Powerpoint Presentation

1. Trace Evidence – any material or article found to recovered during
the crime scene investigation which may assist in the solution of a case
and the prosecution of the guilty.
One of the most common types of physical evidence that an investigator
and/or crime scene specialist will encounter will be trace evidence. Trace
evidence is a generic term for small, often microscopic material. Trace
evidence at a crime scene can include such obvious things as blood, hair,
glass particles, or paint. This can also include less obvious items such as
minute fibers or even soil. Therefore we are going to discuss the general
properties of hair, fibers, glass, paint and soil and look at the value of
each as evidence, and how to collect each of them properly.
TRACE EVIDENCE

3. I. Hair
• Hair is one of the most common types of trace
evidence found at a crime scene. Next to teeth and
bones, it is also one of the most decay- resistant human
elements.
•
Structure of Hair
Structurally, a hair is composed of the tip end,
cuticle cortex, medulla, and bulb or root.
1. Cuticle – is the outer surface of the hair and when
viewed under a microscope appears composed of a
scale-like flakes, each overlapping the other similar to
the overlapping of singles on a roof or scales on a fish.
These scales are known as cuticular scales.

4. 2. Cortex – The cortex is the inner portion
of the hair and contains the pigmentation or
coloring of the hair.
3. Medulla – Is the core or center portion of
the hair shaft and when magnified, appears
as irregular, spinal, chain, or a continuous
dark line of varying width, running up the
center of the hair shaft.

5. Hair Evidence

6. VALUE OF HAIR AS EVIDENCE
The value of hair as evidence in criminal cases has
been clearly recognized. Hair is seldom conclusive
as evidence, but in conjunction with other details,
has proven to be an important and essential aid to
the investigator. The investigator and crime scene
specialist must specialize on the importance of this
type of evidence during the initial phase of the
investigation

7. • The origin and texture of hair found at a crime
scene, on a body, clothing, or headgear of a
suspect or victim may be exceedingly important
as evidence, particularly in homicides and sex
crime. Hair may be pulled out during the crime
and found at the scene or on the victim. Hair may
be pulled out during any physical contact
between the suspect and the victim. Hair may fall
out under conditions that the suspect is not
aware of and unable to guard against. Properly
handled by the crime scene specialist and
investigator, hair may provide excellent
investigative leads and add to the evidentiary
facts being assembled.

8. SEARCH, COLLECTION AS AN EVIDENCE AND
OBTAINING HAIR STANDARD
• The most difficult task facing crime scene specialist
is to initially locate hair evidence at the crime scene.
The search of the crime scene must be thorough,
detailed and exact. Obvious locations to search
include headgear and clothing, with special attention
given to linings, pockets and cuffs. In addition to the
general crime scene area, other areas to search may
include the victim’s body (especially in sex crimes),
underneath the fingernails, and any upholstered
surfaces such as furniture or car seats.
SEARCHING FOR HAIR

9. COLLECTION OF HAIR AS EVIDENCE
• Hair discovered at the crime scene should be
carefully removed with a pair of tweezers. The hair
sample should be placed in a clean container, such
as a pill box, or it may be folded into a piece of clean
paper. If a pill box is used, the crime scene specialist
should ensure that the entire length of the hair is in
the box and it is not crushed when the lid is put on. If
paper is used, special care should be taken to avoid
kinking the hair by folding.
• After collecting all visible items of evidence at the
crime scene, the premises are swept with a vacuum
sweeper that has a filter attachment. The contents of
the vacuum will then be placed in plastic bags and
properly labeled.

10. • Of paramount importance is avoiding contamination
of the evidence. Hair evidence is particularly
susceptible to cross contamination, and the crime
scene specialist must ensure that evidence gathered
from the suspect and from the victim is not
intermingled. Hair evidence must be individually
collected, properly packaged and labeled, and
properly separated during packing for transmittal.

