August 8, 2008
Fingerprints' Chemical "Footprints"?
Today's New York Times reports a story that appears in this week's Science. According to the Times, "With a new analytical technique, a fingerprint can now reveal much more than the identity of a person. It can now also identify what the person has been touching: drugs, explosives or poisons, for example." See full story HERE. In short, scientists (Demian R. Ifa, et al.) have used mass spectrometry to identify fingerprints after subjects' fingers were applied with various solutions, including drugs and explosives residue. The researchers suggest that this technology might have several uses, including identifying what substances particular people might have handled recently and being able to distinguish overlapping fingerprints, by tracing the chemical "footprint" of the individual fingerprints.
Although there may yet be much value in this research, this single report hardly demonstrates its value for forensic purposes. The researchers essentially identified the true-positive rate for this technology, and, so far as either the Times or the original article in Science report, the researchers have provided no data on false positives, true negatives, or false negatives. Moreover, this study was a highly controlled laboratory study, so we don't know whether the technology might confront excessive "noise" when applied to the general population. Indeed, given the reported amount of drug residue on United States currency, mass spectrometry that is too sensitive is likely to produce large numbers of false positives.
Hence, while the research results reported here are interesting and noteworthy, without considerable more work in this area, they appear a long way from daily forensic use.