Impression Evidence: Footwear

Impression Evidence

Pattern evidence is defined as objects or materials that have retained characteristics of other objects through direct contact.
Imprints are two-dimensional reproductions from contact with an object.
Impressions are three-dimensional reproductions from contact with an object pressed into a substrate.

Footwear impressions in soft materials like dirt, mud, sand, or snow are considered impression evidence.
Footwear impressions provide class and individual characteristics.
Reconstruction context evidence includes timeline, directionality, pressure, and rate of travel.
- Footwear impressions (outsole impressions) possess class characteristics such as brand, style, and size.
- Individual characteristics arise from specific wear patterns.

Individual traits create individual characteristics.
Factors like weight and height influence how a person walks.
Footstrike influences footwear patterns, causing different wear patterns on the soles.
- Neutral: Heel to toe
- Pronation: Fat foot, lot more pressure
- Supination: glides, less pressure
- Wear patterns help individualize shoes.
Individual wear patterns combine with foreign debris to create unique impression components.
- Bits of glass, punctures, and sediment contribute to the overall pattern.
- Each new piece of wear and tear adds uniqueness, similar to individualizing a fingerprint.
- Wet shoes from the snow can cause it to worp or curve the entire shoe like a C

Methods include:
- Lifting with tape or gel adhesive lifters.
- Lifting with an electrostatic device.
- Castings (only for impressions, not imprints).
  - 3D not 2D
- Photography.
Chemical reagents enhance class and individual characteristics of outsole impressions.
- luminol

Lisa Steinberg murder case (Jan 25, 1992):
- Murdered by gunshot and stab wounds.
- Initial arrest dismissed due to lack of evidence.
- A bloody outsole imprint provided key evidence, leading to conviction.

Ted Kaczynski (Unabomber) was aware of footwear impression studies and used forensic countermeasures.

Tire marks can be imprints or impressions depending on the circumstances.
- Skid marks on roadways are imprints.
- Tire tracks in loose sand, soil, snow, or mud are impressions.

Similar to other impression evidence.
- Photography is most common.
- Castings can be made of tire tracks.
Crime scene samples must be compared to known references.

Instrument that uses electrostatic charge to reveal indented writing on questioned documents.
Perpetrators often use notes (bank robberies, kidnappings, terror events) written on their own paper.
These documents contain valuable evidence:
- DNA.
- Latent Fingermarks.
- Indented writings.

Indented writing occurs when writing on a top sheet creates subtle impressions on the document below.
Visualized impressions may provide valuable investigative leads.
Documents are placed in a humidity chamber (60% humidity) for 15-20 minutes to introduce moisture.
The document is placed on the instrument's platen and covered with mylar film, held by a vacuum pump.
An electrical charge (~8kV) is imparted using a Corona wand, tearing air molecules apart.
Negative ions are attracted to the platen, charging the mylar film.
Glass beads coated with negatively charged black toner particles are poured over the document.
Toner particles are attracted to indented regions, visualizing the impressions as black lines or images.

Includes firing pin impressions, extractor marks, ejector marks, breech face marks, and bullet striations.

Tool usage involves the transfer of microscopic marks onto an impermeable surface.
Marks on tools come from:
- Manufacturing process (manufacturing marks).
- Use/wear, abuse, corrosion (wear and abuse).
Tools impart unique surface features, creating individual, reproducible tool marks.

Bitemark impressions on objects (and people) are another area of study and research.
Bite wounds are common in sexual assaults.
Forensic odontologists are key to securing criminal case convictions.
Theory: unique dental deviations develop over a lifetime, which can be cast and compared to bite wounds.
There are skeptics about the true, unique nature of the bite analysis.

Ted Bundy case:
- Accused of murdering Lisa Levy and Martha Bowman.
- No direct physical evidence at the scene.
- Lisa Levy's body had a bite mark on the breast and left buttock.
- A search warrant for Ted Bundy’s dental impression was issued and executed.