11. OBTAINING HAIR STANDARDS
• Each hair found at the crime scene must be compared with a
standard sample obtained from all possible sources. Hair
standards should be taken from the victim and all possible
suspects. Standard head hair samples are taken from multiple
areas of the head (top, side and back) to ensure representative
shade and color range of the hair.
• When collecting hair standards from a live victim or suspect,
the head and pubic areas should first be combed before hair
samples are collected. Pulling is the recommended method for
collecting hair samples from all persons, living or dead. If for
some reason the hair samples are cut, the cut should be made
as close to the skin as possible. If pets or fur are involved in
the investigation, hair standards should also be obtained from
them.
• Hair standards and samples can be easily contaminated if the
crime scene specialist fails to use a new comb or fail to clean
the tweezers or scissors after each area is sampled

12. II. FIBERS
A fiber or filament is the smallest single
unit forming the basis of the textile yarn. A
yarn is composed of numerous fibers which
are spun, twisted, or drawn together to
prepare the unit for weaving or knitting. E
yarn is sometimes called a thread by the
layman.

13. • CLASSES OF FIBERS
Fibers may be divided into he following classes:
1. Animal – A number of fibers are derived from
animals, the most important being wool, silk,
camel’s hair, and fur.
2. Vegetable – this class includes cotton, linen,
jute, hemp, ramie, and sisal.
3. Mineral – minerals provide fibers such as
glass, wool, and asbestos.
4. Synthetics- Chemistry has produced a number
of fibers including rayon, nylon, orlon, and
Dacron.

14. SEARCHING FOR FIBER EVIDENCE
• The location and collection of fiber evidence at a
crime scene can be a difficult task. Due to their
minute size and composition, fibers must be sought
out in a through, detailed and exacting fashion. The
crime scene specialist should search clothing,
headgear, and pay particular attention to linings,
pockets, and cuffs. The general crime scene itself
should be carefully searched for all fiber evidence,
particularly any location that may have been the site
of a struggle or assault.

15. VALUE OF FIBERS AS EVIDENCE
• The value of fibers as evidence in criminal cases has
also been widely recognized. Fiber evidence is
seldom conclusive by itself, but in conjunction with
other details or evidence, it has often proven to be
an important and valuable aid to the crime scene
specialist. The crime scene specialist must make
every effort to maximize the possible use of fibers as
evidence during the investigation.

16. • Fiber evidence can help place a suspect at the scene
of a crime. Fibers may unwittingly be left at the crime
scene by the suspect. Later, a laboratory examiner
may determine that these fibers originated from an
article of clothing that was worn by the suspect,
which may have been described by the victim or
witnesses.
• Fiber evidence may also be interchanged between
the victim and the suspect, particularly during
crimes of violence such as rape, assault, or murder.
This interchange can also help prove that the
suspect and the victim were in each other’s
presence. Such convincing evidence can severely
attack the credibility of a rapist’s alibi, particularly
when it is claimed that the victim was never in his
presence.

17. COLLECTION OF FIBERS AS EVIDENCCE
• Fibers are primarily recovered from the sweepings of a crime
scene and the clothing of victims and suspects. Because fibers
are very easily transferred from garment to garment, proper
collection requires special care.
• In order for fiber examination to have maximum value in
associating the suspect with the victim or the crime scene,
standards of all materials which may have been contacted by
the suspect at the crime scene should be collected. Fiber
standards should be obtained from every possible source,
including clothing of both the victim and the suspect, rugs,
drapes, wall coverings, furniture, etc. If possible, the entire
object should be submitted. If this is not feasible, obtain a large
enough sample to ensure accurate comparison.

18. COLLECTING HAIR AND FIBER EVIDENCE FROM THE SUSPECT
• When a suspect is apprehended shortly after a crime
has been, particularly in the case of a rape or
sexxual assault, the suspect should be required to
undress while standing on a clean sheet of wrapping
paper. White is preferred, however, brown wrapping
paper is acceptable. The paper should be large
enough to catch any hairs or fibers that may drop
from the suspect as he/she undresses. All items of
clothing should be packaged separately, along with
the paper used during the process.

19. • When searching the suspect’s home and automobile,
do not overlook such items as combs, brushes, bed
linens, and dirty clothes in laundry baskets and
hampers. All of these are potential evidence
collection sites.
• Automobiles believed to be involved in hit and run
accidents should be carefully examined for the
presence of hair and fiber evidence. Bumpers, grills,
door handles, and chrome strips on the vehicle are
all prime locations for this type of evidence to be
deposited by the victim.

