Even people who have never taken a genetic test can be tracked down like the Golden State Killer suspect.
In April, the world learned that police had tracked down the alleged Golden State Killer by using a genealogy site to match DNA from crime scenes to that of his distant relatives.
The next arrest that resulted from the same technique—for a double murder in Washington State—came less than a month later.
And then another and another and another.
As the wave of reports went on, Yaniv Erlich, a computational biologist, was working to understand the reach of such police searches.
Were they lucky breaks? Or could nearly every American be found through a third cousin’s DNA? With every identification that made the news, Erlich had to update the paper he was working on. “It was like, every time, it’s a new case,” he says. By his count, the number of murderers, rapists, or unidentified persons found through genetic genealogy is up to 19—the latest announced just on Monday.
These cases are not exceptional, according to his analysis, now published in Science.
Golden State Killer investigators found their suspect through third-cousin and fourth-cousin matches in a database called GEDmatch, which includes information from about 1 million people.
In a database of that size, Erlich and his co-authors show, nearly 60 percent of people have a relative who is a third cousin or closer . . .