GEDmatch provides a more powerful way of tracing people by DNA and genealogy than a better-known method that only uses the Y chromosome. Fitzpatrick, Press’s partner in the DNA Doe Project, is an expert on this. In 2014, she tracked down the alleged “Canal Killer” in Phoenix, Arizona by matching the Y chromosome to a family name, which are both passed through fathers. Using age and location information, police then narrowed it down to a single man. However, this has severe limits, according to Fitzpatrick and Press. Y chromosomes cannot tell you how related two people are—even distant cousins with a last common ancestry in the 17th century may have essentially identical Y chromosomes. And, of course, it traces exclusively through the male line.
In fact, Fitzpatrick had tried using the Y chromosome to find the Golden State Killer. Michelle McNamara, the author of a recent book about his crimes called I’ll Be Gone in the Dark, consulted with Fitzpatrick after uploading his DNA profile to a Y chromosome database on Ancestry.com. The one match, however, was too distant to yield a useful lead.
“In this case, the Y chromosome definitely would not have led to him,” says Moore of the Golden State Killer case. “There’s much more power in autosomal DNA to resolve any sort of family or genealogical mystery.” Autosomal DNA refers to the DNA on the 22 pairs of other chromosomes that are not X and Y. With a web of enough matches or better yet one close match, an experienced genetic genealogist can begin to identify family members.
This work requires enough expertise that a professional genetic genealogist likely helped law enforcement—an idea that is deeply troubling to some in the community. “Because of the way this is done surreptitiously, there is also a lot of anger and backlash in our community,” says Press.
Press and Moore say they both know of genealogists making profiles on GEDmatch private after the Golden State Killer case became known. They fear that backlash from this case could make it harder for people trying to find family—or even police trying to find other suspects—in the future.
Given the power of genetic genealogy, a case like this was bound to come up. Even before it became public, Moore says, the community had been discussing a public statement about how law enforcement searches should be handled, but they could not agree. Now the debate has spilled out into the public.
“The question now is how we can work together so nobody’s privacy is invaded and it doesn’t damage our industry,” she says. “I would be devastated to see it come crashing down because of something like this.”