It turns out the thick, oily sludge our fingers smear on everything we touch leaves more than fingerprint impressions. Using mass spectroscopy, Sheffield Hallam University’s Simona Francese is testing fingerprint residue to determine other things from prints: the suspect’s gender, any food or drugs they’ve recently consumed, the presence of gunpowder residue, any health issues they may have, other substances they might have recently touched, and so forth. It’s not foolproof, but it can tell investigators more about a crime scene than they might otherwise know—and, even absent an actual fingerprint match, could be a great way to narrow down a list of suspects.
As of yet, forensic scientists haven’t been able to use fingerprint substance analysis to secure actual convictions, as the science behind it is very new; then again, so is the science of fingerprinting itself. The Smithsonian Channel explains where our unique fingerprints came from, and how scientists first discovered their forensic application, here:
And Francese’s fingerprint work isn’t just limited to substance analysis. As she explains here, it’s also quite useful in turning ambiguous smudge marks into clear, forensically valuable prints:
Looking at what can be accomplished with chemical analysis, you might ask yourself: can Francese pull DNA from ordinary fingerprint residue? Not yet—but a 2013 study found that fingerprint residue probably includes DNA, so there’s a very good chance that she or another researcher in the field eventually will.