Fingerprints give away more than identity

The one-of-a-kind pattern of ridges and valleys in a fingerprint may not only betray who was present at a crime scene. It may also tattle about what outlawed drugs a suspect handled.

With advanced spectroscopy, researchers can detect and measure tiny flecks of cocaine, methamphetamine and heroin — in some cases as little as trillionths of a gram — on a lone fingerprint. The study, led by researchers at the National Institute of Standards and Technology in Gaithersburg, Md., appears May 7 in Analytical Chemistry.

Using an ink-jet–printed array of known quantities of drugs, researchers calibrated their spectroscopy techniques to measure specks of the chemicals. Then, using a 3-D printed plastic finger and a synthetic version of finger oil, researchers created drug-tainted fingerprints pressed onto paper or silicon.

On paper, the researchers detected as little as 1 nanogram of cocaine and amounts above 50 nanograms of methamphetamine and heroin. On silicon, the method picked up as little as 8 picograms of cocaine and heroin and around 1 nanogram of methamphetamine.

Researchers could also point to the location of the drugs on the fingerprint— at the peaks or dips of the pattern, for instance. Such information, the authors say, could help investigators finger what chemicals a suspect handled first and help corroborate a timeline of events in a crime.