Footwear & Tire Track Examination
General information
How is it done?
footwear and tire track impressions = pattern evidence
- wich retailers/wich vehicles
- suspect
- identify type
Principles
3 main characteristics to analyze
imprints and impressions
Individual
Class
Wear
General class characteristics
Limited characteristics
from manufacturing process
= unique
= standard for every item
from use
damage (some examples)
a cut
a crack
stone or twig stuck in the tread
from natural erosion (caused by use)
examples
wear condition
the amount of depth of the wear
Why and When?
At almost any crime scene
Provides valuable information
Where?
Number of parties present
Direction?
Was on foot?
Connection to other crime scenes?
ex. of the most famous case involving shoeprints = 1995 O.J. Simpson murder trial
How it's Done
How Samples are Collected
Who Conducts the Analysis?
Evidence that May be Examined
How and Where the Analysis is Performed
3 types of prints
plastic print
latent print
visible print
= visible with naked 👀
ex. = bloody shoe prints left on flooring
= a transfer of material from the shoe or tire to the surface
= a 3D impression left on a surface
ex. = shoe or tire tracks left in sand
= visible with powders, chemicles or alternate light sources
ex. = shoeprints detected on a tile
= created through static charges between the sole or tread and the surface
Collecting entire object with prints/tracks
Lifting technique
Casting
adhesive lifter
Photographs (@ 90° angle to produce true size)
= lifts the imprints from smooth, non-delicate surfaces
gelatine lifter
Electrostatic dust-print lifting device
= a sheet of rubber with a low-adhesive gelatine layer on one side that can lift prints
= tool that electrostatically charges particles to put the print on a lifting film
The Scientific Working Group on Shoeprints and Tire Tread Evidence (SWGTREAD) = makes standards for footwear/tire track examiners
people who did 550 hours of training
= a well-trained footwear and tire track examiner
Tools and Techniques
Resources and References
Evidence Submission and Examination
comparing evidence with suspects imprints
ex. of tools = dividers, calipers, special lighting and low magnification
ex. of techniques = measuring the various elements, side by side comparasing, ...
database from the FBI
My own sources