Now could the same type of detective work on genealogy websites be used to catch another of California's most infamous and elusive criminals — the Zodiac Killer?
"It is possible," said Pam Hofsass, a former San Francisco homicide detective who worked on the Zodiac case and now runs the forensic lab for the Contra Costa County Sheriff's Office. "It's totally worth looking at, and I hope with all of the news and revelations about the Golden State Killer that it will kind of be the impetus for the Zodiac."
The Zodiac Killer roamed Northern California from December 1968 through October 1969, but was never caught despite at least one close run-in with police. He is known to have attacked seven victims, killing five — in Benicia, Vallejo, Lake Berryessa and San Francisco — and leaving two survivors. However, the Zodiac claimed responsibility for many more deaths in letters, often signed with a symbol of a cross over a circle.
Like the East Area Rapist, the Zodiac Killer took on an almost mythological presence in the psyche of Californians, and the story of his killing spree has been told in multiple books and movies over the decades.
Hofsass said one of the biggest hurdles to using DNA to track the Zodiac Killer is getting a clean genetic sample. She said evidence collection rules were much looser on crime scenes during the era when the Zodiac was active because DNA forensic science didn't exist. Often, multiple people would handle evidence without gloves, adding their own genetic material to collected objects.
"Back in the day, that was the protocol," Hofsass said. "It's not a clean sample, that's the problem."
She gave an example of a blood-soaked glove she found when she first started working on the Zodiac case around 2009. It was stuffed inside an evidence envelope and seemingly forgotten.
"I opened up the coroner's materials, and there was this envelope that said, 'Black Bloody Glove,'" Hofsass said.
The blood on the outside of the glove was identified as that of the Zodiac's last known victim, Paul Stine, a San Francisco cab driver shot in the head in the Presidio neighborhood in 1969, Hofsass said. But the blood and other matter collected from inside the glove was too muddled to be of use — possibly containing traces from anyone who had handled it over the years.
"We got a mixture on the inside," she said.
Tom Voigt, a recreational Zodiac expert who runs the website zodiackiller.com, said he believes a clean DNA sample could be taken from saliva that might be on envelopes mailed by the Zodiac. The serial killer was a prolific communicator, sending letters, cards and mysterious cyphers to media, law enforcement and others, including former Sacramento Bee reporter Paul Avery while he worked at the San Francisco Chronicle.
"I think Zodiac was definitely licking his own stamps and envelopes," Voigt said. "You just need to get the evidence, get it to the lab. Just copy what was done with the Golden State Killer."
Hofsass agreed that the envelopes could be useful.
"I think they are worth re-examing," she said. "That would go for all of the (law enforcement) agencies that received mail (and) taunting cards."
In 2002, that approach was attempted when ABC's "Primetime" asked a forensic expert from the San Francisco Police Department to compare a partial DNA sample authorities had from the surface of a stamp of a Zodiac letter with the DNA profiles of three men who were rumored suspects. That DNA analysis eliminated all three as suspects due to their significant differences with the sample. However, what was on the stamp provided only a partial genetic profile, and it wasn't strong enough to identify the killer, Voigt said.
A partial DNA sample also exists from evidence recovered from the Lake Berryessa murders, said Lt. Chris Carlisle of the Napa County Sheriff's Office. The Zodiac Killer attacked two college students, Bryan Hartnell and Cecelia Shepard, with a knife there in 1969. Shepard died but Hartnell survived, and Carlisle years later investigated the killing as a cold case.
Carlisle said physical evidence from that attack, including a car door and a blanket, were re-processed for DNA evidence in about 2010, but again the samples were found to be mixed and only a partial profile was obtained.
"There is always something when you get those mixtures, but separating it is the problem," Carlisle said.
But technology and techniques have improved. The East Area Rapist suspect, Joseph James DeAngelo, was identified when DNA saved from an old crime scene was associated with a distant relative on GEDmatch, an open-source genealogy site. Until recently, law enforcement limited DNA searches to databases of those with a criminal history. The use of the commercial site allowed investigators to virtually canvas a new pool of possible suspects, which included relatives of the killer.
From that hit, investigators from a federal and state task force tracked his family tree to narrow it down to men who lived in the vicinity of the crimes, eventually targeting DeAngelo in April.
Investigators then followed him to obtain two samples of "discarded" DNA from unidentified objects DeAngelo had been in contact with, according to Sacramento County Sheriff Scott Jones. Those samples matched crime scene DNA, leading to his arrest.
Voigt said he would like to see a similar joint-agency effort around the Zodiac Killer.
"If California law enforcement authorities would simply join forces as they did with the Golden State Killer ... then this would be a pretty big year because I don't think it would take very long to catch him."
Carlisle said his agency was not actively investigating the Zodiac case, but did follow tips as they arise.
FBI spokesman Prentice Danner said the federal agency considers the case "pending inactive," meaning it's not officially investigating it, but the case is not closed either.
San Francisco police did not immediately respond to a request for information about an investigation.
Hofsass said she was unaware of any agencies working collectively on the Zodiac case, but, "I would expect to see a renewed interest in forming some kind of collaborative effort," she said.
Alex Breitler, a former Stockton Record reporter, grew up in Benicia and said he first heard about the Zodiac Killer when he was in elementary school.
"He was your local boogeyman," Breitler, 40, said. "He was the Michael Myers of my town."
Over the years, Breitler has devoured information about the Zodiac case and has become something of an expert on his crimes. He said the arrest in the East Area Rapist case instantly made him think of the man who terrorized the Bay Area so many years ago.
"More than anything, it just reinforced for me that the potential really is there to finally crack the case," he said.