Forensic researchers at the University of Surrey have debuted a new fingerprint test using high-resolution mass spectrometry (HRMS) that is sensitive enough to tell if an individual has ingested cocaine or merely handled it. The difference is critical when you consider the legal ramifications of ingesting the Class A drug versus being exposed to the drug by environmental factors, such as handling money.
In 2017, Melanie Bailey and her team utilized the HRMS method to detect cocaine in the fingerprints of drug users, but did not consider the fact that 1 in 10 non-drug users are exposed to cocaine through environmental factors.
In the current study, the researchers took fingerprints from persons who had testified to taking cocaine during the previous 24 hours. Fingerprints were collected from each patient, and the participants were then asked to wash their hands thoroughly with soap and water before giving another set of fingerprints. The same process was used to collect samples from a pool of non-drug users who touched street cocaine.
Cross-referencing the data, the researchers discovered that a molecule produced in the body when cocaine is ingested, benzoylecgonine, is essential in distinguishing those who have consumed the drug from those who have only held it. Benzoylecgonine was not present in samples from drug non-users, even after touching street cocaine and then washing their hands.
However, limitations to the method do exist. While it provides better selectivity and relies less on chromatography, it is lab-based and therefore cannot be used in a roadside test by law enforcement.
“At the roadside it would be possible to carry out a screening test, but you would still need to collect a sample to take back to the lab for confirmation,” Bailey told Forensic.
Additionally, the experimental test as comprised can only tell the difference between contact and ingestion of cocaine if a person has washed their hands prior to leaving a fingerprint.
“Hands do need to be washed to make that distinction,” said Bailey. “For fingermarks left at crime scenes, it would not be possible to distinguish cocaine contact from cocaine use without the hand-washing.”
The researchers believe there is potential for the HRMS method beyond forensic analysis. They are, for example, researching the possibility of using a fingerprint to test the therapeutic level of a drug to ensure medication is delivered at the correct dose. According to University of Surrey researcher Catia Costa, the team has already shown that antipsychotic medications can be detected in fingerprints, and research is ongoing.