1. Trace Evidence: Footwear & Tire impressions
Introduction to Forensic Science Unit 6

2. Objectives

3. Contents Types of Shoe Impressions Evidence from Shoe Impressions
Collection & preservation of impression evidence
Impression Databases
Introduction to Tire Treads
Tire Track Evidence
Collecting Tire Evidence
Characteristics of Tire Evidence
Conclusions from Tire Evidence
Tire Measurement Activity

4. Video Clips Footprints as Forensic Evidence 5 min
“Shoe-in for Murder” 21:19 min

5. 1. TYPES OF SHOE IMPRESSIONS
Trace Evidence –
Small particles that can be transferred between people or between a person and the environment.
Trace evidence can potentially be used to link a suspect/victim to a particular location.
Shoe Impressions –
A mark or outline made by pressing a shoe into a surface
There are three types of shoe impressions.

6. 1. TYPES OF SHOE IMPRESSIONS
Patent impression – visible, two-dimensional (ex. bloody shoeprints)
Latent impression – hidden, visualized by chemical or physical development
Plastic impression – three-dimensional imprints (ex. left in snow, soil, etc.)

7. Contents Types of Shoe Impressions Evidence from Shoe Impressions
Collection & preservation of impression evidence
Impression Databases
Introduction to Tire Treads
Tire Track Evidence
Collecting Tire Evidence
Characteristics of Tire Evidence
Conclusions from Tire Evidence
Tire Measurement Activity

8. 2. Evidence Clues from Shoe Impressions
Size of the footwear
Brand of the footwear
Sex of the wearer
Weight of the wearer (based on the depth of the impression)
The type of footwear (high heels, work boots, etc.)
What might you infer about a person from these clues?

9. Factors affecting shoe wear patterns
Walking habits (walking on toes or heels, feet straight or toes pointed in/out)
Body weight
Shape of the feet
Activities often engaged in
Surface walked on
Unique debris, holes, cuts
Walking habits (walking on toes or heels, feet straight or toes pointed in/out)
Body weight
Shape of the feet
Activities often engaged in
Surface walked on
Unique debris, holes, cuts
These can give you more clues about the wearer’s habits, activities, and lifestyle.

10. 2. Evidence from Shoe Impressions: Class characteristics
Characteristics that are common among similar articles of footwear
Examples:
size
tread pattern
brand

11. 2. Evidence from Shoe Impressions: Individual Characteristics
Unique characteristics observed only on an individual piece of footwear:
An unusual wear pattern
A pebble stuck in a part of the tread pattern
Damages (cuts, tears, abrasions, etc.)

12. Contents Types of Shoe Impressions Evidence from Shoe Impressions
Collection & preservation of impression evidence
Impression Databases
Introduction to Tire Treads
Tire Track Evidence
Collecting Tire Evidence
Characteristics of Tire Evidence
Conclusions from Tire Evidence
Tire Measurement Activity

13. 3. Collection & preservation of impression evidence
Photograph that includes a ruler for scale
Use a tripod and lighting to get a photo directly above impression

14. 3. Collection & preservation of impression evidence
Electrostatic lifting
Lifts footwear impressions from porous and nonporous surfaces without damaging the impressions
This device works on dry dust or residue impressions on clean surfaces 14 14

15. 3. Collection & preservation of impression evidence
Casting with plaster of Paris (CaSO4) or dental stone (on snow)
Dental stone sets at low temperatures without melting snow 15 15

16. Contents Types of Shoe Impressions Evidence from Shoe Impressions
Collection & preservation of impression evidence
Impression Databases
Introduction to Tire Treads
Tire Track Evidence
Collecting Tire Evidence
Characteristics of Tire Evidence
Conclusions from Tire Evidence
Tire Measurement Activity

17. 4. Impression databases
TreadMark
SoleMate 17

18. Video Clips Electrostatic Lifting 5:40 min
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Electrostatic Lifting 7:24 min v=Y-bxOYL7ppk
Casting Impressions 10:08 min Footprint%20Lab.html

19. Tire Impressions

20. Contents Types of Shoe Impressions Evidence from Shoe Impressions
Collection & preservation of impression evidence
Impression Databases
Introduction to Tire Treads
Tire Track Evidence
Collecting Tire Evidence
Characteristics of Tire Evidence
Conclusions from Tire Evidence
Tire Measurement Activity

21. 5. Introduction to Tire Evidence
Records of wheel impressions used as evidence in a court proceeding date back to the 1700s.
Tire evidence is commonly used and is accepted in courts in the US and around the world.
The FBI crime lab has used this kind of evidence and maintained reference files since its inception in 1932.

