retrieved

Additional factors:
Witness’s prior relationship with the accused
Length of time between the offense and the
identification
Any prior identification or failure to identify the
defendant
Any prior identification of a person other than the
defendant by the eyewitness

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 Types of Evidence

Eyewitness
A police composite may be
developed from the
witness testimony by a
computer program or
forensic artist.

FACES—a composite
program by InterQuest
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 Types of Evidence

As a result of the influences on

Physical Evidence eyewitness memory, physical evidence
becomes critical.

Is generally more reliable than testimonial evidence

Can prove that a crime has been committed

Can corroborate or refute testimony

Can link a suspect with a victim or with a crime scene

Can establish the identity of persons associated with a crime

Can allow reconstruction of events of a crime

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 Types of Evidence

Reconstruction
Physical evidence can be used to
answer questions about:
What took place at a crime scene
The number of people involved
The sequence of events

A forensic scientist compares the questioned or unknown sample from

the crime scene with a sample of known origin.

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 Types of Evidence

Types of Physical Evidence

Transient evidence is temporary; easily changed or lost; usually observed by
the first officer at the scene.
Pattern evidence is produced by direct contact between a person and an object
or between two objects.
Conditional evidence is produced by a specific event or action; important in
crime scene reconstruction and in determining the set of circumstances or
sequence within a particular event.
Transfer evidence is produced by contact between person(s) and object(s), or
between person(s) and person(s).
Associative evidence is something that may associate a victim or suspect with
a scene or with each other; e.g., personal belongings.

—Henry C. Lee and Jerry Labriola, Famous Crimes Revisited, 2001

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 Types of Evidence

Examples of Transient Evidence

Odor—putrefaction, perfume, gasoline,
urine, burning, explosives, cigarette or
cigar smoke
Temperature—surroundings, car hood,
coffee, water in a bathtub, cadaver
Imprints and indentations— footprints,
teeth marks in perishable foods, tire
marks on certain surfaces

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 Types of Evidence

Examples of Pattern Evidence

Pattern evidence—mostly in the form of imprints, indentations,
striations, markings, fractures, or deposits

Blood spatter Clothing or article distribution

Glass fracture Gunpowder residue
Fire burn pattern Material damage
Furniture position Body position
Projectile trajectory Toolmarks
Tire marks or skid marks Modus operandi

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 Types of Evidence

Examples of Conditional Evidence

Light—headlight, lighting conditions, Vehicles—doors locked or unlocked,
lights on or off windows opened or closed, radio off
or on, odometer mileage
Smoke—color, direction of travel,
density, odor Body—position and types of wounds;
rigor, livor, and algor mortis
Fire—color and direction of the flames,
speed of spread, temperature and Scene—condition of furniture, doors
condition of fire and windows, any disturbance or
signs of a struggle
Location—of injuries or wounds, of
bloodstains, of the victim’s vehicle, of
weapons or cartridge cases, of
broken glass

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 Types of Evidence

Classification of Evidence by Nature

Biological—blood, semen, saliva, sweat, tears, hair, bone, tissues, urine, feces,
animal material, insects, bacteria, fungi, botanical material

Chemical—fibers, glass, soil, gunpowder, metals, minerals, narcotics, drugs,

paper, ink, cosmetics, paint, plastic, lubricants, fertilizer

Physical—fingerprints, footprints, shoeprints, handwriting, firearms, tire marks,

toolmarks, typewriting

Miscellaneous—laundry marks, voice analysis, polygraph, photography, stress

evaluation, psycholinguistic analysis, vehicle identification

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 Types of Evidence

Evidence Characteristics
Individual—can be identified with a particular person or a single source
•Fingerprints - 1 X 1060
• 1 in 1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000

Fingerprints Blood DNA Typing

Class—common to a group of objects or persons

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 Types of Evidence

Class vs. Individual Evidence

These fibers are class evidence;
there is no way to determine if
they came from this garment.