21. III. GLASS
• Glass - is normally a fused mixture of silica, usually in the form
of natural sand and two or more alkaline bases such as soda,
lime, or potash. Glass also contains quantities of various other
element and metals, present either as incidental impurities in
the basic ingredients, or added to them for color, degree of
hardness, heat-resistance, and other specific purposes.
• These ingredients are melted in a crucible under very high
temperatures, and the molten mass is then either rolled, blown,
or molded into desired sizes and shapes. It may later be
polished, ground, or cut for useful or decorative purposes, or it
may combined with other materials. For example, safety glass
is formed by fusing sheet vinyl plastic between sheets of plain
glass, and boron is added to provide greater resistance to
temperature (i.e. Pyrex glass)

22. VISUAL DISTINCTION OF GLASS
• When one looks at a piece of glass there are several
distinctions that can be readily observed with the
naked eye. These include:
• Color
• Thickness
• Curvature (if any)
• Surface Texture

23. • Glass is very unique, since there can be thousands
of different formulas in the making of glass. From
the simple pane glass to the wide variety of colored
glass, each has its own physical properties that
make it unique. For example, metals can be added to
make the various colors:
• 1. Iron = Greenish
• 2. Copper= Bluish
• 3. Manganese= Brownish
• 4. Gold= Ruby red

24. VALUE OF GLASS AS EVIDENCE
• Glass can have relatively high value as evidence
because of the identifiable variations in its physical
properties and methods of manufacture. The
evidence value of glass is also enhanced by the fact
that large fragments may frequently be physically
matched. Such physical matches are positive or
certain. However, a laboratory is limited in that it can
only conclude that particular glass evidence
consisting of tiny granules “has the same
composition” as the original glass. Unless a
fragment can be perfectly fit into an original glass
piece, a certain conclusion cannot be reached.

25. THE STRENGHT OF GLASS AND GLASS FRACTURES
• It is important to remember that the strength of
glass is in its surface. As soon as the surface is
penetrated or scratched, for example, using a
diamond tip pencil, glass will tend to break along
that scratch line. Once the surface is damaged, the
remainder of the material is easily cracked or
fragmented.
1. Glass always breaks under tension, not
compression. It will bend, until the tensile strength
is exceeded, and then break.
2. A focused impact upon glass will produce a
predictable pattern of fragmentation.
3. Radial fractures are primary fractures.
4. Spiral or concentric fractures are secondary
fractures.

26. • In the case of two or more focused impacts upon a
glass surface, the fragmentation pattern can help
determine which impact was made first. Succeeding
impact radial fractures will stop at the juncture of the
fractures produced by the first impact.
• Fracture patterns are unique and examination can
result in valuable information as to the direction of
breaking force. A physical match of two pieces of
glass results in an opinion that they came from a
common source to the exclusion of all other
sources.

27. COLLECTION OF GLASS AS EVIDENCE
• Where pieces are large enough to fit together, all
available glass must be submitted to increase the
probability of finding matching edges.
• Large fragments of glass must be placed in large
containers that will prevent further breakage.
• In cases where the direction of the breaking force is
required, pieces left undisturbed in the window must
be marked as to the inside, outside, top and bottom,
and all available glass must be submitted so that
enough pieces can be fitted together to identify the
radial cracks near the point of impact, and the point
of impact.

28. • Particles of broken glass from a hit-and-run vehicle
are often present on the victim’s clothing. Many
times, the driver of a hit-and-run vehicle will emerge
from the vehicle to determine what was hit, or how
seriously the victim was injured. Consequently,
broken glass from the accident may also be found
embedded in the driver’s shoes.
• A suspect’s clothing and shoes should be collected
in a similar manner to the collection of fiber evidence
that was previously discussed.
• Tools, shoes, and other evidence connected with the
suspect should be packaged separately and sealed.

