(CNN) - A free-to-use, publicly accessible genealogy and DNA database helped bring police a step closer to the man they believe is the Golden State Killer, a key investigator in the case told CNN.
Paul Holes, a recently retired investigator with California's Contra Costa County District Attorney's Office, said he took crime-scene DNA -- believed to be that of the culprit -- and entered the profile into the online Florida-based GEDmatch database.
GEDMatch is a site where people enter their own DNA profiles or genealogical data -- such as those you can get from DNA tests through paid services such as Ancestry -- and try to find familial matches with other users.
Holes said that when he entered the crime-scene DNA profile, more than 100 users matched as a distant relative, possibly as close as a third cousin. To use GEDmatch, users agree to make their information public and attach at least an email address to their profile.
Holes said investigators contacted "one or two people" as they tried to find, from the distant relatives, a pool of people who could have been the Golden State Killer of the 1970s and '80s.
Joseph James DeAngelo, 72, was arrested Tuesday in a Sacramento, California, suburb on suspicion of being the man who killed 12 people and raped more than 50 women in the 1970s and 1980s.
"This investigation lasted over 40 years, but with this course of DNA testing and matching, it took us only four months to get to the right pool of people," said Holes, who retired three weeks ago. "This guided us to the right pool of people without having to ruffle the sensibilities of a whole lot of people."
When DeAngelo's name emerged in what investigators believed was the pool of possible suspects last week, detectives used a different DNA sample -- one that was discarded -- and matched it to existing evidence from the investigation, law enforcement officials said Wednesday.
The Sacramento Bee first reported that police matched crime scene DNA to genetic material from a relative who was registered on genealogy sites.
Steve Grippi, Sacramento chief deputy district attorney, confirmed the news to CNN. Grippi told the newspaper that investigators spent a long time exploring online family trees before focusing the investigation on a suspect. He told CNN that other details in the Bee report are accurate.
Curtis Rogers, a partner with GEDmatch, said he learned about the site's link to the investigation through media reports.
"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," Rogers said in a statement. "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," he said.
DNA changed the case years ago, too
DNA played a key role in the investigation well before it was entered into GEDmatch.
Years ago, detectives believed the homicides in Sacramento and Southern California were connected but they could not prove it.
"But he would not leave fingerprints, so we could not prove, other than his M.O., that he was the same person. We did not know anything about DNA," said Larry Crompton, retired detective for Contra Costa County Sheriff's Department.
Once DNA tests were available, investigators were able to confirm the same man committed three of the attacks, Holes said.
In 2001, DNA evidence determined the East Area Rapist was the same offender as the Original Night Stalker. Now, the man is known as the Golden State Killer.
Note: Unless stated otherwise, the interviews from this story came from the HLN series "Unmasking A Killer."
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