Methylamine pretreatment of dry latent fingermarks on polyethylene for enhanced detection by cyanoacrylate fuming

Cyanoacrylate fuming is an effective routine technique for the detection of latent fingermarks on nonporous surfaces. The fuming mechanism involves the formation of hard, white polycyanoacrylate along the fingermark ridges, resulting in the detection of latent fingermarks on treated evidential items. Because the polymerization reaction is believed to be largely catalyzed by moisture, the inability to detect or develop some fingermarks is understandably attributed to dehydration of the deposit. Dehydration naturally occurs as the fingermark ages over time; such fingermarks are particularly problematic following exposure to harsh environmental conditions such as low humidity, ultraviolet light, or heat. Several pretreatment methods intended to reintroduce moisture to dehydrated fingermarks have been reported, including exposure to heated water vapor, acetic acid vapor, and ammonia vapor. If an effective method for reintroducing moisture to dry latent impressions can be developed and validated, then enhanced detection by cyanoacrylate fuming would result. This study was designed to investigate and compare published and novel strategies for pretreating dry latent fingermarks and to optimize the pretreatment application for polyethylene substrates. The most significant outcome was the enhanced cyanoacrylate response to dry latent fingermarks pretreated with vapor from 10% w/v aqueous methylamine solution. The results indicate that incorporation of an optimized pretreatment of this type into operational casework could potentially be the difference between unidentifiable fingermarks (lacking detail and contrast) versus fingermarks suitable for identification purposes