29. Characteristics of Glass Evidence

30. Concentric fracture

31. Characteristics of Glass Evidence

32. Characteristics of Glass Evidence

33. GLASS FRACTURES:
Types of Fractures
A. Radial fracture – primary fracture resembles the wheel
radiating outward from the point of impact .
B. Concentric Fracture - secondary fracture having the
appearance of circles around the point the point of impact
connecting one radiating crack to the other, thus forming
triangular pieces of glass.
From the study of this two types of fractures it is possible
to derive the following:
a. POINT OF IMPACT – The front of the glass can be
determine due to the accumulation of dust and dirt on the
glass

34. b. DIRECTION OF IMPACT – a bullet will make a clear cut hole in the
side of entrance rather that on the exit side. If a shot is fired
perpendicularly it will give a crater of uniform flaking. If the shot is
fired at an angle from the right, the left exit side of the glass will give
more flaking and vice versa. Depression will be produced on the exit
side of the glass due to the rebound of the glass. Radial fracture can
be felt on the exit side and the concentric fracture on the entrance
side.
c. CAUSE OF FRACTURE – fracture due to heat does not exhibit a
definite pattern of radial and concentric fracture but are
characteristically wavy. The show very little stress lines whereas
fractures due to mechanical means show a definite pattern of radial
and concentric fractures.
DETERMINATION OF THE FIRST SHOT FROM A SERIES OF SHOTS:
The radial fracture of the first bullet hole will end stop the radial
fractures of the succeeding bullet holes.

36. Characteristics of Paint Evidence

37. Characteristics of Paint Evidence
Motorcycle & Car crash in Sweden

38. IV. PAINT
• When one thinks of paint, the first identifying
characteristics that comes to mind is usually color.
Color is determined by the use of various dyes or
granules of pigment in the paint. Aside from color,
paint also has a wide variety of other distinguishing
characteristics. These include its general
composition, i.e. oil-based, acrylic, water-based
(latex), etc., as well as its texture and finish, such as
flat, semi-gloss or gloss. All of these characteristics
combined create a very unique paint signature.

39. VALUE OF PAINT AS EVIDENCE
• As previously noted, paint can be very distinctive in its
characteristics. Likewise, paint, in any form, can be useful as
clue material in an investigation. Paint evidence may be in the
form of a chip from a dried paint surface, trace, smear, or intact
on some object. Paint as physical evidence is most frequently
involved in burglary and hit-and-run accident case.
• Whenever a suspect tries to force entry into a building, some
type of instrument is likely to be used. If the object being forced
is painted, chips of that paint may cling to the instrument being
used, and may also fall onto the suspect’s clothing. Also, if the
instrument being used is painted, some of the paint may be
transferred to the object being forced open. Transfers of paint
chips, or traces, are equally probable in automobile collisions.

40. COLLECTION OF PAINT AS EVIDENCE
• Paint as evidence may be collected in one of the
following forms:
 Small flakes or chips
 Traces of oxidized (chalking) paint.
 Smears from fresh paint
 An intact painted surface or item.

41. • Paint chips are usually the highest of evidentiary
value, primarily because they are more likely to be
overlooked by a suspect trying to rid his person or
possessions of traces that could link him to the
crime. However, regardless of its form, all paint
evidence generally has a high value in an
investigation.
• Paint chips are most likely to result from an attempt
to force something, or as a result of any violent
contact between objects (one of which has a painted
surface). Paint chips should be collected very
carefully to keep them intact. The larger the paint
chip, the higher its value as evidence. Chips may be
picked up with tweezers, but a preferable method is
to scoop them up with a clean piece of paper.

42. OBTAINING PAINT STANDARDS
• In order for a crime laboratory to make a comparison,
standards or samples of paint that have a known origin must be
taken. When samples are collected from any painted surface,
the paint should be chipped rather than scraped off. This will
prevent the layer structure from being altered and will prevent
the loss of important potential points of identification.
• The paint standards should be taken from two sources: one
from within any area damaged in the commission of a crime,
and the other from an adjacent undamaged area. An important
exception to this procedure is if the damaged area is a tool
mark, no paint sample is taken from within so that the mark
does not get altered. Only a sample from the adjacent
undamaged area should be taken.
• In hit-and-run investigations, it is important that the standards
from the undamaged painted area of an automobile be taken
from the areas immediately adjacent to the point or points of
impact, but not from an area in which the paint is corroded.
Each paint sample should be separately packaged and marked
to indicate the exact location of its recovery.

