Tire tracks as evidence
Tire tracks serve as valuable forensic evidence often found at crime scenes, imprinted on semisoft surfaces like soil, mud, and snow. Analyzing these tracks can yield critical information regarding the size, weight, brand, and model of a vehicle, thus potentially linking a suspect's vehicle to the crime. The unique tread patterns left by tires, which include solid design elements and grooves, can be compared against extensive databases containing various tire designs, allowing investigators to deduce crucial details about the vehicle involved.
Furthermore, as tires wear unevenly, their unique use patterns can help positively identify a vehicle if located, by matching the wear on a suspect's tires with impressions found at the scene. Forensic scientists employ methods such as photography and casting to document these impressions, ensuring accurate analysis and preservation of evidence. However, the reliability of tire track evidence is sometimes debated within forensic circles, as matching processes may not provide definitive results compared to other forensic methods like DNA testing. Despite these challenges, well-documented tire tracks can be recognized as significant physical evidence in legal contexts, supporting investigative efforts in linking vehicles to criminal activity.
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Subject Terms
Tire tracks as evidence
DEFINITION: Impressions left by vehicle tires on semisoft surfaces.
SIGNIFICANCE: Tire tracks are often found at crime scenes, and analysis of such tracks can provide important information for investigators. Tracks can reveal the size and weight of a vehicle as well as the brand, model, and size of the tire; these details may link a suspect’s vehicle to a crime scene.
By examining tire tracks, forensic investigators can determine the distance between two or more wheels of a vehicle, which can allow them to estimate the size, weight, and wheelbase of the vehicle. In addition to this information, the tread impressions that tires leave in soft soil, mud, dust, or snow reveal identifiable patterns: solid design elements interspersed with grooves. Databases containing pictures of the thousands of different tread designs in existence are widely available, and forensic investigators can use these to find matches for the tire tread impressions found at crime scenes. By finding a tire tread match, investigators can deduce the brand, style, and size of the tire, which also gives them a general idea of the type of vehicle on which the tire is likely mounted.
Because tires on motor vehicles do not wear evenly, they develop unique use patterns. If a suspect’s vehicle is located, wear patterns seen in tire impressions from the can be compared to wear patterns on the vehicle’s tires, often with enough accuracy to identify the vehicle positively as having been at the crime scene.
Forensic scientists record tire tread impressions either by photographing them or by them. Photography is usually the method of choice when the impressions are less than one-fourth inch deep and tracks at the scene are not confusingly overlapped. Photographs are first taken of the general scene, to place the location of the tracks in context. A ruler is then placed next to each tread impression to indicate scale, and close-up photographs are taken. When impressions are photographed in snow, they are first gently sprayed with a product called Snow Print Wax or colored spray paint to increase contrast.
Casting is a method of making a three-dimensional copy of an impression. This is the method of choice for deep or confusing impressions. Powdered casting material is mixed with water and gently poured into the impression. After the material dries, it is removed from the scene and cleaned by technicians. The resulting cast can then be compared to tires in the tire design database or to tires on a suspect’s vehicle. Courts generally accept tire impression photographs and casts that match a suspect’s vehicle as physical that the vehicle was present at the crime scene.
The use of tire tracks as evidence is sometimes criticized by forensic investigators, some of whom believe that the process of collecting and matching tire patterns is difficult and unreliable. Unlike DNA evidence or other definitive processes, computer programs and scientific practices cannot definitively state whether a casting matches a particular tire. Instead, investigators must work to identify unique features, such as damage from a nail within a tread pattern, and argue that such unique features suggest that a casting or photograph is a match.
Bibliography
Baran, Madeleine, and Vogel, Jennifer. "The Questionable Science of Tire Track and Shoe Print Analysis." AM Reports, 27 Sept. 2016, www.apmreports.org/story/2016/09/27/questionable-science-tire-track-shoe-print. Accessed 18 Aug. 2024.
Bodziak, William J. Tire and Tire Track Evidence: Recovery and Forensic Examination. Boca Raton, Fla.: CRC Press, 2008.
Rainis, Kenneth G. Hair, Clothing, and Tire Track Evidence: Crime-Solving Science Experiments. Berkeley Heights, N.J.: Enslow, 2006.
Staggs, Steven. Crime Scene and Evidence Photographer’s Guide. 2d ed. Wildomar, Calif.: Staggs, 2005.
"Tire Track and Footprint." Forenscope, 20 May 2022, forenscope.com/blog/forensic-science/tire-track-footprint/. Accessed 18 Aug. 2024.