Chapter 16: Tread and Footwear Impressions

Accidental characteristics

Unique marks from wear and tear on shoes ties to individual characteristics.

data bank

there is a data bank that holds info on different shoe impression that the RCMP store in their data base in order to cross reference the type of shoes with similar impressions

overtime

the composition of the shoe can alter as the shape changes, the Impression might change based on your whereabouts (rock stuck in shoe, defect, ripping of seems)

types of treads

- Tires marking with their patterns

- Footwear impressions (not unique to convict you put it is possible if you were convicted before)

Class characteristics

Common traits shared by shoe types.

- All shoes have common class characteristics

Footwear impressions

Marks left by shoes on surfaces.

Tread impressions

Patterns left by tire or shoe treads.

Patent vs latent

visible vs invisiible

Two-dimensional techniques

Methods for recovering flat impressions.

Three-dimensional techniques

Methods for capturing depth in impressions.

Two-dimensional Techniques:

• Slow visual search

• Oblique lighting

• Electrostatic lifting

• Dry origin impression

Electrostatic lifting

Technique to recover dust impressions.

Gelatine lifting

Method to withdraw prints using gelatine.

Three-dimensional Techniques

• Dental stone

• Sulfur mixture - snow

• Elimination and comparison images collection

• Compressible foam

Dental stone casting

Creating 3D impressions from footwear.

Incident to arrest

· If someone gets arrested 24 hours after offence, shoe print impressions & fingerprints are taken using test impressions (a foam) and step down to make

a comparison (Dental stone casting)

Vaseline

can put vaseline on surface, step on the

surfaced dust It to compare prints more

accurately.

Collect exemplars

• Victims, police, first responders, etc.

• Include all of suspects footwear as evidence

• Known impressions

• Assist in evaluation and comparison and elimination

What are types of

class characteristics?

Type of shoe patterns (running shoes, construction shoes, and heeled shoes)

Patterns on shoes (circle pattern, straight lines, and curved)

Examination of class characteristics

• 1st: Design or pattern

• 2nd: Physical size and shape

• 3rd: Wear characteristics - accidental marks

Tire tread impressions

Marks left by vehicle tires on surfaces.

Tire Tracks

Relative distance between two or more tires of a vehicle.

Track width

Measurement made from the center of one wheel or impression to the opposite wheel or impression.

Distance between the rear end and front of the tire tells us the type of vehicle it could be

Wheelbase

• Measurement between the centers of the hubs of the front wheels to the centers of the hubs of the rear wheels.

• Difficult for moving vehicles.

Turning diameter

Circle diameter made by fully turned wheels.

Impression evidence

Physical marks used for forensic analysis.

Visible impressions

Marks that can be seen without enhancement.

Footprint recovery methods

Techniques for collecting shoe impressions.

Tread Design Guide

Resource for identifying tire tread patterns.

Relative distance

Measurement between multiple tire impressions.

Exemplars

Known samples used for comparison in analysis.

Impression comparison process

Evaluating impressions side by side for matches.

Wear characteristics

Unique alterations from use on footwear.