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SACRAMENTO — On March 29, as he prepared to turn in his gun and badge, longtime cold case investigator Paul Holes drove out to the Citrus Heights home of Joseph James DeAngelo, parked his car and sat outside.

Holes had been tracking the “Golden State Killer” for decades and it finally felt like authorities were closer than ever to solving the case. DeAngelo’s name was on a short list of viable suspects, and police in coming weeks would surreptitiously recover DNA samples that would connect him to the most notorious unsolved murder and rape spree in California.

DeAngelo’s daughter’s car was parked there too, Holes said, so he theorized the suspect was home. He thought about walking up, knocking on the door and going through a routine he’d done with countless men over his long career: apologize for the intrusion, explain their name had come up during the investigation and ask for a DNA sample.

But after some consideration, he drove home without ever having gotten out of his car. Looking back, he said that decision could have saved his life.

“He is a very dangerous man, and he had an arsenal of guns at his home,” Holes said. “And I was alone.”

If DeAngelo had ended up in a deadly confrontation with Holes that day, it wouldn’t have been his first time attacking an officer, according to police. During a press conference Wednesday, police identified DeAngelo not only as the “Golden State Killer” and the “East Area Rapist” — two of his many aliases — but also as the “Visalia Ransacker,” a serial burglar in the mid-70s who eventually committed a murder, and fired a revolver at an officer’s head as he escaped from one crime scene.

The Golden State Killer’s reign of terror included 12 homicides, 45 rapes and more than 100 residential burglaries between 1976 and 1986. His crimes began in the Sacramento area in 1976 and included the February 1979 killing of Brian and Katie Maggiore, who were shot while walking their dog in Rancho Cordova. He then moved to the Bay Area, where he committed 11 break-ins and sexual assaults in Concord, Walnut Creek, Danville, San Ramon, Fremont and San Jose in 1978 and 1979 before relocating to Southern California in 1979. Over the years, police identified 8,000 possible suspects.

Investigators compared DNA from the Southern California killings to samples available to law enforcement — including ancestry websites — and came up with a pool of people who were possibly related to the Golden State Killer. They began the painstaking task of eliminating each person through circumstantial evidence, and were left with a list that included DeAngelo and a few others.

“DeAngelo kind of bubbled to the surface,” Holes said. “We’d been looking at him and others for six weeks, and when others dropped off, the circumstantial evidence started to build up (against DeAngelo) and we decided we needed to get his DNA.”

It’s unclear whether DeAngelo will ever be prosecuted in the Bay Area rape cases. On Thursday, the Alameda and Santa Clara County district attorney said the statute of limitations prevents them from filing charges. Contra Costa County District Attorney Diana Becton was still reviewing how to proceed on nine rapes there.

Criminal defense attorney Dan Horowitz said there would be no way to prosecute the cases if there’s only enough evidence to allege rape.

“There’s no way to revive it,” Horowitz said. “And you really don’t want to be trying those cases anyway. It’s too painful for the victims, too painful for prosecutors and you’d want to save that for the penalty phase” of a murder trial.

However, if prosecutors could tie the rapes to torture or kidnapping, he said, the charges would become “life punishable,” which removes any statute of limitations. While torture is difficult to prove in court, Horowitz said a kidnapping enhancement would be a “cinch” if prosecutors can show the East Area Rapist tied up victims and moved them against their will.

Much has been written about the Golden State Killer; he’s been the subject of numerous books, a hit TV show on HLN that began airing earlier this year, and hundreds of articles — but few know the case better than Holes. A longtime police detective, Holes has a special passion for solving old cases and not letting go.

His involvement in this case began when he was an investigator with the Contra Costa County Sheriff’s Office and stumbled upon the case files of a serial rapist who had struck in the county in the late 1970s. Holes took it upon himself to pick up the case and linked the rapes to the Golden State Killer’s murder spree in Southern California.

About a year ago, Holes said, investigators began using new DNA technology that “allows the DNA to be a witness” and helps identify suspects who may be related. Authorities ended up with a short list of suspects that included DeAngelo.

“This has always been my one big case that I was spending most of my time on,” Holes said. “It was maybe a year ago when I realized that all the investigative strategies that I and others had employed just wasn’t cutting it, and trying to figure out how can we leverage the DNA technology.”

The day of the arrest, Holes got an unexpected call from a woman he’d spoken to only once. She was one of the Golden State Killer’s rape victims in Contra Costa, and she asked Holes if they’d caught the right man. He assured her they had.

“To me that’s the ultimate reward,” Holes said. “To make these victims feel safe and to get this guy who is the epitome of evil and end his life as he knows it.”

Staff writers Matthias Gafni and Angela Ruggiero contributed to this report.