The large piece of glass fits exactly

to the bottle; it is individual
evidence.

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 Types of Evidence

Class vs. Individual Evidence, continued

Which examples do you think could be

individual evidence?

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 Types of Evidence

Forensic Investigations
Include some or all of these seven major activities:
1. Recognition—the ability to distinguish important evidence
from unrelated material
Pattern recognition
Physical property observation
Information analysis
Field testing

2. Preservation through the collection and proper packaging of

evidence

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 Types of Evidence

Forensic Investigations, continued

3. Identification using scientific testing
Physical properties
Chemical properties
Morphological (structural) properties
Biological properties
Immunological properties

4. Comparison of class characteristics measured against those of

known standards or controls; if all measurements are equal, then
the two samples may be considered to have come from the same
source or origin

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 Types of Evidence

Forensic Investigations, continued

5. Individualization in demonstrating that the sample is unique, even

among members of the same class

6. Interpretation—giving meaning to all the information

7. Reconstruction of the events in the case

Inductive and deductive logic
Statistical data
Pattern analysis
Results of laboratory analysis
—Henry C. Lee and Jerry Labriola, Famous Crimes Revisited, 2001

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Collecting Trace Evidence
Who collects the evidence?
 Police Officer
 Crime Scene Investigator
 Forensic Scientist

Depends on the state/community

Often one person to ensure consistency
of labeling
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Trace > Collecting

Collect trace or entire object?

Suppose a glove appears to have

glass, fibers and blood on it.
Should the glass, fibers and
blood be removed and
packaged separately?

Should the entire glove be packaged?

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Trace > Collection

Considerations before packaging entire object:

 Object may be too large or difficult to move

 Trace evidence may fall off item during transport.
 Trace Evidence may be transferred to different,
irrelevant area of object.

If packaging object, package objects separately.

Prevents trace being transferred to other objects.

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Trace > Collection

These 3 methods can be done at the

crime scene or in the crime lab.

1. Visual Inspection
2. Tape Lift
3. Vacuum

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Trace > Collection

Visible Inspection
 Use naked eye or hand lens.
 Evidence removed and packaged for later
analysis
 Use bright light and forceps to collect.

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Trace > Collection

Visible Inspection (Packaging)

 Small paper envelopes are bad (Holes

allow small objects to escape).
 Use small plastic bags, glass vial or paper
using a druggist fold.
 Double package. Label each package.

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Trace > Collection

Tape Lift
 Clear tape is used.
 Repeatedly apply tape to small area until
most of the stickiness is gone.
 Tape is folded back upon itself, taped to a
glass slide or taped to a piece of plastic.
 Put in separate labeled container.
Be sure to document specific area covered.

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Trace > Collection

Vacuuming

 Nozzle should be
short and
transparent.
 Debris is collected
on a filter or
membrane

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Trace > Collection

Vacuuming
 Small area is vacuumed. (Filters changed
frequently)
 Filters packaged in separate labeled
container. (Be sure to document specific area
covered)
 Most improperly used method because it
often results in the collection of a lot of
irrelevant material.
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Druggist Fold
 Consists of folding one end of the paper
over one third, then folding the other end
one third over that, and repeating the
process from the other two sides.
 After the paper is folded in this manner,
the outside two edges are tucked into
each other to produce a closed container
that keeps specimen from falling out.

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 Types of Evidence
Wayne Williams Trial

• Fulton County Case in 1981

• First case in which primary evidence was
fiber evidence
• Fibers linked Williams to being in contact
with the bodies
• Media released info that GBI/FBI were
collecting fibers
• Williams began dumping nude bodies in
rivers
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 Types of Evidence
Wayne Williams Trial

• Fiber links to dog, cars, home, bedspread

• He was convicted for being linked to the
bodies prior to dumping
• Set standard for murder trials based on
overwhelming circumstantial evidence

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