For retired cold case investigator-turned-podcast host Paul Holes, the arrest of the alleged Golden State Killer, who had eluded capture for decades, was a turning point in his career.

Joseph DeAngelo, 73, was taken into custody in 2018 based on DNA evidence linking him to at least 13 murders and more than 50 rapes across California in the 1970s and ‘80s. He’s awaiting trial on 26 charges in a Sacramento jail since last April and has not entered a plea.

Holes, who was working on the case at the time, said DNA profiling techniques helped lead to an arrest. The Golden State Killer went undetected for years as he continued to break into his victims' homes to rape and murder them. It is believed his final victim was killed in 1986.

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“Once [DeAngelo] was placed in that interview room, he was in a posture that he did not move from for over an hour,” Holes recalled to Fox News. “He was absolutely motionless. He did a very slight movement and we’re like, ‘He’s moving!’ And then he would stop and freeze. I’ve never met anyone who’s been able to be so motionless for so long.”

“One of the female detectives said, ‘That’s what he was doing back in the day,’” continued Holes. “She was right. This was a guy who had the physical ability to go into somebody’s backyard, be in the shadows and just go absolutely motionless for hours while he’s watching what’s going on inside the house. Just seeing that, even though he’s an older man, you see this innate ability.”

According to authorities, the serial killer would sneak into suburban homes at night. If a couple was home, he would tie up the man, place dishes on his back and threaten to kill both victims if he heard the plates fall while he raped the woman.

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Holes started his search for the killer as a fresh police academy graduate and forensic toxicologist in Contra Costa when he was in his 20s, The Sacramento Bee previously reported. The case ultimately became a career-long obsession — even all the way up until his retirement.

“I was actively investigating him and in my last days of being active, I drove up to his house and parked in front of his house the day before I was retired,” said Holes. “In reflection, it’s a good thing that I did not go and knock on his door that day. I considered it. Just to get a DNA sample and eliminate this guy. But who knows what would have happened if he recognized me and decided to do something.”

Holes shared that at that time, he did not think DeAngelo was the murderer, at least not yet. He was simply another person he was looking to possibly eliminate as part of his ongoing search.

“After I retired, we were close,” said Holes. “The guys that were active, that were a part of my team, basically kept me on as if I hadn’t retired. When we finally got the DNA sample that showed he was the Golden State Killer, I was brought in. Even though I was a retired officer at this time, they brought me in. I helped write the arrest warrant… I also gave thoughts and ideas about interview strategies. In many ways, I’m very thankful they did that. Because I got a lot of satisfaction of being involved in that process when technically, they would have said, ‘Nope, you’re no longer part of us.’”

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Holes previously told the Mercury News in San Jose, Calif., that one of his team’s biggest tools was GEDMatch, a Florida-based website that pools DNA profiles that people upload and share publicly.

GEDMatch is a free site where users who have DNA profiles from commercial companies such as ancestry.com and 23andMe can expand their search for relatives.

Major companies, such as 23andMe and Ancestry, do not allow law enforcement to access their genetic data unless they get a court order, the Associated Press shared. Holes said officials did not need a court order to access GEDMatch’s large database of genetic blueprints.

“This investigative genealogy technique was everything to really catch him,” said Holes. “Using the information that we had in the case files, I went down so many different long paths, as did all the investigators… Using that DNA we had from the crime scene, it gave us the right direction. It gave us focus. So once we narrowed it down to a small group of individuals… It became pretty easy to figure out which guy it was. That turned out to be DeAngelo. Without this technique, I’m not sure we would have solved this case anytime soon… This case would have likely been an unsolved case today if I hadn’t stumbled upon this technique while I was involved with another case.”

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But Holes still has the urge to solve crimes. In fact, he recently teamed up with investigative journalist Billy Jensen to launch a new podcast titled “The Murder Squad,” which features unsolved cases of missing persons or murders.

The duo first connected through writer Michelle McNamara, who was researching the Golden State Killer case before her passing in 2016 at age 46. Jensen helped finish her book, titled “I’ll Be Gone in the Dark: One Woman’s Obsessive Search for the Golden State Killer.”

“For me, I spent all my time in the last few years of being active pursuing the Golden State Killer,” explained Holes. “I did not realize what a part of my life that case was until DeAngelo was taken into custody.”

“I just felt this void,” he continued. “I wasn’t on the hunt like I was before. And that’s something I just need. That’s part of what makes this podcast so exciting. We’re going after these cases. I’m getting into the hunt mode again. It helps fill that void. It’s not the same, but it’s at least something that I can grasp onto, knowing I’m still trying to help people get answers about their loved ones. It won’t ever be the same, but this is why I keep going.”

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Holes said the hope is that listeners will deliver in new tips and theories for him to follow-up on with Jensen.

“We have some cases were we interviewed family members,” said Holes. “They are just estate about the idea that their loved one’s case is still being pursued… They are all for it and have been very cooperative in terms of coming on our show and talking about what was going on with the victim and the victim’s life around the time the crime occurred.”

“There’s that possibility [listeners] can make a difference,” added Holes. “Just like I made a difference with the Golden State Killer… There are other individuals out there who have that same drive to make a difference.”

The Associated Press contributed to this report.

