1. Chapter 7

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

3.  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

4.  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)

5.  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

6.  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

7.  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