1. Lesson 04: Physical Evidence
(Chapter 5 of Bennett and Hess text)
2. Categories of Evidence
n
Testimonial---obtained
by interviewing and interrogating individuals about what they saw
n
Documentary---includes
written material, audio recordings, videos
n
Demonstrative---mock-ups,
scale models, visuals
n
Physical evidence---“real”
evidence that can be touched, seen, smelled, or tasted
3. Other Classifications of Evidence
n Evidence can be classified as either direct or indirect…
n Direct: establishes proof of a fact without the use of any other evidence (e.g., eyewitness testimony)
n Indirect/Circumstantial: evidence that may tend to incriminate a person, but is not direct proof (e.g., a footprint found at a crime scene)
4. Other Categories of Evidence
n
Corpus delicti evidence: Evidence that shows a crime
was committed (proves the elements or “body” of a crime)
n
Associative
evidence: Evidence that links (associates) a person to a crime
n
Trace evidence:
Extremely small evidence, such as fibers and hair, that often requires microscopic analysis
n
Prima facia evidence: Evidence established by law
n
Opinion evidence:
Evidence presented by an expert (e.g., forensic expert that a suspect’s DNA matches that found at a crime scene)
n
Hearsay evidence:
Evidence relayed by a third party that is not generally admissible in the prosecution’s case-in-chief
5. Prima Facie Evidence Example
KRS 514.110 Receiving stolen property.
(1) A person is guilty of receiving stolen
property when he receives, retains, or disposes of movable property of another knowing that it has been stolen, or having
reason to believe that it has been stolen, unless the property is received, retained, or disposed of with intent to restore
it to the owner.
(2) The possession by any person of any
recently stolen movable property shall be prima facie evidence that such person knew such property was stolen.
6. Opinion/Expert Testimony
n
Frye (Frye v. United States, 1923) standard:
The opinion must be based on sufficiently established principles that have “gained general acceptance in the particular
field in which it belongs”
n
Daubert (Daubert v. Merrell Dow Pharmaceuticals,
1993) standard:
n Replaced
the Frye standard
n Established a two-prong process that an expert’s testimony must be both reliable and relevant
7. Other Important Terms
n
Probative Evidence:
Evidence that tends to prove guilt or innocence in a case
n
Material evidence:
Evidence that forms a substantive part of a case and has effective influence on the outcome
n
Relevant evidence:
Evidence that applies to a matter in question
n
Competent Evidence:
Evidence that is properly collected and processed and is, therefore, admissible in court
n
Exculpatory
evidence: Evidence that tends to show a suspect’s innocence
8. Due Process
n Due
process means fundamental fairness
n Due
process is a constitutional right
n A
person cannot receive due process if altered, contaminated, or otherwise incompetent evidence is used against him/her in court!!
9. Integrity of Evidence
n
Competent evidence
is ensured, in part, by maintaining its integrity and making sure cross contamination does not occur
n Cross-contamination
can occur when items of evidence accidentally touch each other and exchange matter
n Maintaining
the integrity of evidence is making sure that it is in the same condition when introduced into court as when initially collected
n Chain
of evidence/custody is required to maintain the integrity of the evidence
10. Chain of Custody
n The
chain of custody is the documented control of evidence showing who maintained the evidence, where it was maintained, and what,
if any, changes were made to the evidence
n Also
known as the chain of evidence and chain of possession of evidence
11. Evidence should be documented with:
n
Name or initials
n
Address or general
location
n
Specific location
from which evidence was seized or collected (e.g., from rearview mirror)
n
Date/time collected
n
Description
(size, condition, amount)
n
Case or other
documenting number
n
Victim
n
Type of Offense
n
Witness to collection
12. General Evidence Collection Rules
n
Collect evidence
legally
n
Plan and collect
in a systematic and thorough manner
n
Collect safely
n
Document and
mark all evidence
n
Photograph,
measure, sketch as you search
n
Maintain chain
of custody
n
Store in secure
place with restricted access
13. Common mistakes when collecting evidence…
n Not collecting enough of the sample
n Not obtaining standards of comparison
n Not maintaining the integrity of the evidence
14. Guidelines for Preserving and Packaging Evidence
n
Handle evidence
in a way that prevents any change from occurring from time of collection until time received by lab.
n Place blood and other biological evidence in paper containers to prevent the accumulation of moisture that
may result in the sample mildewing.
n
Best if evidence
is submitted intact. Therefore, may need to submit item on which evidence is attached.
n
Each item of
evidence should be packaged separately to prevent cross contamination.
n
Air-dry all
items before packaging (except evidence related to arson in which there is a need to check for accelerants).
