A man who police believe is the Golden State Killer will be arraigned Friday as police continue looking for more clues that connect him to the decades-old crimes.
Joseph James DeAngelo, 72, was arrested Tuesday and charged with capital murder in the 1978 killing of Katie and Brian Maggiore in Sacramento County.
On Thursday, FBI agents and police searched DeAngelo's home in Citrus Heights, a town about 16 miles northeast of the California capital.
Three days after DeAngelo's arrest, more details are emerging about what led authorities to believe he was behind the 12 murders and more than 50 rapes in the 1970s and 1980s.
Genealogy website helped crack the case
Authorities tracked down a suspect by comparing genetic profiles from genealogy websites to crime scene DNA, according to the Sacramento District Attorney's office.
Police matched DNA from a crime scene to genetic material from a relative who was registered on genealogy sites, Chief Deputy District Attorney Steve Grippi said.
Grippi told the Sacramento Bee, which first reported the news, that investigators spent a long period of time exploring online family trees before focusing the investigation on a suspect.
While it's unclear what DNA service was used, four companies contacted by CNN denied having any connection to the case.
Ancestry, Vitagene, MyHeritage and 23andMe said they didn't provide customer information to law enforcement officials.
Companies allow customers to take an at-home test and then send in their DNA. Scientists then compare the DNA to those they already have on record in hopes of connecting them with unknown branches of their family tree.
Suspect was a reclusive neighbor
DeAngelo -- the man accused of being the Golden State Killer -- is a former police officer, a Vietnam veteran and a mechanic.
He served aboard the USS Canberra, a guided missile cruiser, during the Vietnam War, according to Navy Public Affairs.
In the early 1970s, DeAngelo worked as a police officer in Exeter and Auburn. Authorities have said some of the alleged crimes of the Golden State Killer overlapped with DeAngelo's time as a police officer.
"Very possibly he was committing these crimes during the time he was employed as a peace officer, and obviously we'll be looking into whether it was actually on the job," Sacramento County Sheriff Scott Jones said.
DeAngelo was fired from his law enforcement job in 1979 for shoplifting a can of dog repellent and a hammer from a drugstore.
He went on to live what appears to be a quiet life. He worked as a mechanic at the distribution center of a Modesto-based supermarket chain for 27 years until he retired last year, a spokeswoman for the company said.
DeAngelo had at least three daughters, according Kevin Tapia, who has lived near the suspect for 20 years.
Neighbors have said DeAngelo mostly kept to himself and sometimes yelled at people who got too close to his fence but said he had become a recluse in recent years.
DNA's role in the investigation
Bruce Harrington constantly pushed California officials to use DNA testing, hoping it would help catch the man who killed his brother and sister-in-law nearly 40 years ago.
Many state elected officials and rights groups fiercely opposed any attempts by Harrington and the state to expand the California's criminal offender DNA database.
Critics cited the privacy rights of people in police custody and questioned the constitutionality of allowing the state to gather DNA samples without evidence of guilt.
Harrington spent years in front of public safety committees until California voters passed Proposition 69, known as the "DNA Fingerprint, Unsolved Crime and Innocence Protection Act," in 2004.
The proposition gave the state broader powers to collect DNA. Now, it could get samples from anyone not just convicted of a felony, but even arrested for one.
In some cases, authorities could also collect DNA from misdemeanor arrests.
The use of DNA technology in DeAngelo's arrest highlights the progress that law enforcement agencies in California have done in their use of forensic science.
"I began my quest in the mid 90s. It was 15 years until we heard that there was a DNA sample taken from our scene," Harrington said.