Footwear and Tire Impressions

Another example of evidence used to link a suspect or vehicle to the scene of a crime includes footwear and tire impressions. An analyst examines the cast, photograph or lift of an impression left at the scene and the suspected shoe or tire to determine whether they share any class characteristics, similar tread design, size and/or wear characteristics or if any accidental characteristics are present on both. Class characteristics are those present in multiple items of the same type. Individual/accidental characteristics are those unique to a single item and allow a positive identification of that item.

For example, a shoe with gouges in the rubber on the bottom due to rough use will transfer that shape to surfaces that are walked on. Usually these patterns are unique and matching them to the shoe will result in a positive match (meaning only that shoe could have left the impression). 

Investigative lead information regarding the manufacturer and model of footwear or a tire can be determined from the design in the impression left at the crime scene. Reference collections and databases are used to develop this type of information.