15. To satisfy court admissibility standards, investigators must be able to:
n
Identify each
item of evidence they collected or handled
n
Describe the
location and condition of the evidence at the time it was collected
n
State who/when
had contact with and/or handled evidence
n
Explain why
evidence was handled
n
Explain what
changes, if any, were made to the evidence
16. Class vs. Individual Characteristics of Evidence
n
Class Characteristics:
Characteristics of physical evidence that are common to a group of objects or persons (class).
n Regardless
of how thoroughly examined, such evidence can be placed only into a broad category (class); an individual identification cannot
be made because there is a possibility of more than one source for the evidence.
n
Individual Characteristics:
Evidence with individual characteristics can be identified as originating from a particular person or source.
17. Examples of Evidence with Class Characteristics
n Paint
n Safe
insulation
n Soil
n Hair
w/o skin cells attached
n Fibers
n Glass
fragments too small to match broken edges
18. Examples of Evidence with Individual Characteristics
n
Fingerprints
n
Handwriting
n
Firearms and
bullets
n
Tool marks
n
Shoeprints
n
Glass fragments
where edges may be matched
n
Hair with skin
cells attached (for DNA analysis)
n
Blood (DNA)
19. Soil and Pollen
n
Soil examinations
can determine whether soils share a common origin by comparing color, texture, and composition.
n
Soil and pollen
are class-characteristic evidence useful for:
Ø Helping to narrow or focus an investigation
Ø Determining the credibility of an alibi or defense
20. Soil Collection Guidelines
n
Collect as soon
as possible (due to changing conditions)
n
Collect from
scene and point of assess and escape
n
Multiple control
samples must be collected at the scene and within a 100 yard radius to test for variability
n
Lumps of soil
should be collected and preserved intact. (Because of layering.)
n
Collect form
areas of apparent change
n
Collect from
depths consistent with scene
n
Collect from
alibi areas
n
Use a map to
document collection locations
n
Allow forensic
experts to remove soil from clothing, shoes, etc. Collect the object the soil is adhering to on a suspect, wrap in paper,
and send to lab.
n
Air dry samples
and package in paper
n
Avoid cross
contamination- submit known and unknown samples separately in leak proof containers
21. Shoe/Tire Prints and Impressions
n
Prints- formed
when an item transfers foreign matter, such as blood, from one location to another
n
Impressions-
formed when an item is pressed into a moldable material, such a earth, clay, or snow
n
Evidentiary
value- Shoe and tire prints and impressions may have individual or class characteristics, depending on the quality and nature
of the samples.
22. Preserving and Collecting Prints and Impressions
n
Take “overall”
photograph
n
Take photographs
directly above with and without a scale
n
Collect item
on which print is located (if possible)
n
Use dental stone
to develop a cast
n
Never “fit”
an object onto a print or into an impression to see if they “fit”.
23. Paint
Evidentiary value of paint:
n
Absent paint
chips that can be individualized to a particular source, paint has class characteristics.
24. Collection of Paint Evidence
n
Collect paint
chips so as to keep chips intact.
n
Scoop up with
paper or pick up with tweezers.
n
Place in druggist
folds and glass or plastic vials.
n
Collect entire
garment if paint is embedded.
n
Obtain uncontaminated
control paint (known) for comparison.
n
Collect control
paint as close as possible to area of impact.
n
Collect all
paint layers. 1/4 inch square samples are sufficient.
n
Use clean scalpel
or knife.
n
Collect samples
separately and with clean or different instruments to avoid cross transfer.
n
Package individually.
n
Collect items
containing paint (tools) rather than remove paint.
n
Do not collect
paint from impressions made by tools.
25. Glass
Evidentiary value of glass:
n
Individual characteristics.
n
Class characteristics.
Most glass submitted to the lab is too fragmentary or small to permit examining for individual characteristics. This glass
can be characterized by density and refractive index.
26. Glass May Reveal…
n The examination of a bullet hole can reveal the direction of the bullet.
n The
hole will be wider at the point of exit.
27. Glass May Reveal…
n
The examination
of stress marks can reveal the direction of force used to break the glass.
n
On a radial
crack, the surface with the perpendicular lines is the opposite side on which the force is directed.
n
The 3R rule:
Radial cracks form a Right angle on the Reverse side of the force.
