Footwear and tire impressions are perhaps the most overlooked evidence at a crime scene. When impressions are collected it is possible that identifications can be made linking a suspect or vehicle to the crime. Impression evidence can be collected by casting (filling the impression with a compound that hardens and retains the shape and characteristics of the impression) and with photography. Photographs of impressions are often used to make positive identifications, but casting of impressions provides the best evidence. This is because impressions are three-dimensional and casting preserves three-dimensional evidence. The depth of tread and imperfections on the sides of the tread are preserved with casting. At major crime scenes impressions should be photographed before they are casted. Photography is done first because casting the impression will destroy the original impression and eliminate the ability to photograph the impression afterward. Also, photographs of an impression are taken in case there is a problem with the cast. If the casting fails, the photograph may be used to make an identification.

At minor crime scenes impressions are usually photographed without casting. If the impression is properly photographed positive identification linking a suspect or vehicle to the crime is possible.

When taking photographs of footwear or tire impressions begin with a photograph to show where the impression is located in the crime scene. It is important to include a recognizable landmark in the photograph so the location of the impression is understood. If the impression is near a landmark, such as in a flowerbed at the corner of a house, a mid-range photograph probably would be adequate to show the location of the impression. If the impression is farther away from a recognizable landmark, such as an impression on a dirt driveway twenty yards from the house, additional photographs would be necessary. An overview photograph showing the driveway with the house in the background would be followed with a mid-range photograph of the impression on the driveway. It may be necessary to include an evidence marker in both the overview and mid-range photographs to clearly show the location of the impression in the photographs.

There may be times where it is not possible to show the exact location of an impression with photographs. The impression may be located in an area with no recognizable landmarks nearby, such as in an open area of the desert. In this case the use of a GPS device (to give location) and a compass (to indicate direction the evidence is oriented) may be the only way to document the exact position of the impression. In such a case you could record the GPS information in your notes, and in the photograph of the impression include an arrow that is oriented to indicate north.

After photographically documenting the location of the impression you must take close-up photographs to show the detail of the impression. If you are using a film camera it is best to photograph impression evidence with black-and-white film. Black-and-white film provides more contrast and detail than most color films.

When photographing with a digital camera all photographs should be taken as RAW file images in color mode. RAW files are uncompressed and will capture more detail than JPG or TIF file images. By photographing in color, subtle tones that could be lost when photographing in black-and-white mode will be captured. Later the color digital photograph can be changed into grayscale in a program such as Adobe® Photoshop®.

To take a close-up photograph of an impression, place the camera on a tripod and position the camera so the camera's film plane is parallel with the impression. This will minimize distortion in the photograph. An angle finder can be used to measure the angle of the impression and then, by placing the angle finder on the camera's

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