For more than four decades, a suspect in more than 50 extremely sadistic rapes and 12 murders eluded police in Northern California. On Tuesday, he was arrested after investigators tracked him down using online genealogical databases that contained genetic information from a relative, news organizations reported Thursday.

The identification of 72-year-old Joseph James DeAngelo as the East Area Rapist began with the recovery years ago of DNA from a crime scene. Over the years, investigators compared the DNA to profiles on one or more undisclosed genealogy databases. Eventually, investigators found one or more distant relatives of DeAngelo's and traced their DNA to him. The Sacramento Bee, citing the Sacramento County District Attorney's office, reported here that the crucial lead came from "various websites that cater to individuals wanting to know more about their family backgrounds by accepting DNA samples from them."

The New York Times, meanwhile, said here that the match came from a commercial online genealogy database. The NYT continued:

"We found a person that was the right age and lived in this area—and that was Mr. DeAngelo," said Steve Grippi, the assistant chief in the Sacramento district attorney's office. Investigators then obtained what Anne Marie Schubert, the Sacramento district attorney, called "abandoned" DNA samples from Mr. DeAngelo. "You leave your DNA in a place that is a public domain," she said. The test result confirmed the match to more than 10 murders in California. Ms. Schubert's office then obtained a second sample and came back with the same positive result, matching the full DNA profile.

A former police officer, DeAngelo was arrested outside his home Tuesday afternoon and booked into Sacramento County Jail on two charges of murder. Authorities say they expect to charge the suspect in 12 homicide cases in Sacramento, Orange, Santa Barbara, and Ventura counties. The crimes took place during a rape and killing spree that ran from 1974 to 1986. DeAngelo is scheduled to be arraigned in Sacramento Superior Court on Friday.

In all, authorities have said they believe DeAngelo committed at least 51 rapes and 12 murders. The crimes gained international attention not only because of the number and their unsolved nature but also because of the depravity involved. The perpetrator frequently tormented his victims with sadistic rituals. He typically wore a mask and tied his victims' hands. Early on, he raped single women; and later he raped married women with their husbands present and then killed them both, the NYT said. Over the years, the East Area Rapist has also been referred to by other monikers, including the Golden State Killer and the Original Night Stalker.

Schubert and Jones have so far declined to reveal details of precisely how their investigations led them to DeAngelo, but they have said that information will be revealed soon. Representatives at 23andMe and other gene testing services said they weren't involved in identifying DeAngelo, the NYT said.