Whenever possible, impression evidence is collected as is and submitted to the laboratory for examination. Since there is only a slight difference between different shoe sizes, if the photographs are not taken at a 90° angle to the impression, then the true size cannot be produced in order to compare to the actual shoe. Properly photographing impressions is crucial.

Examiners may use alternate light sources or chemical enhancers to capture as much detail as possible, especially with latent imprints. In the case of impression evidence, general photographs of the evidence location in relation to the rest of the scene are taken, along with high-resolution images of the individual imprints or impressions. This includes securing and documenting the scene prior to collecting any evidence. Impression evidence is easily damaged, so steps must be taken to avoid damage to the evidence. (Courtesy of NFSTC)Īs with any evidence found at a crime scene, shoeprints and tire tracks must be properly documented, collected and preserved in order to maintain the integrity of the evidence. When that is not possible, for instance, if the print is on a bank counter, the examiner would use a lifting technique to transfer the imprint to a medium that can be sent to the laboratory.Ĭasts are created of footwear impressions to preserve them and allow for comparison and analysis. For imprints, examiners generally try to collect the entire object containing the imprint, such as a whole sheet of paper or cardboard with a shoe print. For impressions in soil, snow or other soft surfaces, casting is the most commonly used collection method. (Courtesy of Scott Campbell, Ron Smith & Associates) How Samples are CollectedĮxaminers use several methods for collecting footwear and tire track evidence depending on the type of impression found. Examples include shoeprints detected on a tile or hardwood floor, window sill, or metal counter, or tire tracks detected on road surfaces, driveways or sidewalks.ĭust impression left on a masonite surface, illuminated with oblique lighting. Examiners or investigators use powders, chemicals or alternate light sources to find these prints. This type is created through static charges between the sole or tread and the surface. (Courtesy of Aubrey Askins, Tacoma Police Department)Ī latent print is one that is not readily visible to the naked eye. This includes shoe or tire tracks left in sand, mud or snow.

(Courtesy of John Black, Ron Smith & Associates)Ī plastic print is a three-dimensional impression left on a soft surface. For example, bloody shoe prints left on flooring or tracks left by muddy tires on a driveway.īloody shoeprints are visible on tile flooring.

This type can be seen by the naked eye without additional aids. Prints are divided into three types: visible, plastic and latent.Ī visible print is a transfer of material from the shoe or tire to the surface. How It’s Done Evidence that May be Examinedįootwear and tire tracks can be deposited on almost any surface, from paper to the human body.

Bite mark impression evidence