Fluorescence in Forensic Science
Published Online: 15 SEP 2006
Copyright © 2000 John Wiley & Sons, Ltd. All rights reserved.
Encyclopedia of Analytical Chemistry
How to Cite
Menzel, E. R. 2006. Fluorescence in Forensic Science. Encyclopedia of Analytical Chemistry. .
- Published Online: 15 SEP 2006
Emission spectroscopy, which in the forensic science context historically has meant (carbon) arc spectroscopy, is occasionally still employed in paint examination and some other trace evidence areas, but has largely been replaced by atomic absorption (AA), Fourier transform infrared (FTIR), gas chromatography/mass spectrometry (GC/MS) and other analytical techniques. Notwithstanding its intrinsically very high sensitivity, molecular fluorescence spectroscopy is not utilized as a general technique of forensic analysis either, because spectra tend to be broad and featureless. Fluorescence spectral examination may occasionally be used in areas such as document examination, specifically for ink differentiation in instances of document alteration, but fluorescence spectra as such tend to pertain primarily to the arena of research. This is not to say, however, that the photoluminescence phenomenon is not exploited in criminalistics, the examination of articles of physical evidence recovered from the crime scene. Indeed, it is widely and effectively employed in tagging or labeling modalities and via the inherent fluorescence itself of trace evidence. Fluorescence-based approaches to authentication of currency and passports, identification of valuables, origin specification of gun powders and explosives, surveillance, and so on, are less directly pertinent to forensic science. These areas of fluorescence tagging will thus not be dealt with in detail. In criminalistics, photoluminescence is today the mode par excellence for ultrasensitive latent fingerprint detection. It is also employed in detection of body fluids, visualization of fibers, ink discrimination, and so on. Thus, the focus in this article will be on visualization and imaging. We begin, however, with discussion of the basic molecular photoluminescence phenomenon and description of some useful spectroscopic measurements, namely luminescence and excitation spectra, and luminescence lifetime determination by time-gated and phase-resolved techniques. These set the stage for the latest advances in photoluminescence visualization in physical evidence processing, with emphasis on fingerprints, the most prominent photoluminescence application in forensic science.