Free FBI Handbook of Crime Scene Forensics by Federal Bureau of Investigation Page B

area.
Casts will duplicate foreign material in the stamped characters. Clean the area before proceeding. Remove paint and dirt with a solvent such as acetone, gasoline, or paint remover. Use Naval Jelly to remove rust. Use a soft brush. Do not use a wire brush.
Build a dam around the stamped characters to retain the acrylic liquid while it hardens. Use a soft and pliable dam material such as modeling clay. Ensure there are no voids in the dam.
Following the instructions in the kit, mix the liquid and powder for one minute and pour the mixture into the dam.
The acrylic liquid will take 30 minutes to harden. Remove the cast when it is hard. If paint and rust are on the cast, make additional casts and submit the cleanest one to the Laboratory.
Indicate from where on the object (often a vehicle) the cast was taken.
Pack the cast to prevent breakage.
    Shoe Print and Tire Tread Examinations
    Shoe print or tire tread impressions are routinely left at crime scenes. These impressions are retained on surfaces in two- and three-dimensional forms. Almost all impressions, including partial impressions, have value for forensic comparisons. The examination of detailed shoe print and tire tread impressions often results in the positive identification of the shoes of the suspect(s) or tire(s) from the vehicle(s) of the suspect(s).
    Photographing Shoe Print and Tire Tread Impressions
    General crime scene photographs must be taken to relate the impressions to the crime scene. Examination-quality photographs then must be taken to obtain maximum detail for forensic examination and must include a scale. All impressions must be photographed using both methods.
    General Crime Scene Photographs
    General crime scene photographs of shoe print or tire tread impressions must include close-range and long-range photographs. ISO 400 color film should be used. The photographs must show the relationship of the impressions to the surrounding area. General crime scene photographs are not suitable for footwear or tire examinations.
    Examination-Quality Photographs
    Examination-quality photographs must be taken directly over the impressions using a tripod and lighting. A scale must be in every photograph. The purpose of these photographs is to produce a detailed negative that can be enlarged to natural size. Examination-quality photographs must be taken as follows:
Place a linear scale such as a ruler next to and on the same plane as the impression. Place a label in the picture to correlate the impression with crime scene notes and general photographs.
Images should be taken using a 35 mm or medium-format film camera. Low-cost digital cameras do not provide sufficient image detail for examination-quality photographs. Use a manual-focus camera. If the shoe print is made from a colored substance (e.g., blood), color film may be preferable to black and white. In most ambient-light situations, use ISO 100 film. Use ISO 200 or 400 film, if necessary.
Place the camera on a tripod and position it directly over the impression. Adjust the height of the camera, and if possible, use a normal lens (50 mm for a 35 mm camera). Fill the frame with the impression and scale. Position the camera so the film plane is parallel to the impression.
Set the f-stop on f/16 or f/22 for a greater depth of field.
Attach an electronic flash with a long extension cord to the camera.
Block out bright ambient light with a sunscreen to maximize the light from the flash.
Focus on the bottom of the impression, not on the scale. Take an existing- or reflected-light photograph.
Position the flash at a very low angle (10-15 degrees) to the impression. This will enhance the detail of the impression. For consistent exposure, hold the flash at least 5-7 feet from the impression. Shoot several exposures, bracketing toward overexposure to obtain maximum image detail. Move the flash two or more angles to the impression.
Take the exposures, move the light to another position, adjust the sunscreen, and repeat