So much of our beliefs about “who done it” is conclusively wrapped up in the gold standard of identification, DNA. It’s not just all scienc-y, but good, solid repeatable science. Sure, there are tons of quibbles about the statistical likelihood of DNA being from a different person, contamination, magic-box testing and whatever other screw-ups humans bring to the lab, but when we’ve got it, we can take comfort in knowing that science says we got the right dude. Or better yet, they got the wrong dude, an innocent person, so cut him loose.
But there remains another nasty problem with DNA, that it doesn’t like to stay in one place.
Back in the 1980s, when DNA forensic analysis was still in its infancy, crime labs needed a speck of bodily fluid—usually blood, semen, or spit—to generate a genetic profile.
That changed in 1997, when Australian forensic scientist Roland van Oorschot stunned the criminal justice world with a nine-paragraph paper titled “DNA Fingerprints from Fingerprints.” It revealed that DNA could be detected not just from bodily fluids but from traces left by a touch. Investigators across the globe began scouring crime scenes for anything—a doorknob, a countertop, a knife handle—that a perpetrator may have tainted with incriminating “touch” DNA.
