Outwitting a drug test just got harder. Instead of relying on blood or urine, which can be switched, researchers at the University of Surrey have devised a technique that uses fingerprints to test for cocaine. And it not only tests whether a person has handled the drug; this new technique confirms cocaine actually entered the body.
The team from Surrey, joined by researchers from the Netherlands Forensic Institute (NL), the National Physical Laboratory (UK), King's College London (UK) and Sheffield Hallam University (UK), applied different types of mass spectrometry, which can measure the characteristics of individual molecules, to the fingerprints from a group of patients within a drug treatment program. The fingerprints were tested against each patient's saliva, to measure how the new technique stood up to traditional methods. Previous drug tests using fingerprints could only confirm cocaine had been in contact with a person's fingers. This new method takes it one step further.
"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 from the University of Surrey, Dr. Melanie Bailey says. "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."
DESI is a powerful new tool in chemical analysis that enhances the use of mass spectrometry. A sample is sprayed with highly charged droplets, ionizing the sample before it is transferred into the mass spectrometer. The process avoids fragmentation of the sample and has found use in forensics, chemical mapping, and explosives detection.
DESI could transform drug testing in the future. Traditional tests using blood require trained staff to obtain the samples. And anytime bodily fluids are used, be they blood, saliva, or urine, there are issues concerning privacy, biological hazards, storage, and disposal. Drug testing among law enforcement, prisons, courts, and probation services would benefit from a simpler, cleaner technique, which could eventually be made portable as the technology is refined.
"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," Bailey says. "By the very nature of the test, the identity of the subject is captured within the fingerprint ridge detail itself."
Researchers anticipate the development of portable devices within the next decade, which could aid police officers in identifying drug users.
"We are only bound by the size of the current technology," Bailey says. "Companies are already working on miniaturized mass spectrometers, and in the future portable fingerprint drugs tests could be deployed. This will help to protect the public and indeed provide a much safer test for drug users."
A full report is being published today in the journal Analyst.
