Forensic Tire Tread and Tire Track Evidence

Tire tracks are important in forensic investigations and are usually found in road accident scenes or in the access and escape routes of other crime scenes.

Features to analyze: Tread pattern Width & depth of the tread pattern Wear pattern or defects

Tire databases are available help investigators determine the brand and model of the tire, which can be used to determine the type of vehicle that made the tracks.

Tire impressions reflect the tread and dimension features of individual tires on a vehicle

Contact Patch – portion of tire touching the ground

Stress Cycle – Under the load of a vehicle, rotating tire goes through stress

Tread Wear Indicator is a raised rubber bar 1/16 of an inch above base of grooves of tire

Noise treatment – tire industry created tire designs that vary the size of the spacing. This reduces or controls noise when driving.

Could two vehicles leave the same tire marks? Write out your answer in the space provided Explain why or why not. Be specific and provide examples!

Tire Track Evidence Tire track evidence consists of: Tire track width Wheelbase dimensions Turning diameter Relative positions of turning tracks

Track Width (Stance) – measurement made from one center of one wheel to opposite center of wheel

Wheelbase – measurement of center of hubs of front wheels to center of hubs of rear wheel Normally these measurements are not present at crime scenes

Tire Positions in a Turn When vehicle moves in straight path, only the rear tire tracks are available When a vehicle turns, rear and front tires track separately Important to understand and document at crime scenes

Front wheels turning produce unreliable measurements Rear wheels accurately record turns