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 technique developed 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.

The researchers say they hope to expand the range of controlled substances that can be detected, which could include methamphetamines, amphetamines, and marijuana. The test can be modified to detect therapeutic drugs prescribed by physicians too.

Needless to say, the technology has titillated law-enforcement and corrections officials, and it may have useful applications for professionals working in drug treatment, elder-care centers, and other inpatient and outpatient facilities. For all of its heady new potential, however, the emergence of technologies like these has some observers feeling a bit uncomfortable about how, where, and to whom they are likely to be applied. More pointedly, the ability to glean detailed information about a person from a mere fingerprint—Do they smoke cigarettes? Use marijuana? Enjoy fatty foods? Drink alcohol?—raises a number of potentially knotty questions of privacy and consent. And even within the criminal-justice system, some stakeholders worry that the emergence of these new fingerprint technologies could undermine what are already tenuous human rights.

“Oftentimes police will deploy these technologies without any consultation with the public,” said Camilla Graham Wood, a legal officer at Privacy International, a London-based organization that advocates for greater human rights around emerging technologies. Some law-enforcement agencies in the United Kingdom are already experimenting with field devices that can extract biometric data from fingerprints. “They’re relying on older, outdated laws that came into being long before these technologies were even considered,” Wood said. “So, it is unclear what legal basis they are relying upon.”

Wood said the police implementation of the fingerprint-based drug detection is an example of “technology for technology’s sake.”

“The bottom line is that police and law enforcement are excited about this new technology,” she told me. “They want to use it but don’t question, ‘Is it necessary?’ or, ‘How should it be done in a proportionate manner?’ These technologies have become very useful and convenient for the police. But that doesn’t make it acceptable or normal.”