In the fall of 1994, the United States was introduced to a new tool in the world of crime solving and prosecution — DNA evidence. The O.J. Simpson trial had captured the nation’s (if not much of the world’s) attention, and a large part of the trial’s outcome hung on DNA. At the time, the use of DNA evidence was still emerging, and the science wasn’t well understood — or trusted — by juries. (In September of 1994, the New York Times explored the issue. It’s a fascinating, contemporaneously-written glimpse into the history of law and science.) Even though the DNA evidence found at the crime scene in Simpson’s case was, by contemporary standards, almost certainly enough to secure a conviction, well, that’s not what happened.
But today, DNA evidence is almost always trusted and its findings dispositive. If a suspect’s DNA is found at a crime scene, he or she better have a good reason as to why. And on the flip side, the presence of someone else’s DNA (and the absence of the accused’s) can be used to demonstrate that the accused didn’t commit a crime. (Here’s a list of convictions overturned because of later-processed DNA evidence. There are a lot.)
So to summarize: if your DNA is at the crime scene, you’re in trouble; if someone else’s is there and yours is not, you’re in pretty good shape.
In January of 2009, a three-man jewel thief team pulled off a near-perfect crime. They broken into a Berlin department store named Kaufhaus des Westens and walked out with $6.8 million in goods. As TIME reported, the break-in was something straight out of a movie; “[the] masked, gloved thieves were caught on surveillance cameras sliding down ropes from the store’s skylights, outsmarting its sophisticated security system” — they couldn’t be identified on the security footage — and their latex gloves hid their fingerprints.
But one of the three robbers made a small and almost fatal mistake: he left one of those latex gloves behind. Authorities were able to pull a bead of sweat from it, and from that, get a read on the alleged thief’s DNA. Police ran the DNA through their database hoping to find a match. They didn’t find one.
They found two.
The police didn’t get very far. Neither brother was willing to rat on the other — and their lawyers did not want them held in custody indefinitely. So the brothers went to court, demanding they either be formally accused of the crime or released. ABC News reported on the court’s finding: “From the evidence we have, we can deduce that at least one of the brothers took part in the crime, but it has not been possible to determine which one.”
Unable to avoid the genetically-built-in “it wasn’t me, it was him!” excuse, the court had no choice: the brothers were set free.
From the Archives: Yes, You Can Get a DNA Match for the Dog Poop You Just Stepped In: Because sometimes, you need to know which of your neighbors isn’t cleaning up after Fido.
Take the Quiz: A quiz on DNA. It’s hard.
Related: “If I Did It,” by O.J. Simpson. 3.7 stars on hundreds of reviews. There’s a weird, weird back story to the book. If you click that link and look at the cover, you’ll notice a few things which don’t seem to be right. First, the title reads “I Did It,” with no “if.” Second, the authors are listed as Fred Goldman and Kim Goldman. Why? As Wikipedia explains, in 2007, a court awarded the rights to the book to the Goldmans, whose son Simpson was accused of murdering (and Simpson was later found civilly liable for his death). The Goldmans kept the book in print, but added the tagline “Confessions of the Killer” to the title and hid the word “If.” Click back to the book and you’ll notice that the word “If” is there — in small letters within the word “I” (from “I Did It”).