How genealogical websites helped investigators pinpoint alleged Golden State Killer

SACRAMENTO, Calif. (KGO) -- DNA Criminalists and law enforcement investigators are finding new ways to crack cases.

"Genealogy databases are good for more than just learning who your relatives are. They are good for solving cold case homicides," said Ventura County District Attorney Greg Totten.

RELATED: CoCo County Investigator Paul Holes is '100 percent sure' they have 'Golden State Killer'

The GEDmatch database was used to help identify alleged Golden State Killer Joseph DeAngelo.

When you register on the site now, the following statement comes up -

"We understand that the GEDmatch database was used to help identify the Golden State Killer. Although we were not approached by law enforcement or anyone else about this case or about the DNA, it has always been GEDmatch's policy to inform users that the database could be used for other uses, as set forth in the Site Policy ( linked to the login page and https://www.gedmatch.com/policy.php). While the database was created for genealogical research, it is important that GEDmatch participants understand the possible uses of their DNA, including identification of relatives that have committed crimes or were victims of crimes. If you are concerned about non-genealogical uses of your DNA, you should not upload your DNA to the database and/or you should remove DNA that has already been uploaded. To delete your registration contact gedmatch@gmail.com"

The Alameda County Sheriff's Office Crime Lab is not involved in the Golden State Killer case, but supervising DNA Criminalist Rhonda Roby explained how DNA can be used to trace a suspect when investigators don't know who the suspect is.

"So we generate a DNA profile from the evidence," said Roby.

RELATED: DNA linked Golden State Killer to murder of Fresno couple

Even a family member's DNA off a genealogical website could produce a match allowing investigators to narrow their search for a suspect.

Roby says a biological parent would present a 50% match.

"If I have a sibling, I'm going to share approximately 25% of my DNA, you go onto a cousin you're going to share less DNA but you're going to share a large percentage of it," said Roby.

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