Shoe prints and tire-tracks
Shoe prints and tire tracks are valuable forms of physical evidence often found at crime scenes, playing a crucial role in criminal investigations by helping to identify suspects and vehicles. Both shoes and tires exhibit complex designs, making them identifiable through specific characteristics. Investigators focus primarily on the outsoles of shoes, which may display logos, grooves, and patterns tailored for various activities, particularly in sports footwear. Likewise, vehicle tires have unique tread patterns that can be traced back to specific manufacturers due to patent protections on their designs.
Preserving shoe print and tire track evidence is essential, as these impressions can easily deteriorate or become contaminated, particularly in outdoor environments. Proper handling at crime scenes, including controlled access and timely documentation through photography, is critical for maintaining the integrity of this evidence. Techniques such as electrostatic lifting and casting in soft materials like mud or snow are employed to recover these prints effectively. While shoe prints and tire tracks generally possess class characteristics, they can develop individual traits over time, such as wear patterns or scratches, which provide investigators with crucial leads in solving crimes.
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Shoe prints and tire-tracks
SIGNIFICANCE: Evidence left by shoe prints and vehicle tires is commonly found at crime scenes and frequently contributes to solving investigations by helping to identify the suspects and vehicles involved in the crimes.
Shoes and tires are surprisingly complex and have many identifiable characteristics. Shoes are made up of many parts, but investigators are generally concerned only with the shoes’ outsoles, which are commonly known simply as soles. Many types of modern shoes—especially those manufactured for sports—have identifying logos or motifs on their soles. They may also have distinct grooves and divisions designed for specialized uses.
Vehicle tires are also complex and are commonly identified by their unique ridges and grooves. Because tire manufacturers patent the treads on their products, each unique tread pattern can appear on one manufacturer’s tires.
A key concern of the first investigators to reach crime scenes is preservation of possibly transient evidence. Shoe-print evidence can be especially sensitive to disintegration or contamination. Moreover, shoe prints are easily susceptible to destruction because they are often found outside primary crime scenes. To preserve such evidence, it is important to strictly control access to crime scenes and to establish entry and exit paths from the scenes that do not interfere with print evidence.
Shoe-print evidence and tire-track evidence should be photographed as soon as possible. Shoe prints found in dust can be lifted with a technique known as electrostatic lifting. Both shoe prints and tire-tracks made in soft surfaces, such as mud, can be cast in a variety of materials. Prints and tracks made in snow can be preserved with colored aerosols and photographed, or they can be cast with special materials.
Items of evidence found at crime scenes possess either class or individual characteristics. Evidence with individual characteristics—such as human fingerprints—can be matched to its source with a high degree of certainty. Evidence with class characteristics can be matched only to groups and not to particular sources. Both shoe-print and tire-track evidence possess class characteristics. However, as shoes and tires are used over time, they take on individual characteristics, such as nicks and scrape marks. Eventually, tires and shoes may develop distinctive wear patterns and leave impressions that indicate to law enforcement exactly which particular shoes or tires of the same types have made the impressions.
Bibliography
Adams, T., A. Caddell, and J. Krutsinger. Crime Scene Investigation. 2d ed. Upper Saddle River, N.J.: Prentice-Hall, 2004.
"Footprints, Shoeprints, & Tire Tracks." NC Prosecutors' Resource Online, 1 Dec. 2023, ncpro.sog.unc.edu/manual/641-1. Accessed 9 July 2024.
Genge, Ngaire E. The Forensic Casebook: The Science of Crime Scene Investigation. New York: Ballantine, 2002.
Houck, Max M., ed. Mute Witnesses: Trace Evidence Analysis. San Diego, Calif.: Academic Press, 2001.
‗‗‗‗‗‗‗. Trace Evidence Analysis: More Clues in Forensic Microscopy and Mute Witnesses. San Diego, Calif.: Academic Press, 2003.
"Tire Track & Footprint." ForenScope, 22 May 2022, forenscope.com/blog/forensic-science/tire-track-footprint/. 9 July 2024.