Footwear and Tire Tread Impressions Chapter 7 Impressions

Footwear and Tire Tread Impressions Chapter 7

Impressions One object makes physical contact with another and leaves some of its physical characteristics on the recipient Examples: shoe, fingerprints, tires, firing pins

Footwear Impressions Many shoes have distinctive tread patterns or are smooth Can be individual or class evidence ◦ Class evidence when shoes are new ◦ Individual when shoes are worn and have distinct markings and imperfections from being worn over time

Footwear Impressions Shoe deforms surface leaving impression Traces of material may be transferred from shoe to the surface (positive impression) or from the surface to the shoes (negative impression)

Footwear Impression Preservation Impressions are photographed with scale 3 -D impressions can be preserved using casting ◦ Fill impression with material that hardens and captures impression image ◦ Allow for direct comparison with known object

Tire Tread Impressions Tire tread ◦ part of tire that is in contact with road Can be class (new tire treads) or individual evidence (worn tire treads) Can tell you: ◦ wheelbase (distance from center of front wheel to center of the rear wheel) ◦ stance (distance from centerline of right tire to the centerline of the left tire) ◦ make and model of car

Capturing Tire Impressions can be positive or negative impressions Impressions should be photographed and casted ◦ Photographs can be more reliable than castings for tires if include measurements