Tire Impressions Tire Impression Evidence What is tire

Tire Impressions

Tire Impression Evidence § § What is tire impression evidence? How is it involved in crime scenes? How is it collected? How is it analyzed?

Tire Impressions What are tire impressions or tracks? § Tire Impressions are the tread design and dimensions of a tire. § Tire Tracks are the related dimensions of the 4+ wheels.

Tire Impressions Different Types of Tires: Original Equipment (OE) Tires sold on new cars § thousands of cars have same brand size § Replacement Tires: purchased to replace old, worn tires § usually different than OE tires §

Tire Impressions Design Elements: Grooves: around a tire Slots: across a tire Sipe: small grooves Tread Wear Indicator: raised bar under design; shows after wear

Tire Impressions Noise Treatment: § If tire design was exactly repeated around the tire, noise would result. § Design repeated at different pitch lengths

Tire Impressions Tire Track Evidence: Track width: measured from right center to left center Track width of front tires and rear tires are not always the same.

Tire Impressions Tire Track Evidence: Wheelbase: measured from front center to back center

Tire Impressions Tire Track Evidence: Turning Diameter: Diameter of a circle made when the wheels are fully turned.

Tire Impressions Recovery of Tire Evidence: § Photos taken along with log of location. § Since tire tracks are variable along length (pitch), entire track should be photographed (examination quality) with overlapping photos. § Ruler included

Tire Impressions Recovery of Tire Evidence: § § § Cast can be made of 3 -D impressions Long sections (3 feet) should be cast. Use dental stone

Tire Impressions Analysis of Tire Evidence: Class Characteristics can be used to eliminate a suspected tire or suggest a tire could have made the track. Class Characteristics: Size § Tread design § § Some wear marks

Tire Impressions Analysis of Tire Evidence: Class Characteristics can be used to eliminate a suspected tire or suggest a tire could have made the track. Known tires collected. Inked or 3 D impressions can be made for comparison.

Tire Impressions Analysis of Tire Evidence: § Similar to shoes, individual characteristics can be used to identify an exact tire. § Remember, individual characteristics change over time. PPT from: www. centralia. edu/academics/forensicscience/fors%20101/. . . /ltire. ppt