Scott Peterson Protests His Innocence in Prison Interview in New Doc: 'I Didn't Kill My Family'

The inmate denies involvement in the deaths of wife Laci and their unborn baby in a new documentary, out Aug. 20

Sitting in the noisy dayroom of Mule Creek State Prison in Ione, California, as he speaks over a grainy video call, Scott Peterson looks more like a laid-back surfer than a man convicted of the heinous murder of his wife, Laci, and their unborn son Conner.

His hair, which he sometimes wears in a ponytail, is long and tousled, his demeanor calm and friendly. At one point he grows emotional as he recounts his memories of saying goodbye to Laci, then eight months pregnant, when he left the couple’s home in Modesto, California, on Christmas Eve morning in 2002 — the last time, he says, that he saw his wife alive.

“This past Saturday somebody made a mention [of the anniversary], and I was stunned,” says Scott, 51, wiping his eye. “A guy I never would expect to show humanity, a guy I was working in the kitchen with that day, brought it up.”

But in speaking out for the first time on camera since before his arrest 21 years ago, Scott is seeking much more than the sympathy of a fellow inmate.

In Face to Face with Scott Peterson, a new three-part docuseries premiering on Peacock on Aug. 20, the former fertilizer salesperson — now serving a life sentence without the possibility of parole — is once again denying any involvement in the disappearance and death of Laci and the child she was carrying. He is appealing to the public to listen to his side of the story of what he calls the “so-called investigation” carried out by police and prosecutors who he claims, ignored significant leads and relied solely on circumstantial evidence in their quest to convict him of double murder during his trial in 2004.

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Related: 'Scott Peterson Never Actually Denied Killing My Daughter to Me': Laci's Mom Sharon Rocha (Exclusive)

Says Scott: “I regret not testifying [at my trial], but if I have a chance to show people what the truth is, and if they are willing to accept it, it would be the biggest thing that I can accomplish right now — because I didn’t kill my family.”

The Peacock doc — one of two on Laci’s murder to be released this month — also chronicles the appeal launched last January by the Los Angeles Innocence Project in an attempt to overturn Scott’s conviction by proving his innocence.

And as one of Scott’s staunchest supporters in the documentary, his sister-in-law Janey Peterson, who became a lawyer in part to fight for his freedom, tells PEOPLE the project is also an opportunity to offer the public an alternative theory of what may have happened to Laci.

“My belief in Scott’s innocence isn’t based solely on what he claims,” she says. “My belief is based on the evidence."

It was shortly after 6 p.m. on Dec. 24, 2002, when Scott telephoned the Modesto Police Department to report his wife missing. By the time detectives arrived at the couple’s home, nearly three dozen friends, family members and neighbors had already frantically fanned out in the quiet suburban neighborhood looking for Laci.

Scott told police that he had last seen his wife that morning at 9:30 a.m., when he left to drive 90 miles to go fishing in San Francisco Bay. In the documentary, he shares “the things that I relish” from that final day.

“I would see Laci smile when she would do her hair on the morning of the 24th, and the way we would share a bowl for cereal because we were too lazy to do two bowls,” he says. “Just those little things are still with me.”

Investigators interviewed in the doc say they quickly focused on Scott in part because, statistically, husbands, boyfriends and other intimate partners are often guilty of violence against women. But Scott also aroused authorities’ suspicions because of his relaxed manner and his referring to Laci in the past tense in his first conversation with police.

Scott claims that Modesto Police detective Allen Brocchini, a lead investigator on the case, “made up his mind before he even arrived.”

Detectives questioned the authenticity of an affectionate voicemail that Scott left for Laci as he was driving back to Modesto earlier that day —and suggested he had left the message after he had killed Laci to establish his alibi.

Looking back on that today, Scott is indignant. “They opine that it was too sweet of a message for a married couple,” he says. “They have really sad marriages if they think that. Frankly, I feel bad for them.”

On Dec. 30, 2002, the investigation took a dramatic twist when detectives learned that Scott had been engaged in an extramarital affair with a Fresno, California, massage therapist named Amber Frey.

Scott admits today that he made a terrible mistake. “It’s horrible,” he says. “I was a total a-hole to be having sex outside our marriage.” But he insists he didn’t tell police he was in a relationship with another woman because he wanted to keep the focus on finding Laci.

“During the so-called investigation, I really did everything I could to bring my family home,” he says. “That includes keeping my cheating with Frey from people. I didn’t tell people because I wanted the search to continue.”

On April 18 — days after Laci’s and Conner’s decomposed bodies washed up on a shoreline roughly two miles from where Scott claimed to have been fishing — he was arrested in La Jolla, California.

He had bleached his hair blond and was carrying $15,000 in cash, a baggie filled with Viagra pills, camping gear and four cell phones in his car. Police claimed he was just 30 miles from the Mexican border and preparing to flee.

“I don’t understand that at all,” says Scott, who explains that he was visiting family in San Diego and had dyed his hair to avoid being recognized and verbally attacked by members of the public. “I just want to be clear — I was never running from the police.”

During his five-month murder trial that ended in November 2004, prosecutors described Scott as a man who regretted that he was soon to become a father and committed murder to get out of his marriage without having to pay spousal and child support.

“That is so offensive and so disgusting,” he says about the prosecution’s allegations. “I certainly regret cheating on Laci, absolutely. It was about a childish lack of self-esteem, selfish me traveling somewhere, lonely that night because I wasn’t at home. Someone makes you feel good because they want to have sex with you.”

Today, as the L.A. Innocence Project’s appeal of Scott’s conviction makes its way through California courts, Face to Face director Shareen Anderson — who spent a year interviewing Scott via video from prison — says the inmate is “optimistic and confident” that ongoing efforts to free him will be successful.

On May 29, a judge approved his attorneys’ request to conduct a DNA test on duct tape found attached to Laci’s body but refused testing on 16 other pieces of evidence. Scott, however, is patient.

“People want the answer they believed in to continue to be the answer,” he says with a cool smile. “We’re all slow to admit when we’re wrong.”

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