43. Soil samples in a lab

44. V. SOIL AND ROCKS
Soils and rocks vary in different locations throughout the world.
Differences can also be found within small local areas. The
differences between two types of soil, such as sand and clay, may
be easily recognized. However, detailed differences and similarities
between samples of similar soil or rocks can only be detected by
qualified laboratory chemists.
Value of Soil and Rocks as Evidence
Soils, rocks, and other minerals may be found:
1. On the suspect.
2. On the suspect’s shoes.
3. on the suspect’s clothing.
4. In the suspect’s vehicle.
5. On tools used in the crime.
6. At the scene of the crime.
7. On the victim.

45. These materials can provide valuable circumstantial
evidence. However, such evidence is often overlooked
because the investigator or crime scene specialist is neither
aware of its potential value nor of the laboratory services
available to make comparisons.
Soil cannot be positively identified as coming from one
source to the exclusion of all others, but the laboratory
expert can associate questioned soil with a most probable
source, conclude that a source cannot be eliminated, or that
a point or area could not be the source of the questioned
soil. These conclusions have proven extremely valuable in
providing criminal cases.

46. Searching for Soil and Rock Evidence:
Soil and rock evidence is more likely to be found when the
crime was committed outdoors or when the suspect walked
or drove a vehicle on unpaved ground. Clothing, shoes, and
other personal belongings that appear to contain soil, rock
particles, grime, dust, mud or the like, should be seized as
evidence and individually packaged.

47. Soil and rock evidence can be derived in the
following ways:
1. The suspect may carry and leave small amounts of rock
and soil at the crime scene.
2. The suspect may pick up soil and rock materials at the
crime scene.
3. The suspect may both leave and pick up soil and rock
evidence.
4. In a hit-and-run accident, the suspect or his vehicle may pick up
and leave soil and rock evidence. The impact of the collision
may dislodge dirt and mud that had accumulated on the
undercarriage of the suspect vehicle. Such particles can be
found on the road or on the body or clothing of the victim who
was struck by the vehicle. The suspect’s vehicle may also run
off the road, and in doing so, pick up mud and on its tires and
undercarriage that can prove the vehicle was at the accident
scene.

48. Selection of Soil and Rock Standards
The crime scene specialist should always obtain samples of rocks
and soil from the crime scene to be used as standards for
comparison with like substances that may come from a suspect.
Each sample should consist of approximately two tablespoons of
soil. When taking the sample, it is usually not necessary to go
deeper than ½ to ¾ of an inch. However, if a footprint, tire track, or
other indentation in question penetrates into soil that is different
from the topsoil, it may be necessary to obtain a sample of both the
topsoil and the subsoil.
If soil and rock evidence are found on a suspect’s shoes, a
comparison sample should be taken from the portion of the
footprint left at the crime scene corresponding to the area on the
shoe on which the evidence was found. Comparison samples
should be taken from a footprint, tire track, or other indentation
only after a plaster cast has been made

49. VI. Tool Marks as Trace Evidence
• Tool mark is type of evidence that involve
comparisons of known standards versus the
unknown. The manner in which the examinations are
conducted in the laboratory is often similar. The
crime scene specialist must not only be aware of the
wide array of both types of evidence, but also be
familiar with the proper methods of collecting it for
subsequent comparison purposes.

50. Two general types of Toolmarks
I. Toolmarks
Crimes against property frequently involve the use
of a tool in order for the criminal to gain entry into
the premises by applying force with the tool. These
toolmarks can be highly identifiable and be of
great evidentiary value.

51. • Definition.
a. Tools – any object capable of making an impression on
another object. Examples: axes, knives, chisels, crowbars,
pliers, cutters and drill bits.
b. Toolmarks – any impression, cut, abrasion, or gouge left by a
tool after coming in contact with an object.
Two (2) General Types
 Impressions - are those marks in which only the general form
and size of the tool are apparent. When a tool is pressed into
some type of material, it produces a negative impression.
These negative impressions, or marks may not make a
definite identification of the tool possible. However, they can
serve as a guide when it is necessary to decide whether or
not the tool of a suspect could have produced the marks.

