3D footwear impressions in snow, sand, mud, dirt are one of the most visible evidence types especially in a climate such as Alaska’s. Before attempting to recovery any 3D impressions a series of photographs should be taken, these will complement any casts and document the impression in its original state, just in case the impression is destroyed during recovery. Before taking any photos any loose debris (that may have accumulated there after the impression was deposited) can be removed from the impression. Anything that is embedded in the impression, however loosely, should be left in place. Comprehensive photography of the crime scene including overall and mid-range photographs (including placards) should be taken. A close up photograph should then be taken from a 90° angle. The photo should ideally be taken using a tripod to ensure that it is perpendicular to the impression. The impression should fill the frame; this means the length of the footwear impression should fill the widest dimension on the screen of the camera. An L shaped scale should be placed next to and in the same plane as the impression. If the impression is 6” (15cm) down in fresh snow, you should dig a small trench 6” down next to the footwear impression (taking care not to cave the sidewall into the impression) and place the scale in it. Experiment with light from different angles to best illuminate the impression, around 10-20° usually works best. Take at least three photos using light from different sides as they will show different details within the impression. The placard number should be visible in the photograph.
If the impression is in snow/ice introducing contrast will help to get a better photo. To do this spray snow print wax or spray paint at a shallow angle around 6-10” (15-25cm) from the impression. A thin coat and oblique light will give the best results.