The setting for the grisly double murder could not have been more incongruous: a balmy August evening in the exclusive enclave of Beverly Hills.

José and Kitty Menendez – he a successful music industry executive, she a local socialite and former beauty queen – were blasted to death in a hail of bullets as they watched television in the den of their palatial family mansion.

Such was the horror of the scene that police first thought it must be an underworld hit, somehow connected to a business deal gone wrong.

Indeed, as former Beverly Hills Detective Sergeant Tom Edmonds, who investigated the murders and was at the scene that night in 1989, told me last week: ‘It was very nasty… blood, gore and bits of bodies everywhere.’

But rather than mobsters, seven months later it was the couple’s sons Lyle, 21, and 18-year-old Erik – handsome, well-mannered and precociously talented tennis players –who were arrested.

Police suspicions had been ignited after the brothers embarked on an almighty $1 million spending spree after their parents’ deaths, buying a Rolex, a Porsche and even a restaurant.

When it emerged in March 1990 that Erik had confessed all to his therapist, the authorities pounced – and the boys admitted they had killed their father and mother.

Yet this seemingly cut-and-dried case of privileged boys who murdered their parents continues to captivate millions and divide opinion 35 years on.

Indeed, September saw the launch of a Netflix drama series called Monsters: The Lyle And Erik Menendez Story, featuring A-list actors Javier Bardem and Chloe Sevigny as Jose and Kitty, revisiting the gruesome killings that captivated America.

For there were two knife-edge trials, the first of which was televised in 1993 and made dark allegations of psychological and sexual abuse inflicted on the brothers by a sadistic father, with the knowledge of an unloving mother.

Then, after a hung jury and amid wall-to-wall media coverage, the pair were convicted of first-degree murder in 1995, and sentenced to life imprisonment without parole.

Now, the Mail has spoken exclusively to people intimately acquainted with the case – including one who claims to have new evidence that could lead to the pair’s release – to get to the bottom of the tantalising question: did the brothers kill to get their hands on the family’s $14 million fortune or were they victims, driven to the edge after years of abuse?

Many remain convinced Erik and Lyle, now aged 56 and 53, are cold-blooded killers who should never be released.

Yet a growing number of supporters believe the siblings’ trial was unfair and, as they put it, the ‘abuse excuse’ should have led to more lenient prison terms.

One of these is Robert Rand, an Emmy-award-winning writer and author of the newly updated Menendez Murders, who has campaigned tirelessly on the brothers’ behalf and visits them in prison.

‘The number one question people ask me is why didn’t Lyle and Erik just walk out of the door. But their parents were controlling every aspect of their lives, and the abuse started when they were very young,’ says Rand when we meet in Los Angeles.

‘The brothers weren’t thinking or reacting like normal people. If the Menendez trials were heard today, I think there would be a different ending because there is much more understanding of abuse and violence within families than there was.’

Ten days prior to the murders, Rand, a reporter, had briefly met Jose at a video industry convention in Las Vegas.

‘We shook hands, spoke for a few minutes and he couldn’t have been nicer – he seemed like a great guy,’ he recalls.

Then, on the evening of August 20, 1989, police received a call from the Menendez brothers. They claimed to have arrived home from a night out, to have found their parents shot dead, with such terrible injuries, they were barely identifiable.

José had taken six bullets, including a fatal shot to the back of the head. Kitty, meanwhile, had been shot ten times.

The next day, a colleague called Rand, reporting that the businessman and his wife had been killed in a shooting believed to be a mob hit, related to the video distribution business.

Rand was assigned to write an article for the Miami Herald magazine about the mysterious murders.

A few weeks later, he interviewed the orphaned Lyle and Erik, meeting them at the very mansion which had seen such carnage.

Rand says he felt a chill when he walked by the open doors of the den where the slaughter took place.

While the room had been cleaned and was empty of furniture, he thought it strange the brothers weren’t avoiding the room – and, moreover, that they were living in the mansion at all.

‘When I met them, I had no reason to be suspicious,’ Rand tells me. ‘They talked about what a terrible loss it [the death of their parents] was and spoke admiringly of their father.’

