The break that authorities said led them to the man accused of being the Golden State Killer came when they linked DNA evidence from the slayings to genetic information contained on a consumer genealogical website, authorities said Thursday.
Investigators knew the killer only through a string of DNA recorded at several of the dozen murder scenes. Shaun Hampton, a spokesman for the Sacramento County Sheriff's Department, said officials had struggled for years to figure out whom that DNA belonged to. Recently, they tapped genealogical databases that the public uses to search for relatives and ancestors, he said.
Law enforcement sources told The Times that information from the websites dramatically reduced the the size of their search. Eventually they narrowed the investigation to several families listed in the database, with a pool of about about 100 men who fit the age profile of the killer, said the sources, who spoke on condition of anonymity.
Hampton declined to name the site used or provide details about exactly how authorities made the match.
The trail eventually led them to Joseph James DeAngelo Jr., a 72-year-old former police officer living in Citrus Heights, a suburb of Sacramento. The sources said the detectives then retraced his life, looking for connections between the numerous crimes across California and where he was during those times.
Private companies that provide ancestry searches from DNA samples submitted by paying participants usually also guarantee privacy for their users. However, customers are alerted to potential matches and can use the service to connect with possible relatives. The Sacramento County district attorney's office would not provide further details of its DNA evidence. The prosecutor's office is expected to provide more details of its case during a court hearing Friday.
Several popular DNA sites — Ancestry.com, 23andme and MyHeritage — all denied that law enforcement officials formally reached out to them about the Golden State Killer case.
It's unclear whether authorities submitted samples of the killer's DNA to the ancestry sites or used some other means of making the connection.
Unlike the federal DNA database that law enforcement uses in hopes of an exact match with a suspect, a commercial website generally provides broader information about a family tree, said Ruth Dickover, director of UC Davis' forensic science program.
It's highly likely a member of DeAngelo's family was using the site where the match was made, Dickover said.
"You'll get the most useful results from a parent or child of the person. As you go further away, it'll be less and less useful. A sibling is less useful, a cousin is less useful," she said.
Since authorities were looking for a man, investigators could immediately cut out half the results from their search. If the results produced a surname — a possibility if a male relative had submitted his genetic information — that too could narrow the search, she added.
"This was a shot in the dark, definitely," Dickover said. "If that's what they did, that approach is very new and innovative and explains how they were able to crack a case when the more traditional types of DNA testing couldn't."
Authorities say the Golden State Killer slipped in through backdoors and windows in the dark. First he struck in the foothills east of Sacramento, raping at least 46 women, before he began killing and headed south.
From 1978 to 1986, he killed 12 people in attacks ranging from the Sacramento County city of Rancho Cordova to the Orange County cities of Irvine and Dana Point. In Ventura, he tied up a couple with a drapery cord and raped the wife before fatally bludgeoning them with a fireplace log. In Goleta, he bound a doctor and his wife, a clinical psychologist, and shot them both.
The unsolved slayings were not linked with one another for years, and not linked to the rapes until 2000.
When authorities announced DeAngelo's arrest Wednesday, they said DNA evidence helped solve the case, but they provided few details.
Sacramento County Sheriff Scott Jones said a task force had been conducting surveillance on DeAngelo and secretly retrieved his DNA from a discarded item. The DNA matched the samples left by the killer.
California officials have been increasingly turning to so-called familial DNA to solve cold cases by scouring an offender DNA database for a father, son or brother of an elusive crime suspect.
Lab officials look for a relative by scanning genetic profiles in the offender database and looking for DNA samples that match with a suspect's along several, but not all, markers. From there, California's testing method focuses on part of the Y chromosome passed down along the male line, identifying father-son or full brother relationships.
Civil liberty groups have expressed alarm at the practice, saying the searches raise significant ethical and privacy concerns. Some questioned their legality.
In 2008, California became the first state in the nation to adopt a familial DNA policy. Under the policy, familial DNA is only to be used as a "last resort" when all other investigative angles have been exhausted. In some instances, detectives search the database several times for the same case. In the case of the Grim Sleeper killer, an initial search turned up nothing, but state officials ran another scan in 2010.
A partial match came back to a man added to the database after a 2008 arrest for firearm and drug offenses. Detectives zeroed in on the man's father, Lonnie Franklin Jr., who lived close to where many of the victims' bodies were dumped in South L.A.
There are few examples of law enforcement using commercial ancestry sites to track down suspects. Several years ago, law enforcement in Idaho used familial searching while looking for new clues in the 1996 killing of Angie Dodge — whose death drew widespread attention amid the belief that a man was wrongfully convicted of the crime. Authorities identified a new suspect, because the suspect's father had given his own DNA to a genealogy nonprofit whose forensic assets were purchased by Ancestry.com.
The suspect was eventually cleared, but it set off a firestorm of questions about whether the methods used to identify him violated his civil liberties.
Olu Orange, an adjunct assistant professor at USC and an expert on DNA evidence, said he's wanted to trace his ancestry through genealogical websites, but held back after reading their disclosure policies.
"I think people get excited about the service and the potential for what the service officers," Orange said. But "their privacy is out the window as soon as they send that DNA in."
Times staff writer Alene Tchekmedyian contributed to this report.
3:40 p.m.: Updated with background on DNA testing by police.
3:20 p.m.: Updated with more information from DNA testing firms.