Forensic Tire Impression and Tire Track Evidence

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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

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Tread Nomenclature and Sidewall Information
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Tread Nomenclature and Sidewall Information

• Department of Transportation number, known as DOT
  number consists of

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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

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Tire Track Evidence

• Tire track evidence consists of
• Tire track width
• Wheelbase dimensions
• Turning diameter
• Relative positions of turning tracks

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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

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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

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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