Enhancing the quality of aged latent fingerprints developed by superglue fuming: loss and replenishment of initiator

The recovery and identification of latent fingerprints from a crime scene are crucial to many investigations. The cyanoacrylate (superglue) fuming method (CFM), which develops fingerprints by growing a polymer coating over the print residue, is a powerful method but encounters severe limitations when prints are aged or exposed to harsh environmental conditions. We examine the aging process and how the changes that occur to a fingerprint residue over time influence the growth of polymer during development. We identify loss of initiator by erosion and degradation that, when coupled with a loss of water from the print residue, result in a decreased ability to polymerize ethylcyanoacrylate. Then, we present a methodology by which the ability of aged latent fingerprints to polymerize ethylcyanoacrylate is recovered. Two print enhancement agents, acetic acid and ammonia, are demonstrated to improve the growth of polymer from the print ridges by over an order of magnitude, while retaining the integrity of the print structure. Comparison between the two enhancement agents indicate that the enhancement occurs due to ridge coating by the ammonia or acetic acid and pH control of the latent print.     

Understanding the chemistry of the development of latent fingerprints by superglue fuming

Cyanoacrylate fuming is a widely used forensic tool for the development of latent fingerprints, however the mechanistic details of the reaction between the fingerprint residue and the cyanoacrylate vapor are not well understood. Here the polymerization of ethyl-cyanoacrylate vapor by sodium lactate or alanine solutions, two of the major components in fingerprint residue, has been examined by monitoring the time dependence of the mass uptake and resultant polymer molecular weight characteristics. This data provides insight into the molecular level actions in the efficient development of latent fingerprints by superglue fuming. The results show that the carboxylate moiety is the primary initiator of the polymerization process and that a basic environment inhibits chain termination while an acidic environment promotes it. The results also indicate that water cannot be the primary initiator in this forensic technique.