Image: The friction ridges on a finger (Photo courtesy of Wikimedia Commons).
A test protocol based on liquid chromatography-mass spectrometry (LC-MS) analysis accurately detects levels of illegal drugs in a single fingerprint from drug users while eliminating those who had only passive contact with a drug user.
In an earlier study, investigators at the University of Surrey (United Kingdom) described a test that used a fingerprint to detect cocaine use. Now, in a recent study, the group has improved on the earlier test by developing a new fingerprint protocol that detects both cocaine and heroin.
For this study, 100 fingerprint samples were collected from the hands of 50 nondrug users before and after handwashing to establish separate environmental cutoff values and testing protocols for cocaine, benzoylecgonine, heroin, and 6-monoacetylmorphine. The cutoff was challenged by testing the fingerprints of drug-free volunteers after shaking hands with drug users. Fingerprints from patients who testified to taking cocaine (n = 32) and heroin (n = 24) were also collected and analyzed. Analysis was carried out using the LC-MS gold standard drug testing method.
Results revealed that this protocol identified 100% of heroin users even after handwashing and gave a false positive for only one non-drug user who shook hands with a drug user. The investigators also used LC-MS to test for cocaine and its metabolite benzoylecgonine, which identified 85% of cocaine users after handwashing and produced no false positives for the non-drug users who came in contact with drug users. For both heroin and cocaine the fingerprint test correctly identified more drug users than saliva testing.
“The possibility of drug testing from a fingerprint has become the subject of many recent research articles, due to the ease and noninvasive nature of sample collection, as well as the fact that the donor’s identity is embedded within the ridge detail of the fingerprint itself,” said senior author Dr. Melanie Bailey, lecturer in chemistry at the University of Surrey. “This provides … the possibility of rapidly and noninvasively carrying out drug testing in a way that is difficult to falsify. This is, we believe, the first study to explore the significance of testing for drugs from a fingerprint, and therefore, the first effort dedicated to establishing an environmental cutoff.”
The study was published in the March 22, 2018, online edition of the journal Clinical Chemistry.
University of Surrey