28. Glass May Reveal…
n
The sequence
of penetrations.
n
A fracture always
terminates at an existing line of fracture.
29. Collection of Glass Evidence
n Tape
should not be used to collect glass evidence and any processing for latent prints is ordinarily done in the laboratory.
n Collection
must be thorough- attempt to collect all the fragments.
n Package
in containers to prevent further breakage.
n Collect
control from scene to compare with suspect glass.
30. Fibers, Cloth Fragments, and Impressions
n
Evidentiary
value of fibers: Unless a torn fabric or fragment can be fitted with another along its edge, most fibers will yield class
characteristics. Identifying features of fibers:
Ø Color
Ø Diameter
Ø Morphological features such as striations or pitting
Ø Cross-sectional shape
Ø Chemical composition (places it in a class such as nylon)
31. Collection of Cloth and Fiber Evidence
n
Generally involves
the collection of potential "carriers".
n
Clothing should
be carefully folded and placed in paper bags.
n
Articles should
be packaged separately to prevent cross contamination.
n
Adhesive lifts
of a body thought to have been wrapped in a blanket or rug might yield fibers.
n
Fibers observed
should be removed immediately with clean forceps and placed in paper envelops or pill boxes
32. Fingerprints
n
Visible- ridges
are contaminated with foreign matter and transferred to an object (e.g., blood, oil, ink).
n
Plastic (e.g.,
prints made in wax, putty, and butter and are analogous to impressions).
n
Latent (invisible).
33. Locating Fingerprints
n
Recreate suspects’
movements through witnesses and common sense.
n
Use strong flashlight
at oblique and varying angles.
n
Be thorough
and have patience and perseverance.
34. Developing Fingerprints
Most commonly used methods of processing
fingerprints:
n
Powders
n
Chemical: Iodine
fuming, Ninhydrin, Silver nitrate, Super glue
35. Preservation of Fingerprints
n
Photography:
Any close up shot with a camera or a special camera allowing 1:1 photograph
n
Lifting
n
Documentation
(i.e., in notes, reports, and on each individual lift)
36. Dental Evidence
n
Dental Identification
n
Bite- Mark Evidence
37. Collection of Bite Mark Evidence
Victim
n
Photograph overall
area (victim, object, location, etc.)
n
Photograph bite
mark using a scale
n
Medical personnel
should swab bite-marks for laboratory analysis of saliva or blood
n
Photograph again
after swabbing and after 12-24 hours or several days later
Suspect
n
Obtain records,
impressions, saliva and blood sample
n
Do so in timely
manner as teeth can be altered by a suspect. It is best not to inform a suspect in advance or publicize the existence of bite-mark
evidence
n
Obtaining a
search warrant or court order may be best in order to reduce risk of a suspect altering teeth
38. Hair
n
Evidentiary
value of hair: Hair is most frequently found at the scene of violent crimes. Generally,
hair has class characteristics. However, if the root is attached and nuclear DNA can be extracted, hair may have individual
characteristics.
39. Analysis of Hair May Reveal…
n
Whether hair
is human or animal
n
Species
n
Whether hair
was dyed or bleached
n
Difference in
shampoo residues
n
The presence
of contaminants, such as gunshot residues, blood, and semen
n
Morphological
abnormalities such as disease or deficiencies
n
Whether hair
is Caucasoid, Negroid, and Mongoloid
n
Body area from
which hair originated
n
Whether hair
was forcibly removed (Follicular tissue attached may indicate forcibly removed.)
n
Drug use and
how long ago they were taken
n
Whether a person
is a smoker or non-smoker
n
Whether questioned
hair compares with known hair
40. Collection of Hair Evidence
n
Collect adequate
number from victim and all persons suspected of having deposited hair at the scene
n
Collect hair
from pertinent body areas
n
For known samples,
collect 50 full length hairs from different areas of the scalp and two dozen full length pubic hairs from generalized or representative
areas
n
In rape cases,
the pubic areas should be combed to obtain foreign hair. Also package the comb.
n
Pulled hair
is preferred since full length is needed.
n
Collect hair
from victim at autopsy even though the need may not be apparent.
41. Blood
n
Evidentiary
value of blood: Blood is commonly located at crime scenes, especially violent crime scenes. Blood may yield individual characteristics
during DNA analysis.
