Everywhere people go, they leave little bits of DNA behind. The saliva on a coffee cup or a stray hair can tell criminal investigators a lot about a person. Courts have said little about how much of a right people have to keep that genetic material private.
"Traditionally, the law has been that if you abandon your DNA, you lose it," says Barry Scheck, co-director of The Innocence Project. The group works to exonerate criminals it thinks were wrongly convicted.
Scheck thinks there should be a limit to what investigators can do with abandoned DNA. Comparing it to samples in a DNA database seems acceptable to Scheck, because it's "like comparing a fingerprint." But he believes "it would be quite another thing to start searching that DNA for more private information," such as familial connections or susceptibility to diseases.
There is little judicial history to tell investigators how extensively they can test someone's DNA once they have it. And courts have put few limits on how police can acquire your DNA.
"Somebody can't just come up to me and demand a DNA sample," says Doug Klunder, a Washington state ACLU attorney. But Klunder takes little solace in that fact because people inadvertently shed DNA all the time.
"At a practical level," Klunder says, "there is no protection. If law enforcement wants to get your DNA, they can."
No Privacy Rights for Discarded DNA?
Klunder recently wrote a brief in a Washington Supreme Court case, called Washington v. Athan, that highlighted this point. Seattle police suspected John Athan of raping and murdering a 13-year-old girl. The case had gone unsolved for more than 20 years. Detectives posed as a law firm and sent Athan a letter, inviting him to join a class-action lawsuit. When he responded by mail, the forensics lab tested the DNA where he'd licked the envelope. It matched the 20-year-old crime scene evidence, and police arrested him. Athan said the ploy was an illegal invasion of his privacy.
The Washington Supreme Court ruled six to three that "police are allowed to use some deception, including ruses, for the purpose of investigating criminal activity."
"No recognized privacy interest exists in voluntarily discarded saliva," the court found.
The dissenting justices called the ruling "breathtaking in its sweep." They said DNA is not just a matter of identity, but "contains the most intimate details about a person."
This has been a favorite theme of science-fiction movies, such as the 1997 film Gattaca, in which Ethan Hawke's character tries to pass as a genetically pristine person in a world where a DNA scan takes the place of a job interview. He eventually becomes a criminal suspect when police find his stray eyelash at the scene of a murder.
That scenario may seem less fictitious today than it did when the movie was released 10 years ago. But as Harvard professor and DNA expert David Lazer points out, police can learn at least as much about us through other means as they can through our DNA.
"One could build a very detailed profile of every single individual based on the information they make freely available through credit card use, through cell phone use, through paying taxes and the like," Lazer says. "It's very difficult to hide in this life that we live in the grid."