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

Objectives

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

Video Clips Footprints as Forensic Evidence 5 min https://www.youtube.com/watch?v=7-esqwmLmCs “Shoe-in for Murder” 21:19 min https://www.youtube.com/watch?v=ZX2_XxIglhw

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.

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.)

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

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?

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.

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

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.)

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

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

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

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

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. Impression databases TreadMark SoleMate 17

Video Clips Electrostatic Lifting 5:40 min https://www.youtube.com/watch?v =WZu9qANTw_U Electrostatic Lifting 7:24 min https://www.youtube.com/watch? v=Y-bxOYL7ppk Casting Impressions 10:08 min http://science.marshall.edu/murraye/ Footprint%20Lab.html

Tire Impressions

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

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.

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

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

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

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

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”

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

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

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

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

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…

7. Collecting Tire Evidence

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. 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

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

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

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

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

Tire Track Measurements

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

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.

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

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.

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 http://science.marshall.edu/murraye/Footprint%20Lab.html Federal Bureau of Investigation http://www.fbi.gov/about-us/lab/handbook-of-forensic-services- pdf/ http://www.slideshare.net/jorgerpena/20-forensic-science- powerpoint-chapter-20-forensic-tire-impress#btnNext http://projects.nfstc.org/ipes/presentations/Bodziak_Footwear- Non.pdf Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. 

RESOURCES con’t. http://www.sonirodban.com/how-tires-are- made.html