A California man famously convicted of murdering his pregnant wife has spoken out for the first time in 20 years.

Scott Peterson, now 51, killed his wife Laci Peterson when she was eight months pregnant with their son in 2002. He had been married to Laci for five years when she disappeared on December 24, 2002, after taking their dog for a walk.

Peterson said from jail that he remembers his wife's 'smile' on the day she disappeared. He also said that he regrets not testifying at his trial.

'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 convicted killer said.

Laci, 27, was eight months pregnant with their first child when she went missing. Her remains as well as the fetus of her unborn son - who the couple had named Conner - were found in different locations in the San Francisco Bay over three months later.

Since he was arrested and convicted of double homicide over two decades ago - Peterson has never spoken out. The cause of death was never determined - as Laci's corpse was in a bad state when it was found washed ashore on April 14, 2003. 

However, he broke his silence on the murder from Mule Creek State Prison in California in an interview conducted over video call for a Peacock documentary.

Peterson discussed the details of the final hours before his wife 'vanished' and the things he would 'relish' about that 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 in the documentary: Face to Face with Scott Peterson. 

Peterson, who formerly worked as a fertilizer salesperson, is now serving a life sentence without the possibility of parole.

He still denies any involvement in Laci's disappearance or the death of her and their unborn child. 

Peterson agreed to the documentary to appeal to the public and further claim his innocence.

The convicted killer wants to share his side of the story and the 'so-called investigation,' as he refers to it. 

He claims officers and prosecutors ignored significant leads and relied on circumstantial evidence to make their case during the 2004 trial.

'I regret not testifying [at my trial],' he says. '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.' 

Peterson also broke his silence on his extramarital affair in the documentary.  

There was a third person involved in their marriage in 2002 - a woman who became a critical part of detectives' case against the keen golfer and dad-to-be.

Amber Frey, now 49, was unknowingly Scott's mistress for weeks before he killed his heavily-pregnant wife Laci - and she cunningly kept her relationship going while helping police nail Peterson as the suspect in the chilling murder case. 

Now, a trove of their intimate phone conversations have been made public.  

Frey, who was a single mom to her young daughter at the time, revealed that she had just finished school in California when one of her friends told her that there was this 'handsome guy' who was looking to 'meet the one,' and introduced her to Peterson. 

Speaking on Netflix's new series 'American Murder: Laci Peterson,' Amber said of her blossoming new relationship with Scott: 'We started talking on the phone. 

'I thought he was handsome, he had a really nice smile, he had a good head on his shoulders. He was interested in my life and my daughter, and he was sweet with her.

'We laughed a lot, we had some good conversations.'

During their courtship, which she said started around November 2002, Amber asked Scott if he had ever been married - and he said no.

In the new trailer for the docuseries, the detective on the case, Jon Buehler, suggested Peterson committed the murders because he 'didn't want to pay child support, didn't want to pay spousal [support] and this is the way he thought about getting out of it.'

Peterson is currently seeking retrial for his wife and unborn son's deaths and his case is being re-examined by the Los Angeles Innocence Project.

Laci's disappearance was first reported by her husband, who initially claimed he had been out golfing, when he returned to their Modesto, California home to find it empty and their dog running around the backyard dragging its leash.

However, Peterson told his neighbor a different story, claiming he was fishing 90 miles away on his recently purchased boat out of Berkeley Marina.

He reported Laci missing to police and called his mother-in-law to tell her that his pregnant wife was nowhere to be found.