Tool Marks
Any impression, cut, gouge, or
abrasion caused by a tool
coming into contact with another
object.
Identifying and Comparing Tool Mark

Careful examination of these of these
impressions can reveal important class
characteristics—size and shape of the tool.

Microscopic ridges and valleys
displayed on the tool are created
by the manufacturer, making
each tool unique.
(Similar to bullet striations)
Identifying and Comparing Tool Mark

Using a comparison
microscope, striation
marks from a test tool
can be compared to
the suspect tool.
Collection



The entire object or part of the object
bearing the tool mark should be
collected.
Otherwise, photograph or cast the tool
mark impression, though clarity of
details may be obscured.
Do not try to fit the suspect tool into the
tool mark impression, this will alter or
damage the impression.
Other Impressions

Different kinds of impressions can be found at
a crime scene:
Shoe print
Tire tracks
Fabric impression
Collecting Impressions



Primary consideration in collecting impressions is
the preservation for later examination.
Before any impression is moved or cast, it must be
photographed with a scale to show all observable
details as well as the relation to the overall crime
scene.
When the impression is on a readily recoverable
item, such as glass, paper or floor tile, the item
should be transported to the lab in tact.
Collecting Impressions

When the surface of the impression cannot be
transported to the lab, several other methods
may be used.
Fingerprint lifting
 Electrostatic lifting eg. Pathfinder
 Casting
 Aerosol cast for snow eg. Snow Impression Wax
 Chemical enhancement of bloody footprint

Lifting an Impression
An impression encountered on a smooth surface,
such as a wall, counter top, or flooring, can be lifted
similar to that of fingerprints.
A large lifting material covers the entire impression.
A fingerprint roller is used to
eliminate any air pockets
before the impression is
lifted.
Electrostatic Lifting
By creating an electrostatic charge,
the dust attaches to the lifting film.
One device is called the Pathfinder.
Casting
When a shoeprint or tire mark is found
in soft earth, casting is the best
preservation.
Class I dental stone is mixed with
water to form a paste.
Casting
The impression is outlined and the casting
mixture is carefully poured.
Casting
Once the dental stone has
dried, the walls are removed
and the impression is
carefully lifted.
Casting
Once the impression has air-dried
for 24-48 hours, it can be
shipped to the lab for
examination and comparison.
Casting Snow Impressions
Snow Impression Wax is an aerosol
product used to lift prints in the
snow.
Three light coats of wax are sprayed
onto the impression at an interval
of 1-2 minutes between layers and
then letting dry for 10 minutes
before pouring the casting
material.
Chemical Formulas
A number of chemicals can be
used to develop and enhance
footwear impressions made
with blood.
Some chemicals include amido
black, leucocrystal violet,
Hungarian Red dye, patent
blue.
Spray area well for several
minutes, then rinse with
distilled water. Take
photographs with scale.
SICAR
The Shoeprint Image Capture and
Retrieval is a computer software
incorporating multiple databases to
search known and unknown
shoewear files.
Bite Mark Impressions
Human bite mark impressions on skin
and food have been important
evidence in many cases.
A forensic odontologist can compare the
bite mark on the victim to a casting of
the suspect’s teeth.
Different lights and photographic
techniques are used.
Ultraviolet photos show damage
to the outer skin.
Infared photos show damage
under the skin surface.