Cost-Effective Alternatives to Casting Material for Large Scale Impressions

Abstract

Large-scale impressions are important evidence in crime scene investigations. Impressions come from many sources and may occur on any impressionable surface. Examples of large-scale impressions include tire treads, road scars, foot wear impressions, or even an impression of a depression from an exploded IED or shallow grave. Impressions can be made on a small scale from tool mark impressions and palm prints. The thorough documentation of impression evidence becomes difficult and costly when the impression is large. Research into cost-effective and timesaving methods of impression casting is needed so this valuable source of evidence in an investigation is not under documented. This study investigated the development of an alternative casting material for large-scale impressions from low-cost materials. Spray foam was tested individually and with releasing agents. Test formulations included various caulking compounds, fiberglass resin, acrylic, Mold Builder Liquid Latex and Monster Liquid Latex. A mixture of a latex-based caulking compound and liquid latex resulted in a pourable and thick casting material without the need of an additional releasing agent. The addition of calcium nitrate tetrahydrate in both solid and solution forms improved curing time, but the shortened curing time prevented an impression being made. Creating a compound to document large-scale impression evidence from low-cost, commercially available materials is possible, although further research is needed to solve the problem of long curing times.