How Many People Can Be Tracked Through DNA 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 using 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 their 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 now 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- and fourth-cousin matches in a database called GEDmatch, which includes information from about 1 million people. Meanwhile, Erlich and his co-authors show, in a database of that size, nearly 60 percent of people have a relative who is a third cousin or closer.

[Read: How a genealogy website led to the alleged Golden State Killer]

With the growing popularity of DNA tests, such databases are only getting bigger and bigger. It’s not hard to imagine being able to identify nearly every American through a relative’s DNA.

This is a boon for people taking DNA tests precisely to look for family. Years before police realized that genetic genealogy—the combination of family trees and DNA—could be used to ID criminals and unidentified victims, people have been using DNA databases to track down birth parents, sperm donors, and long-lost family. “It wasn’t a surprise to us at all. None of this has been a surprise to us. We have been using it for years and years,” says the genealogist Debbie Kennett. The Golden State Killer suspect’s arrest just woke everyone else up to the power of genetic genealogy.

GEDmatch, the database investigators used to find the Golden State Killer suspect and in subsequent cases, does not offer DNA tests itself. But it allows users to upload raw data files …read more

Source:: The Atlantic – Science

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