Forensic Science 1-Footwear and Tire Tread Evidence-University of Southern Mississippi

First Recorded Footwear Evidence Case

Occurred in 1792 (18th century) — a body was found near a boot impression with a worn nail pattern. The suspect’s boots matched the impression, leading to a murder conviction.

Common Oversight in Crime Scenes

Footwear impressions are the most overlooked evidence at crime scenes.

Fragility of Impression Evidence

Easily destroyed by weather, movement, or contamination — must be preserved, photographed, and collected carefully.

Common Substrates for Impressions

Mud

Freshly turned soil

Sand

Oil

Blood

Dust

Snow

Steps After Locating an Impression

Preserve

Photograph

Collect

Store properly

Comparison from Photographs

Possible only if photos are taken properly.

Proper Footwear Impression Photography

Take at 90° angle to impression

Take without and with scale

Scale level with bottom and same plane

Use tripod and oblique lighting

Fill the frame

Use RAW or TIFF format for comparisons

Collection Methods Depend On

Substrate type, location, and weather conditions.

Main Collection Techniques

Gel Lifters

Dental Stone Casting

Electrostatic Dust Lifter

Gel Lifters Purpose

Lift prints (footwear, fingerprints, dust impressions, trace evidence) from various surfaces.

Gel Lifter Colors

White, black, transparent.

Gel Lifter Use

Peel protective sheet

Apply gel to impression and roll out air

Peel off carefully

Replace clear cover

Advantages of Gel Lifters

Thick, low-adhesive gelatin lifts trace evidence without damaging surfaces.

Dental Stone Purpose

Best material for reproducing footwear/tire impressions in sand, soil, mud, and snow.

Mixing Ratio

1 lb dental stone : 6 oz water (ideal “pancake batter” consistency).

Casting Procedure

Photograph first

Place casting frame (optional)

Mix powder & water (in ziplock bag)

Pour outside-to-inside along leading edge

Harden for ~30 min (varies by weather)

Fully dry after ~24 hours

Common Mistake with Dental Stone

Using on metal—can conduct electricity and shock user.

Purpose

Lifts dust impressions from surfaces like floors, fabric, paper, doors, carpet, even skin.

Required Materials

Mylar film and metal plate.

Steps for Dust Lifting

Photograph first

Lay Mylar (black side down)

Connect dust lifter probes

Turn on current → film adheres

Roll out bubbles

Turn off and remove film

Protect lifted dust (nothing touches surface)

Storage for Dust Lifters

Place black side up in a cardboard box; tape corners to prevent movement.

Gel Lifters Storage

Store in paper or plastic with no heat.

Dental Stone Cast Storage

Use paper bag or cardboard box — fragile and can break.

Electrostatic Dust Lift Storage

Black side up in box, corners taped down.

Footwear/Tire Evidence Comparison

Conducted by a certified examiner trained in footwear and tire tread identification.

Certification Body

International Association for Identification (IAI)

Class Characteristics (Footwear)

Features shared by a group of shoes/treads.

Examples:

Size

Left or right shoe

Brand

Model

Individual Characteristics (Footwear)

Random, unique features linking to a specific source.Examples:

Wear patterns

Tread damage

Nicks/cuts

Missing sections

Sole plugs