52. 2. Striations – are those marks in which peculiar
characteristics or irregularities of the tool are
reproduced in the form of identifications or
striations. These marks are the most valuable as
evidence since they can sometimes positively
identify a particular tool to the exclusion of all
others.

53. How Toolmarks are Created
1. Compression - is a static identification made by
blows using a tool (e.g., hammer marks-sledge,
ball pen, claw; screwdriver pry marks; opposed
jaw marks made by pliers, bold cutters, pipe
wrench.)
2. Friction – is a dynamic mark, most often leaving
striations made by the unique edge irregularities of
a particular tool (e.g. shears, screwdrivers, knives,
axes, etc.)
3. Repetition- is the repeated dynamic marks left by
tools such as files or saws. These are very difficult
to identify because of the great number of teeth
and the confusion of marks left.
4. Combination – often tool can leave a combination
and friction marks.

54. Evidentiary Value of Toolmarks
1. Class Characteristics- Toolmarks left at the scene of
the crime usually will reveal microscopic
characteristics that can help reveal the class
characteristics of the tool that was used. The class
characteristics of a tool are usually considered to
distinguish it functionally from another. Therefore,
screwdrivers may be considered as a class part from
crowbars since they have different intended
functions. The class characteristics of tools serve as
a screening device in criminal investigations and
allow one to narrow the field of search which is
especially valuable in achieving positive
identification of the tool that left the impression.

55. 2. Individual Characteristics – Tools that are similar in
class characteristics are often quite different in their
individual characteristics. These individual
characteristics are derived from the processes used
to produce the tool and the manner in which the tool
has been used. Often, small burrs or nicks will
develop on the bit of the screwdriver, producing
individual characteristics of that tool. If the material
subjected to the toolmark is soft enough, it will
retain minute impressions or striations reflecting
these individual characteristics.

56. Searching for Tools and Toolmarks
1. Searching for Toolmarks-
The crime scene specialist should make a
conscientious effort to thoroughly examine the
scene of a crime to determine if any toolmarks
were left by the perpetrator. It is also important for
the crime scene specialist to search for any
evidence of a broken tool that may have been left
behind. If pieces are located, they must be
recovered since they can become valuable
evidence when the tool and suspect are located.

57. Crime scene specialists should ensure that they look in the
following areas for potential toolmarks:
1. Doors – Around the locking mechanisms, paying particular
attention to the wood of the doorframe and jamb.
2. Windows – On the bottom edge of the window, the sill and
framework of the window jamb.
3. Safes – All around the door, locking mechanism and hinges.
4. Drawers of desks, filing cabinets, or other secured drawers – Pay
particular attention to the area around any locks, as well as the
joining edges of each.
5. Wire fences exhibiting cuts- Compression marks from the cutting
device are often quite noticeable.
6. Cut locks- Brass locks are particularly good at retaining
compression marks from the cutting tool due to the soft nature
of the metal.

58. 2. Searching for Tools
The crime scene should be searched for any
obvious tools that were left behind, as well as tools
recovered from suspects. Each tool located should
be examined carefully and treated as potential
evidence. These tools have the potential to link the
suspect with the crime scene, depending on where
they are located.
3. Repetitive Tools
Crime scene specialists should pay attention to
repetitive tools that may have been left behind or
later recovered from a suspect. They should look
carefully for the following:
a. Material between the teeth of files or saws.
b. Separation of teeth.

59. Collecting Toolmark Evidence
1. Photography – Before any attempt to collect
toolmark evidence, it should first be photographed
in its original state. It is crucial that the toolmark is
permanently recorded before is crucial that the any
attempt is made to replicate or recover.
2. Original State – Whenever possible, every effort be
made to collect toolmark evidence in it original
state. Moveable objects such as cash registers,
small safes and cash boxes offer little difficulty
since the marks can be collected by recovering the
entire objects.
Sometimes, the entire object cannot be recovered
due to its size or construction. Marks found on a
window frame or door jamb can sometimes be
recovered by removing the damaged portion of the
object, particularly when the home or business
owner needs to replace it.