22. 5. Introduction to Tire Evidence: Tire Evidence Databases
SWGTREAD: Scientific Working Group for Shoeprint and Tire Tread Evidence
Established 2004
Works to standardize and advance the forensic analysis of footwear and tire evidence
A professional forum that meets twice yearly and is open to YOUR input!
TreadMate
UK database of tire tread patterns

23. Contents Types of Shoe Impressions Evidence from Shoe Impressions
Collection & preservation of impression evidence
Impression Databases
Introduction to Tire Treads
Tire Track Evidence
Collecting Tire Evidence
Characteristics of Tire Evidence
Conclusions from Tire Evidence
Tire Measurement Activity

24. 6. Tire Track Evidence
Tire impressions reflect the tread design and measurements of individual tires on a vehicle.
Tire tracks show relational dimensions between 2 or more tires.
Track width
Wheel base
Turning radius
These measurements could lead to a vehicle identification.
Note: There are often differences between front and back tires

25. 6. Tire Track Evidence: Tire Construction
Most tires made today are of radial ply construction
Tires are composed of
Liner
Sidewall rubber
Belts
Beads
Tread rubber

26. 6. Tire Track Evidence: Anatomy of Tread
Tread Blocks: segments that make up the majority of the tread. Their primary function is to provide traction
Grooves: voids for channeling water on wet roads
Sipes: small slit-like grooves on the tread blocks that increase their flexibility. Sipes also increase traction
Ribs: straight row of blocks that
create a circumferential contact
“band”

27. Contents Types of Shoe Impressions Evidence from Shoe Impressions
Collection & preservation of impression evidence
Impression Databases
Introduction to Tire Treads
Tire Track Evidence
Collecting Tire Evidence
Characteristics of Tire Evidence
Conclusions from Tire Evidence
Tire Measurement Activity

28. 7. Collecting Tire Evidence
3 dimensional casts
Using Plaster of Paris or dental stone (for snow)

29. 7. Collecting Tire Evidence
2D prints
Roll tire through ink and onto board to get a print of the entire circumference of the tire

30. 7. Collecting Tire Evidence
2D prints
Apply a very thin layer of Vaseline or shoe polish and make an impression on paper or board
Develop imprint with fingerprint powder

31. 7. Collecting Tire Evidence
Sometimes a tire impression may not be in dirt, snow, etc.
Some types of accidents, such as a hit and run, may leave tire marks on a body.
WARNING: The following picture is unpleasant…

32. 7. Collecting Tire Evidence

33. Contents Types of Shoe Impressions Evidence from Shoe Impressions
Collection & preservation of impression evidence
Impression Databases
Introduction to Tire Treads
Tire Track Evidence
Collecting Tire Evidence
Characteristics of Tire Evidence
Conclusions from Tire Evidence
Tire Measurement Activity

34. 8. Characteristics of Tire Evidence
Like footwear impressions, much of what is learned from tire impressions is class evidence
Make and model of tire
Size
Manufacture date and location
Tread pattern

35. 8. Characteristics of Tire Evidence
Tire prints and impressions can be individualized
Wear pattern
Damage like cuts or tears
Rocks or pebbles lodged in the tread

36. Contents Types of Shoe Impressions Evidence from Shoe Impressions
Collection & preservation of impression evidence
Impression Databases
Introduction to Tire Treads
Tire Track Evidence
Collecting Tire Evidence
Characteristics of Tire Evidence
Conclusions from Tire Evidence
Tire Measurement Activity

37. 9. Conclusions from Tire Evidence
SWGTREAD terminology defines 4 degrees of
matching of tire evidence
Identification: highest degree of association (rare). This opinion means the match is so exact that it excludes all other tires.
Probably made: very high degree of association. This opinion means the match is very persuasive but some critical feature is unavailable

38. 9. Conclusions from Tire Evidence
SWGTREAD terminology defines 4 degrees of
matching of tire evidence
Could have made: significant association of multiple class characteristics. There may also be some correspondence of general condition and wear
Inconclusive: limited association of some characteristics. This opinion means there are notable similarities, but limiting factors do not permit specific association between the questioned impression and known tire

39. Tire Track Measurements

40. Contents Types of Shoe Impressions Evidence from Shoe Impressions
Collection & preservation of impression evidence
Impression Databases
Introduction to Tire Treads
Tire Track Evidence
Collecting Tire Evidence
Characteristics of Tire Evidence
Conclusions from Tire Evidence
Tire Measurement Activity

41. Measurements
Are both front and rear tracks (and therefore track widths) always available in an impression?
Track Width: distance between 2 tires (such as between the 2 front tires).
Track width can be measured either from the centers of the 2 tires, OR from the right edge of one tire to the right edge of the other.

42. Measurements
Wheel base: the horizontal distance between the center of the front wheel and the center of the back wheel
This may not be available in a straight line track

43. Measurement activity Divide into groups of 3.
We will go to the parking lot and record the following for 4 cars
Front track width
Rear track width
Wheel base
Tire circumference of the right rear tire
You will then return to the lab and compare your evidence to a “suspect” sample.

44. Resources
Saferstein, Richard. Forensic Science: An Introduction. New Jersey: Pearson Prentice Hall, 2008.
Bertino, Anthony J. Forensic Science: Fundamentals and Investigations. Mason, OH: South-Western Cengage Learning, 2009.
Dr. Murray’s Footprint Lab
Federal Bureau of Investigation
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