Your DNA Can Appear on People You Never Met, Things You Never Touched
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.
But van Oorschot’s paper also contained a vital observation: Some people’s DNA appeared on things that they had never touched.
In the years since, van Oorschot’s lab has been one of the few to investigate this phenomenon, dubbed “secondary transfer.” What they have learned is that, once it’s out in the world, DNA doesn’t always stay put.
The first time I heard about "secondary transfer" was on April 19, 2018, when I read KATIE WORTH's story on PBS's Frontline, about Lukis Anderson, a a 26-year-old homeless alcoholic man who was framed for a murder that he did not commit; nonetheless, Mr. Anderson's DNA was found on the victim's body. Meanwhile, the police and district attorney’s office began building a case with a narrative so convincing that Mr. Anderson began to believe that he actually committed the crimes. Being an alcoholic, Mr. Anderson couldn’t remember where he was at that time that the murder occurred; ironically, he was actually in a hospital detoxing, which that he couldn’t remember that he had a legitimate alibi.
I was astonished that I had never heard of secondary transfer before — forgetting the fact that I watch endless true crime stories, or that I’m a newshound who reads as much news as I can; by the way, that’s kinda the point of this entire website — because floating DNA is a phenomenon that scientists have known about for 20 years, that is, since DNA-tests became faithfully relied upon by law enforcement. This isn’t something that’s ever mentioned on Law & Order. As far as I ever knew, When someone’s DNA test comes back positive, both on true crime TV and real life, that’s pretty much a label for conviction; typically in these cases, even if the prosecutor’s case has holes, the narrative of the crime will be pieced together in the minds of the jurors, and the DNA match is always the basis for these guilty verdicts.
I wondered how many people might be convicted for crimes they didn’t commit because their DNA was found at the scene of a crime in which they took no part. And I began to research and I became astonished again when I learned that this is not even the first time that Mr. Anderson’s story has been told. His story had already been published in the New York Times.