60. 3. Casting Toolmarks
When it’s impractical to collect an item containing a
toolmark in its entirely, the crime scene specialist
should consider using casting procedures to
replicate the toolmark. Making casts of toolmark
evidence will prevent the temptation to directly place
recovered tools into toolmarks to verify a match.
Great care should be used to ensure that the original
toolmark is not damaged or altered in any manner.
The crime scene specialist should never put a tool in
the mark – not only will it contaminate the evidence,
the potential exists to actually alter or destroy the
original toolmark, and possibly contaminate the tool
by transferring trace evidence from the toolmark to
the suspect tool.
Use silicone rubber (dental silicone may be used
quite successfully) for best result. Casts should be
used to make comparisons with tools or test marks.

62. VII.Shoe print and Tire impressions
as Trace Evidence

63. Shoe print and tire impression evidence is another
form of valuable physical evidence that is often
encountered at crime scenes. Since criminals must
either walk or drive to and/or from the crime scene, it
should be reasonably assumed that traces of
impression evidence will be left behind. The
recognition, collection, and examination of this
impression evidence can provide irrefutable proof of
the presence of an individual or a vehicle at a crime
scene or in contact with a victim.

64. The Value of Shoe Print and Tire Impression
Evidence
The characteristics of impression evidence that allow
for a comparative examination largely consist of
three (3) elements:
1. Design Characteristics
This is the basic pattern of the shoe sole or tire
tread design. These patterns are usually patented
although illegal copies or “knock-offs” are often
reproduced) and are somewhat specific to a
manufacturer. Usually many shoes or tires are
produced that have this basic pattern design.

65. 2. Wear patterns
As the shoe or tire is worn or used on a vehicle the
pattern area will wear down as erosion of the tread
or sole material takes place. This wear pattern
generally follows a somewhat “normal progression”.
However, other factors such as the gait or walking
pattern of an individual wearing the shoes, or the
front end misalignment of the tires on a vehicle or
the under or over inflation of the tires will have an
effect on the overall wear pattern. Although normally
the wear pattern alone will not provide the basis for
positive identification, it does impart some
individuality or agreement between the comparison
of the known shoe/tire and the unknown found at the
crime scene.

66. 3. Accidental Characteristics
During the normal use of a shoe or tire some
damage such as small cuts and nicks are imparted
on the tread or pattern surface. These
characteristics are known as “accidental” and occur
randomly on all tire and shoe designs commonly in
use. Assuming the agreement of the design
characteristics and wear patterns, the “match” of
accidental characteristics may allow for the positive
identification of a particular shoe or tire as having
made a particular impression.

67. Types of Shoe Print and Tire Impression
1. Two Dimensional
These impressions are usually found on a hard
surface that has been contacted by a shoe sole or
tire tread that has left behind or removed residue
or other materials. Details of the sole or tread
pattern can be seen on the surface . Impressions
that are made when the shoe or tire has deposited
or left behind residue are known as positive
impressions. Negative impressions occur when
preexisting residue is removed when contacted by
a shoe sole or tire tread.

68. 2. Visible Prints
These prints (impressions) are usually readily apparent an are
normally discovered during the preliminary stages of the crime
scene response. When a shoe or tire comes in contact with
either a liquid substance such as paint, grease, blood, water; or
a dry residue such as fire extinguisher powder, flour, safe
insulation; and then contacts a hard surface, a visible print will
be deposited. Usually these prints are fairly stable and can be
recovered during normal crime scene processing as long as
they are adequately protected from inadvertent destruction. The
exception would be if the print consists of water or a volatile
liquid (gasoline) that may quickly evaporate, documentation
and recovery should then be an immediate priority

69. 3. Latent Prints
These prints (impressions) are usually made when
relatively clean, dry shoes deposit or remove a very
thin layer of residue such as dust. Because these
deposits occur in trace quantities and often lack
contrast to the surface, they may not be readily
visible and are often overlooked. Searching the crime
scene with a strong oblique light source or making a
blind search with an electro-static lifting device may
reveal these impressions.

