Fire Scene Evidence Collection Guide

Impressions

Known Tires and Tire Impressions

Detailed Procedure:

Tires are typically collected for identification and/or comparison to a questioned impression. If tires are being collected from a person's vehicle, be sure that any warrant and/or consent procedures have been followed.

To collect known tires and tire impressions:

  1. Photograph the tire while it is on the vehicle. Be sure to photograph the treads as well as the side wall of the tire, which contains information such as manufacturer, model, and maximum load rating.

  2. Wear new, unused, clean latex or nitrile gloves.

  3. Before collecting the tire, known impressions of the tire should be collected while the tire is on the vehicle. Ideally, this should be done on the vehicle the tires originally came on. The entire vehicle should be brought to the laboratory for processing. If this is not possible, you will have to take known tire impression in the field. Below is an example of one method for collecting known tire impressions; however, your laboratory should be consulted on their collection method preference:

    1. Obtain a number of pieces of chart board (available at art supply stores), so that, when laid end to end they measure at least as long as the circumference of the tire, usually about 7 feet. Also obtain printer's ink or latent print ink.

    2. Cut each chart board into 4 strips (1 for each tire) and tape them together length-wise to make 4 strips each approximately 7 feet long each.

    3. Starting with one tire, mark a starting position on both the tire and the chart board and, using your gloved hands, slather the exposed tread (not the portion on the ground) of that one tire with the ink. Place one of the 7-foot lengths of chart board in front of that tire and slowly drive or push the inked tire over the chart board. As un-inked areas of the tires become exposed, ink them. Continue this way until you complete one rotation of the tire. Make the impressions over cement or asphalt (smooth surface), if possible.

    4. Be sure to mark the direction of travel, the location of the tire on the vehicle (eg: driver's side front tire) and any other pertinent information on the inked chart board and the tire itself.

    5. When the ink is dry, package the chart board in an appropriate and properly labeled container, sealed with evidence tape. Initial and date the tape.

  4. After the known tire impressions are made, the tires can be removed and packaged. Be careful to preserve any trace evidence that may be lodged in the treads. Label the container with identifying information, including case number, date, exhibit number, a brief description, and your name. Insert the tire.

  5. Seal the container with evidence tape. Initial and date the tape.

  6. Store the item in a secure location, such as a locked evidence van or your vehicle, until you are able to transport it to the laboratory.

Laboratory examination of known tires and their tire impressions:

Known tires can be compared to questioned impressions left at a scene. Associations may be made by comparing tread design and tread design orientation. A positive match may be made if the questioned impression has sufficient individualizing or unique features (eg: cuts, nicks, wear pattern, etc.) in common with the known footwear. Evidence may be present in/on the tread (eg: soil, blood) that can be compared with known samples from the persons, places, and objects.

Source:

Crime Scene and Evidence Collection Handbook. Bureau of Alcohol, Tobacco, Firearms and Explosives. 2005.

"SWGMAT Web Site." Scientific Working Group for Materials Analysis, Website, July 1, 2013.

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