Drug Use: Detecting it with a Single Fingerprint

Drug use is typically tested with invasive techniques that involve either saliva or urine, for instance, but now the presence of certain drugs in the body can be detected with a single fingerprint, according to a new study.

In this case, the new, non-invasive test, for the first time, could determine whether cocaine had been ingested, rather than just touched.

Led by the University of Surrey, a team of researchers used mass spectrometry to analyze the fingerprints of patients attending drug treatment services. They tested these prints against more commonly used saliva samples to determine whether the two tests correlated. While previous fingerprint tests have employed similar methods, they have only been able to show whether a person had touched cocaine, and not whether they have actually taken the drug - until now.

"When someone has taken cocaine, they excrete traces of benzoylecgonine and methylecgonine as they metabolize the drug, and these chemical indicators are present in fingerprint residue," lead author Dr. Melanie Bailey from the University of Surrey said in a statement. "For our part of the investigations, we sprayed a beam of solvent onto the fingerprint slide (a technique known as Desorption Electrospray Ionisation, or DESI) to determine if these substances were present. DESI has been used for a number of forensic applications, but no other studies have shown it to demonstrate drug use."

This breakthrough approach has potentially far-reaching applications for places that commonly rely on drug use tests, such as probation services, prisons, courts and other law enforcement agencies. That's because traditional testing methods have all sorts of limitations in the field. For example, blood testing requires trained staff and there are privacy concerns about urine testing. Where bodily fluids are tested, there can be biological hazards and often a requirement for particular storage and disposal methods. These tests also often require analysis off-site.

"The beauty of this method is that, not only is it non-invasive and more hygienic than testing blood or saliva, it can't be faked," added Bailey. "By the very nature of the test, the identity of the subject is captured within the fingerprint ridge detail itself."

The research team estimates that their new technology, which is described in the journal The Analyst, could see widespread use in the form of a portable drug test within the next decade.

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