NCJ Number
142487
Date Published
1990
Length
14 pages
Annotation
This paper addresses the application of laser-excited fluorescence in latent fingerprint development.
Abstract
The current mature procedures for laser fingerprint detection are described to set the stage for discussion of current research, which deals primarily with time-resolved imaging to take advantage of the difference between the lifetimes of substrate and fingerprint fluorescences. The principal procedure for laser detection of latent prints on smooth surfaces involves first the fuming with cyanoacrylate ester, which results in the formation of a polymer on the fingerprint residue. Thus stabilized, latent prints can then be solution-stained with fluorescent dyes. Porous items are treated with ninhydrin or its analogs, which react with amino acids of the fingerprint residue. Subsequent reaction with group II B metal salts yields intensely fluorescent products. Time-resolved imaging involves modulated laser excitation and gated imaging with a microchannel plate image intensifier. The critical requirement for such imaging is the identification of reagents or stains that yield lifetimes that are longer than those of the substrates and also at least comparable to the laser cutoff and image intensifier turn-on time. Two general approaches are presented. One involves compounds that yield long-lived intramolecular charge transfer states. The other involves chemical reactions with fingerprint residue that lead to formation of organo-rare earth complexes that display long- lived rare earth emission. 35 references