Lyle Menendez on ‘Skepticism’ of His Sexual Abuse Claims — Which Prosecutors Call an ‘Excuse’

On a recent Sunday morning, Lyle Menendez sat in the day room at California’s Mule Creek State Prison quietly talking on the phone about his dad Jose and mom Kitty, who he and his younger brother, Erik, brutally murdered with two 12-gauge shotguns nearly three decades ago.

“I’ve sort of made peace with who my father was,” Lyle tells PEOPLE in a rare prison interview that appears in this week’s issue, on newsstands now.

“He had a sickness and I’ve forgiven him,” Lyle says, “but I don’t know if he’s forgiven me.”

The 49-year-old convict — who along with his brother was sentenced to life in prison without the possibility of parole for the grisly killings of their wealthy parents in 1989 — pauses for a moment as he speaks, then continues: “I don’t know if my mother forgives me, but I have definitely struggled mightily to find a peaceful place to forgive her.”

Exactly why Lyle feels the need to forgive the two people he and his brother shot 15 times, as they watched TV in the den of their Beverly Hills, California, home, lies at the heart of what made the case one of the nation’s most-publicized.

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The killings, the brothers and their attorneys claimed at trial, were done in self-defense after years of sexual abuse by their entertainment executive father — abuse they insisted was ignored by their stay-at-home mom.

It’s a claim that Lyle continues to make, long after he was dismissed by investigators. He describes the murders to PEOPLE as “the most astounding and regrettable thing that has happened in my life.”

‘This Was All About Money’

Plenty of people don’t buy the brothers’ story. “Lyle is a congenital, pathological liar,” says retired Los Angeles County Deputy District Attorney Pam Bozanich, the prosecutor for the first trial, which lasted six months and ended in two hung juries. (Each brother had a separate jury.)

“The only way that they could go to trial and have any hope of not getting the death penalty was to make up an abuse excuse,” Bozanich says of the brothers, adding, “This was all about money. And I was very convinced by the end of the trial that the whole thing was fabricated based upon evidence that I gathered from various sources.”

Instead, prosecutors argued, the brothers’ motive was purely financial. After their parents were killed and before their arrests, Erik and Lyle went on a lavish spending spree.

Lyle — who claims his father sexually abused him between the ages of 6 and 8 and continued to molest his brother up until his murder — knows his allegations have been dismissed by many.

“There’s always going to be skepticism,” he says. “People think I just hopped up on the witness stand and told a story that a sleazy defense attorney made up. But many people knew there was sexual abuse in this family.”

One of those believers is a relative: Kitty’s eldest sister, Joan Vander Molen.

“I loved my sister very much and have been so very sorry that she was not strong enough to take care of her children when they needed her protection,” Vander Molen tells PEOPLE.

“Kitty must have felt tremendous shame and guilt knowing her husband’s sexual dysfunction went beyond affairs. … Our family tragedy should be a lesson to all on the destructive effects of child abuse and molestation, whether they are wealthy or not.”

During his two murder trials in the mid-1990s, Lyle claims that he and his brother received “thousands” of letters from those touched by their accusations of abuse — and people often wrote about their own poignant experiences.

‘I Was My Father’s Prized Son’

For the past 15 years Lyle has served as president of the inmate government, but three years ago — in an attempt to find what he calls the “meaning beyond the tragedy” — he organized an informal support group for inmates whose lives were derailed by childhood sex abuse.

He says he is working with prison officials, doctors and a handful of researchers to create a more “structured curriculum,” involving upwards of 40 inmates.

“The purpose is not therapy,” Lyle says. “The purpose is getting the weight of keeping it a secret off the shoulders of these guys, allowing them to realize that bottling this up has caused many of the problems that got them here.”

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Renewed attention over the brothers’ case (thanks mostly to Lyle’s speaking-out from behind bars) has prompted Lyle, through the help of family members, to create a Facebook page dealing with child sex abuse.

After nearly 27 years behind bars, he says he regrets that fateful night in August 1989, when he and Erik killed their parents in a rampage.

“I was my father’s prized son,” Lyle explains, before claiming, “At the same time I had been very brutalized by him and keeping his secret was a part of who I was.”

He continues, “What I regret is not having our family somehow get this secret out earlier and maybe it could have been resolved without this tragedy and destruction. The explosion that occurred that weekend shattered and destroyed everyone’s lives.”