Proper photography techniques are essential to the documentation and analysis of impression evidence.
Following a few simple guidelines for close up impression evidence photography helps ensure sufficient detail is recorded, which in turn enables the examiner to conduct a complete and thorough comparison.
In general, crime scene track evidence documentation should include the basic series of photographs advised for all crime scene evidence: overall photographs, midrange photographs, and close-up or examination quality photographs.
Overall photographs include the tracks or impressions and relate their location within the general context of the crime scene. Midrange photographs relate the impressions to their specific location within the crime scene and to other nearby items of evidence, including other impressions. Overall and mid range photographs are important to document the position and orientation of impression evidence; however, they are not considered suitable for a complete forensic comparison.With the exception of being able to eliminate a shoe or tire based on an outsole or tire tread design that may be visible in an overall or midrange photograph, to conduct a complete comparison a high quality, properly composed close-up photograph of the impression should be taken.
For the photography of impression evidence, it is recommended that a professional SLR (single lens reflex) camera is used. A minimum of 8 megapixel resolution is recommended by the Scientific Working Group on Imaging Technology (SWGIT). Interchangeable lenses, detachable flash (with a 6 foot cord or remote capability), manual control of exposure, and remote shutter release are also recommended by SWGIT and by the Scientific Working Group for Shoeprint and Tire Tread Evidence (SWGTREAD).
A close-up photograph, or examination quality photograph, of a footwear or tire tread impression should be taken utilizing proper camera position, composition, scale, identifier, lighting, and be of sufficient resolution. Each of these aspects allows the most accurate and detailed natural size enlargement to be produced for the examiner to utilize in the comparison process.