Fingerprints are the oldest and most widely used biometric marker. Artifacts unearthed from ancient Babylon, China, and Persia show that fingerprints were often used on clay tablets and seals for business transactions and official documents. The loops, whorls, and arches that emerge from the “friction ridges” that form on a fetus’s developing fingers become unique to each person, and it’s no surprise that fingerprint identification has also been the gold standard in law enforcement and forensics since about the early 1900s. More recently, fingerprint verification technology has become almost ubiquitous in our daily lives as an access key for everything from smartphones and computers to bank accounts, offices, and even health records.
For all its utility, however, the image of this distinctive, swirling pattern has been the most information that you could extract from a fingerprint—though that’s starting to change. A raft of sensitive new fingerprint-analysis techniques is proving to be a potentially powerful, and in some cases worrying, new avenue for extracting intimate personal information—including what drugs a person has used.
That’s right: The new techniques can determine, from a single fingerprint, not whether you have handled these drugs, but whether you have taken them.
The new methods use biometrics to analyze biochemical traces in sweat found along the ridges of a fingerprint. And those trace chemicals can quickly reveal whether you have ingested cocaine, opiates, marijuana, or other drugs. One novel, noninvasive forensic techniquedeveloped by researchers at the University of Surrey in the United Kingdom can detect cocaine and opiate use from a fingerprint in as little as 30 seconds. The team collected 160 fingerprint samples from 16 individuals at a drug-treatment center who had used cocaine within the past 24 hours—confirmed by saliva testing—along with 80 samples from non-users. The assay—which was so sensitive that it could still detect trace amounts of cocaine after subjects washed their hands with soap—correctly identified 99 percent of the users, and gave false positive results for just 2.5 percent of the nonusers, according to a paper published in Clinical Chemistry.