A Los Angeles prosecutor said on Thursday he is asking the court to re-sentence Erik and Lyle Menendez after they have spent more than 30 years in prison for the shotgun murder of their parents, after new evidence emerged indicating they were sexually abused by their father for years.

The recommendation raises the possibility that the brothers will be released on parole.

"I believe that under the law, resentencing is appropriate and I am going to recommend that to a court tomorrow," Los Angeles County District Attorney George Gascón told a news conference.

Gascón said he would recommend that their life sentences be removed and replaced with a sentence of 50 years to life, but that they would be eligible for parole because of their young age at the time of the murders.

"I believe they have paid their debt to society," Gascón said.

The Menendez brothers, now 56 and 53, were convicted after the second of two highly publicized trials that captivated the United States at the time because of their wealth and privilege as the sons of a record company and entertainment industry executive.

Jose Menendez was shot in the back of the head and Kitty Menendez was shot 15 times at their Beverly Hills home. Lyle was 21 and Erik was 18 at the time.

Months of talks between prosecutors, defence

A recent Netflix series dramatizing their story revived interest in the case, but for more than a year defence lawyers have been in talks with prosecutors about vacating the sentence or seeking a new trial, citing new evidence that came to light supporting the brothers' claim they had been molested for years.

In their first trial, which was televised and ended in a hung jury, the brothers testified they were sexually mistreated by both parents for years and were acting in self defence, and that their father threatened to kill them if they revealed the abuse.

Prosecutors argued the pair were seeking their parents' multimillion-dollar fortune.

A jury convicted them in a second trial in Los Angeles County Superior Court that was not televised, but that same jury also spared them the death penalty, opting for life in prison without parole.

Gascón has said there is no doubt the brothers killed their parents, but cited new evidence, including a letter Erik Menendez purportedly wrote to a cousin eight months before the murders in which he described the abuse. Had the evidence been presented at trial, the jury may have reached a different outcome, he said.

Investigators also are examining allegations from a member of the 1980s pop band Menudo who said he was abused by Jose Menendez. Those allegations were publicized last year in Peacock documentary series called Menendez + Menudo: Boys Betrayed.

Gascón also said he was concerned by comments from a member of the prosecution team at the time that men could not be raped. "Our office has developed a more modern understanding of sexual violence since the Menendez brothers first faced prosecution," Gascón said in an Oct. 16 statement.

DA's election challenger questions timing

Gascón previously said he would wait until a Nov. 26 court hearing to made a decision on the case, but he sped up the decision given the intense public interest.

He also faces a difficult re-election battle against challenger Nathan Hochman on Nov. 5.

Hochman on Thursday questioned the timing of Gascón's announcement, coming less than two weeks before the election and calling it a "desperate political move."

He said he is unable to form his own opinion on the case without access to confidential records and relevant witnesses.

"If I become D.A. and the case is still pending at that time, I will conduct a review consistent with how I would review any case," Hochman said.