Forensic Tire Impression and Tire Track Evidence Tire

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Forensic Tire Impression and Tire Track Evidence • Tire Impressions reflect the tread design

Forensic Tire Impression and Tire Track Evidence • Tire Impressions reflect the tread design and dimensional features of individual tires on a vehicle • Tire Tracks are relational dimensions between two or more tires: tracks can be used to determine the wheelbase of the vehicle

Tread Nomenclature and Sidewall Information

Tread Nomenclature and Sidewall Information

Tread Nomenclature and Sidewall Information • Department of Transportation number, known as DOT number

Tread Nomenclature and Sidewall Information • Department of Transportation number, known as DOT number – consists of:

Tread Nomenclature and Sidewall Information • Retread tires – have slightly different numbers •

Tread Nomenclature and Sidewall Information • Retread tires – have slightly different numbers • DOTR YPY 1201 • DOTR – Department of Transportation retread • YPY – Manufacturer retread • 1201 – date and year of manufacture

Tire Track Evidence • Tire track evidence consists of: – Tire track width –

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

RECOVERY • Tire impressions must be: – Photographed from all angles with and without

RECOVERY • Tire impressions must be: – Photographed from all angles with and without measurement tool (ruler) – Cast – a 3 foot impression requires 15 -25 pounds of dental stone – Measured – width, length and depth – Direction of travel noted – Impressions made if possible, and – Pictures of the source (tire) must be included for comparison

COMPARISONS • Tire tread examinations compare the tire impressions recovered from scene with tires

COMPARISONS • Tire tread examinations compare the tire impressions recovered from scene with tires taken from a known vehicle • Two categories of tires: – Suspect - Vehicle of suspect – Elimination - Vehicles of police, ambulance, etc • All tires should be seized from suspect vehicle for comparison

COMPARISONS • Forensic examination begins with visual comparison and elimination of tires which do

COMPARISONS • Forensic examination begins with visual comparison and elimination of tires which do not match impression • Forensic examination continues with full circumference test impressions • Impressions are superimposed on known impression over cast or original tire