In this undated photo released by the FBI shows East Area Rapist Ski Masks in Sacramento, Calif. A California sheriff says a former police officer accused of being a serial killer and rapist was taken by surprise when deputies swooped in and arrested him as he stepped out of his home. Sacramento County Sheriff Scott Jones said deputies planned to arrest Joseph DeAngelo when he left his home on Tuesday, April 24, 2018. (Photo: FBI via AP)

The East Area Rapist/Golden State Killer/Diamond Knot Killer/Visalia Ransacker/Original Night Stalker terrorized communities up and down California for more than a decade, raping and killing people in their own beds, before disappearing entirely in the mid-1980s, just before forensic science was revolutionized by DNA.

But one of the DNA techniques of the 21st century has advanced so far that it was able to hunt him down to his very door: forensic genealogy through a public database, which has now cracked open a handful of notorious American cold cases.

Joseph James DeAngelo, now 72, became a suspect through a database lead found on GEDmatch, according to authorities. DeAngelo was arrested outside this home Tuesday after police focused in on him as a suspect based on a genetic link between the DNA at the decades-old crime scenes, and a sample one of his relatives must have uploaded to the public genealogy database, according to reports.

This undated law enforcement photo provided by the Sacramento County, Calif., Sheriff's Office shows Joseph James DeAngelo. DeAngelo, a suspected California serial killer who committed at least 12 homicides and 45 rapes throughout the state in the 1970s and '80s was identified Wednesday, April 25, 2018, as a former police officer, an official said. (Photo: Sacramento County Sheriff's Office via AP)

GEDmatch has been the source of huge other breakthroughs in decades-old cases: the existence of “Chameleon” serial killer Terry Peder Rasmussen, and most recently the long-sought identity of the “Buck Skin Girl” of Ohio.

But the Golden State Killer case has drawn the most headlines yet to the burgeoning science. And it remains to be seen how DeAngelo’s defense will debate the Fourth Amendment implications of the high-tech leads leading to his arrest.

DeAngelo, a former police officer, will be arraigned this afternoon in a Sacramento courtroom. He is believed to have committed 12 homicides, at least 45 rapes and more than a hundred burglaries over the course of a “reign of terror” lasting from at least 1974 to 1986, authorities allege.

The Sacramento Bee and other local news outlets report that Sacramento authorities used GEDmatch to find a relative, which led to the surreptitious collection of his “discarded” DNA over the last week.

(This genealogy technique is separate from familial searching, or FS, which involves looking for partial genetic matches in law enforcement databases like CODIS. FS was tried in the Golden State Killer case—but it had produced no hits, because no relatives close enough to DeAngelo had been convicted of crimes or otherwise been collected for the national database.)

GEDmatch is a public database used by many professional genealogists searching for family trees. It is for those who have their data sequenced in Ancestry or other services—but who want to see if it matches with people outside their own service.

GEDmatch is small—its 800,000 profiles are about a 10th of the estimated 8 million in Ancestry, according to experts.

However, its swath is wide enough to produce huge breakthroughs, according to Colleen Fitzpatrick and Margaret Press, the co-founders of the DNA Doe Project, which produced another major GEDmatch breakthrough this month with the identification of Marcia L. King, who had only been known as the Buck Skin Girl since her body was discovered by the side of an Ohio road in 1981.

For law enforcement, GEDmatch is a viable target. Since it is public, and its privacy rules make clear users are putting their information out there voluntarily, there are significantly fewer hurdles than with services such as Ancestry, 23andMe and MyHeritage, among others. 

GEDmatch told Forensic Magazine in a statement that users should be acquainted with their data potentially being used in criminal investigations.

“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,” the site stated. “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.”

Anne Marie Schubert, the Sacramento County District Attorney who was credited with organizing the statewide task force in 2016 that made the breakthrough, said at Wednesday’s press conference announcing the DeAngelo arrest that it was “innovative” DNA techniques which pointed detectives to the alleged Killer. The “lightning speed” developments all took place in the last six days, she said.

“It is fitting that today is National DNA Day,” said Schubert, at the time. “We found that needle in the haystack—and it was right here in Sacramento.”

Schubert said the Sacramento murder counts subject to today’s arraignment are for the February 1978 killings of Brian and Katie Maggiore. The Ventura County District Attorney, Gregory Totten, has mentioned that charges were forthcoming in the deaths of Charlene and Lyman Smith in March 1980. Tony Rackauckas, the Orange County District Attorney, cited the deaths of Keith and Patrice Harrington in August 1980, the February 1981 slaying of Manuela Witthuhn and the May 1986 rape and murder of Janelle Cruz as crimes DeAngelo will soon be charged with.