ABSTRACT
Impression evidence presents itself in the crime scene in a number of forms. Tool marks, footwear or barefoot impressions, tire marks, and even bite marks routinely appear as evidence and require collection. Beyond documentation by close-up photography, casting is the primary mechanism of recovering impression evidence. The primary methods of recovering impression evidence that the technician should master are the use of rubberized casting compounds, an electrostatic dust lifter, plaster and dental-stone casting of both 2- and 3-D impressions, and the use of gelatin and other adhesive lifters. There are various methods employed to capture impression evidence. Physical casting is accomplished with silicone/rubber casting compounds and dental stone/plaster compounds. When presented with 3-D impression evidence such as tire and shoe marks in soil, an effective method of recovery is to cast the impression using dental stone. Casting in snow is another challenging process. One of the earliest methods developed for casting snow prints was the sulfur casting technique.
