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Bodziak, William J. Shoe and Tire Impression Evidence. FBI Law Enforcement Bulletin. Vol 53 No 7 (July 1984). p 2-12.

Abstract: Impression evidence can be overlooked or destroyed by a hasty or disorganized search. Measure should be taken to locate, preserve, and properly collect this evidence for laboratory analysis. The first law enforcement officer, investigator, or technician on the scene should secure it.

When examining the scene, investigators should pay particular attention to tire and shoe impressions in areas of ingress, egress, and access where they likely will have traveled. To locate impressions that may not be easily seen on hard surfaces, thurn off the lights and direct a single strong beam at a low angle. This will often illuminate dust impressions. When located, impressions should be protected until they can be photographed and cast. All impressions, even if they appear "worthless" should be retrieved for evaluation.

Photograph impressions first in high-quality closeups from directly overtop the impressions at a distance of 2 to 3 feet. These can provide greater detail than a cast. The author recommends using a large size negative format, fine-grained slow speed black and white film, a tripod, a ruler or scale next to the impression, and proper oblique lighting at least three feet away. Several photographs with the light at different angles should be taken. Take care to correct for reflected light by adjusting the f-stop.

To cast an impression after photographing, remove debris that is NOT part of the impression. Erect a form around, but well away from, the impression. Class I dental stone is recommended as the medium with plaster of paris as a substitute. Prepare the dental stone with the proper water mixture, add dental stone until it ìcones upî in the center. Allow to stand for a minute or two so the stone will settle in, then stir until the consistence of thin pancake batter is reached. Pour the mixture over a spoon away from the impression and allow it to flow evenly over the impression. After 30 minutes of hardening, the cast can be removed. Do not clean the cast. Allow to air dry 24-48 hours. If casting an impression in snow with dental stone, stir in a small amount of snow or ice to lower the temperature of the dental stone and make the consistency slightly more viscous so it will not pass through the snow. "Snow print wax" can also be used in snow.

Hard surface impressions (tile floors, counters, glass, concrete) made with dust and residue should be photographed first as described above. Then the item with the impression should be collected as evidence. If it cannot be collected, the impression can be lifted with a footprint lift. Avoid makeshift lifting materials like contact paper. Follow the directions on the footprint lift package. Residue impressions may not transfer to a lift. Make sure they are photographed and the item collected, if possible. Dusting imprints with fingerprint powder is recommended only as a last resort.

Evidence shoould be packaged properly with description, type of examination desired, item number, and any background information. Labs can make comparisons to known footwear or tires and may be able to suggest the make and manufacturer of the shoe or tire. Instructions for submitting specific types of evidence are also included in the article.

For more information, contact:
Editor
FBI Law Enforcement Bulletin
FBI Academy
Madison Building, Room 209
Quantico, VA 22135

 
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