Cobalt Chloride Hexahydrate as an Enhancement Reagent for Two-Dimensional Footwear Impressions Containing Ice-Melt Product Residue

• Published in: Journal of forensic identification Vol. 66; no. 3; p. 196
• Main Authors: Karakkat, Kevin, Schwartz, Ted, Quarino, Lawrence
• Format: Journal Article
• Language: English
• Published: Alameda International Association for Identification 01.05.2016
• Subjects: Chemicals; Cobalt; Criminal investigations; Footwear; Forensic sciences
• ISSN: 0895-173X

Cobalt is a transition metal that is suitable to form coordination complexes with Lewis bases and is most commonly found as cobalt chloride hexahydrate. Given that ice-melt products typically contain moieties with free electron pairs (and thus can serve as a Lewis base), such as chloride salts or urea, the potential use of cobalt chloride hexahydrate as an enhancement reagent for footwear prints containing ice-melt products was investigated. Footwear impressions were made on nine different substrates from aqueous solutions of seven commercial ice-melt products of different compositions. To dried footwear impressions, an aqueous 20% (weight/volume) cobalt chloride hexahydrate solution was sprayed evenly. In most cases, a heated blow dryer was then applied over the imprint to turn the color of the enhancement from a lighter pink (the color of cobalt chloride hexahydrate) to the darker blue-purple (the color of anhydrous cobalt chloride), which typically yielded better contrast. Enhancements were obtained with all product compositions except one product containing calcium magnesium acetate. In general, diatomic chloride salts yielded better enhancements than those made from products containing monoatomic chloride salts. Products containing urea or proprietary formulations containing amides also produced good enhancements. The quality of the enhancement was likely affected by the porosity and texture of the substrate as well as the low viscosity of water.