42. Analysis of Blood May Reveal…
n
Is it blood?
n
Species
n
Sex
n
Blood type
n
Drugs or alcohol
used
n
Presence of
certain types of venereal diseases
n
Presence of
carbon monoxide
n
Whether the
source was a smoker
43. Analysis of Bloodstains May Reveal…
n
Direction of
blood droplets
n
Distance from
source to surface where droplets are found
n
Angle of droplet
impact
n
Direction and
relative speed of blood trails
n
Nature of weapon
n
Number of blows
n
Relative locations
of other persons, surfaces, objects that have droplets
n
Sequence of
events
44. Interpretation of Patterns
n
A stain originating
from a right angle to a surface produces a circular stain. As the angle of impact increases, the stain becomes elongated in
shape.
n
The pointed
end of a stain always faces its direction of travel.
45. Interpretation of Patterns
n The origin of several splatters can be determined by drawing a straight line through the long axis of several
of the stains.
46. Preservation of Blood Evidence
n
Record through
photography, notes, and sketches.
n
Collect all
clothing from victim and suspect, even if no blood is visible
n
Collect wet
blood with a dropper, if possible
n
If not, allow
to dry and then package in a paper bag or well-ventilated box
n
Do not package
blood evidence in plastic or airtight containers
n
Swab or collect
controls (To show that test results are the result of the blood present and not the material on which the stain is located.)
n
Collect entire
item stain is on
n
If this is not
possible, use clean scalpel and scrap blood onto clean paper
47. Firearms
n Bullets and cartridge cases may be individualized or related to single source because of peculiar scratches,
nicks, breaks, and wear they received during manufacturing or afterwards during their use.
48. Examination May Reveal…
n
Does the firearm
function properly?
n
Make, caliber,
type of bullet?
n
Possible firearm
type from which a bullet is fired?
n
Was a particular
bullet fired from a particular firearm?
n
Was a particular
cartridge case extracted from a particular firearm?
n
Size, gauge,
manufacturer of shot and wadding?
49. Gunshot Residue
n May reveal if a subject fired a weapon
50. Gunshot Residue
n May reveal muzzle to target distance
51. Collection and Preservation of Firearms Evidence
n
Photograph all
evidence prior to moving it
n
Place all ammunition
in separate boxes
n
When checking
weapons for prints, include the magazine and individual shell casings
n
Either mark
the firearm evidence for identification, or place each item in a separate container and mark and seal the container
n
Wrap projectiles
in tissue and place them in a pillbox or similar container
n
Document the
exact location of ejected casings from a semi-automatic.
n
Collect all
wading and pellets located from a shotgun blast.
n
Do not cut clothing
from victim near the area of bullet holes.
n
Air-dry all
clothing.
n
When packaging
clothing, do not fold in the area of the bullet hole
52. Tool Mark Evidence
Evidentiary value:
n
Most often reveals
class characteristics such as shape and size
n
Occasionally
reveals individual characteristics through an examination of striations and minute imperfections
n
Tools may yield
foreign deposits such as paint, blood, metal
53. Collection and Preservation of Tool Marks
n
Photograph
n
Collect the
entire object containing the tool mark, if practical.
n
Use casting
material (silicon or dental plaster) to obtain a cast.
n
Do not “fit”
the tool into the mark to see if it fits.
n
Place suspected
tools and tool mark evidence in separate containers.
n
Be careful not
to destroy or disturb possible trace evidence such as paint.
54. Be Determined…
The collection
of evidence is a tedious process. Take your time. Remember your goal- justice through due process and the integrity of the
evidence.
55. Sources
Bennett, Wayne and Karen Hess, Criminal
Investigation, Sixth Edition, Belmont, CA: Thompson Learning, 2001.
Bennett, Wayne and Karen Hess, Criminal
Investigation, Eighth Edition, Belmont, CA: Thompson Learning, 2007.
Fisher, Barry, et. al., Techniques of
Crime Scene Investigation, Fourth Edition, New York, NY: Elsevier, 1987
Saferstein, Richard, Criminalistics,
Seventh Edition, Upper Saddle River, NJ: Prentice Hall, 2001.
Saferstein, Richard, Forensic Science
Handbook, Volume I, Upper Saddle River, NJ: Prentice Hall, 2002.
Swanson, Charles, et. al., Criminal
Investigation, Eighth Edition, Boston, MA: McGraw-Hill, 2003.