70. These impressions are created when a shoe sole or
tire tread contacts the ground or a soft surface with
sufficient force to cause a deformation of that
surface. The resultant impression is a negative
impression of the shoe sole or tire tread and will
reveal length, width, and depth characteristics.
Typically, these impressions will be photographed,
the surface will be prepared (stabilized) for casting,
the impression will be rephotographed and a plaster
cast will be made.
4. Three-dimensional

71. PHOTOGRAPHY
The photographic documentation of shoe print and
tire impression evidence is essential to permanently
record all characteristics and details of the
impression. In addition, the location of impression
evidence at the crime scene must be recorded to
allow for the future interpretation of directionality,
the relevancy of relationships to other objects and
items of evidence, etc.

72. A cast is a three-dimensional, properly oriented, life-sized
reproduction of the positive image of an impression making
object. Casts should always be made of three-impressions to
supplement the photographs.
CASTING
1. Impressions in sand and soil.
a. Dental stone is the preferred casting material and will
provide superior detail and tensile strength over plaster-of-
paris or other casting mediums.
b. Prior to casting, remove leaves, twigs, or loose objects that
may have fallen into the impression. Debris that is embedded
in the surface of the impression should remain .

73. 1. Spray with a fixative
The impression should be gently sprayed with a fixative
silicone spray aerosol (such as hairspray) to make the
surface inpervious to the liquid cental stonr that will be
poured in. If the impression medium is a very loose or
porous material it is desirable to spray several light coats of
gray primer paint over the impression. Again, being careful
to avoid disrupting the impression surface with the force of
the aerosol propellant.
2. Photograph the impression again at this point as more detail
may be highlighted by the addition of the fixative agent.
c. Preparation of the surface

74. d. Preparation and pouring of the casting material
1. The casting material (Dental stone or die stone) should be
ready for use in a disposable plastic Ziploc bag (8” X 12”
size). A pre measured portion of two pounds should be
divided into each bag.
2. Add 12 ounces of water to the bag and reseal. Massage the
mixture through the closed bag until it is thoroughly mixed
with no lumps and has the consistency of pancake batter.
3. The casting material should be poured on the ground
adjacent to the impression, and allowed to allow to flow
into the impression. Continue to add casting material
continuously until the impression is full and overflows.

75. 4. Case and impression identifies can be scratched into the
back of the cast as it begins to harden.
5. Allow at least 20 minutes for the cast to harden before
carefully attempting to lift it. Do not attempt to clean any
dirt or other materials that are adhering to the underside of
the cast at this point.
6. Allow the cast to cure for at least 48 hours before
packaging it in paper for storage or shipment to a forensic
laboratory.

76. The main function of the blood is transporting
oxygen, nutrients and wastes throughout the
body. Blood is approximately 8% of the body’s
weight. It consists of the liquid portion called
plasma (about 55% of the total blood volume) and
the formed elements, which are the red blood
cells (erythrocytes), the white blood cells
(leucocytes) and the platelets (thrombocytes),
The hemoglobin found in the red blood cells is
responsible for transporting oxygen to tissues
and carbon dioxide to the lungs. Serum is the
clear liquid that separates when blood is allowed
to clot.
VIII. Blood as Trace Evidence

77. Importance For the Study of Blood
1. As circumstantial or corroborative evidence against or in
favor of the perpetrator of the crime.
2..For disputed parentage
3. Determination of the cause of death and the length of
time the victim survived the attack.
4. Determination of the direction of the escape of the victim
or the assailant.
5. Determination of the origin of the flow of blood.

78. IX Latent Fingerprint as Trace
Evidence

79. Fingerprint Evidence

80. Fingerprint Evidence- continued

81. Fingerprint Evidence- continued

82. THEORY OF TRANSFER
“ When two objects come into contact, there will
frequently be a transfer of small amounts of
material from one to the other”. Thus, when
suspects come in contact with the victim and
objects at the crime scene, they frequently leave
behind traces of themselves and take with them
traces of any objects touched. Materials
transferred in this way are normally referred to as
TRACE EVIDENCE.

83. THANK YOU
AND
GOD BLESS