Police, too, initially had no reason to suspect the boys and, crucially, did not interrogate them as suspects that first night or give them gunshot residue tests which might have shown they had handled guns.

It was Erik and Lyle who suggested the deaths were an underworld hit, Detective Sergeant Tom Edmonds tells me.

Police thought this was credible since 45-year-old José had recently purchased a video company producing pornography for the mafia, with the intention of using the recording equipment in the music business.

However, that theory fell by the wayside after Edmonds visited a noted mafioso receiving medical treatment in a New Jersey hospital who told the detective there had been no problem with the business deal.

‘The mafia guy was frank… He said “If we’d done it, we wouldn’t have killed the wife and it wouldn’t have been so messy”,’ says Edmonds.

Yet the brothers, obviously desperate for another suspect to detract from their own guilt, wouldn’t let go of the Mafia theory.

Rand’s alarm bells began to ring when one of the boys’ relatives told him Erik and Lyle were receiving death threats, which they thought were from the Mob. ‘When I called the police to ask about this, they said “What death threats?”’

Perplexed by the brothers’ untruths, Rand wrote an article, which was the first to speculate that the brothers’ stories didn’t add up.

He says he wasn’t surprised when Erik and Lyle were arrested seven months later.

Rand bagged a coveted seat in the courtroom for the first trial in 1993. Each brother had his own own defence team and own jury. The public queued for seats in court from 4am and TV cameras filmed everything; even President Clinton was said to have sneaked away from the Oval Office to catch up on the drama.

The prosecution alleged the boys were spoiled rich kids, murdering their parents to get their hands on the family’s estate.

Lyle and Erik leaving the courtroom in Santa Monica in 1990, after a judge ruled that conversations between the two brothers and their psychologist could be used as evidence in their murder case

Emmy award winning journalist Robert Rand, right, with Lyle Menendez  in prison

Lyle and Erik’s most up-to-date mugshots. The infamous brothers are now 56 and 53 years old

The Beverly Hills mansion at 722 N. Elm Drive where Erik And Lyle Menendez  brutally murdered their parents. The much debated question is why?

Impossibly dark details of the shootings were revealed: Lyle told how, after shooting his father, he noticed his mother, who had already been shot several times, ‘sneaking’ away, crawling round a coffee table. He dashed outside to get more ammunition for his 12-gauge shotgun, sprinted back, reached over the coffee table and fired. The fatal shot, said experts, occurred with the gun muzzle pressed right against her face.

The defence, though, insisted the boys murdered their father only after years of sexual abuse. Their mother, they claimed, knew and did nothing.

The eldest, Lyle, who said he was molested between the ages of six and eight, claimed he confronted his father aged 13 after sensing the same was happening to Erik.

His father, he said, promised to stop but didn’t.

In graphic evidence, Erik said his father forced him to have sex two or three times a month and told him they doing what soldiers did ‘in ancient times, the Romans and the Greeks’.

The audience was divided: sceptics thought the brothers’ tale of abuse appeared rehearsed, while others said it was impossible to conceive that they had concocted such disturbing events.

‘People watched the abuse testimony on television, but it was a much more intense experience to be in the courtroom, 20ft away from the brothers. There was scarcely a dry eye in the courtroom,’ recalls Rand.

Hazel Thornton was a 35-year-old telecoms engineer when she was picked for Erik’s jury, which consisted of six men and six women.

The brothers’ evidence, she said, was compelling. ‘It was never a case about guilt or innocence because they confessed to killing their parents, but about why it happened,’ she tells the Mail.

‘It was about whether they had been raised in such a way as to create the kind of fear that would cause them to suddenly lash out at their abusers. The bottom line for me was… in normal families, people don’t kill each other.’

With a clear divide in the jury room, tensions rose in what Thornton calls a ‘battle of the sexes’.

‘The men were pretty hung up on the sexual abuse and didn’t believe a father would do that to his sons,’ she tells me.

The women jurors thought otherwise, however: ‘We not only thought it was possible they had been sexually abused, but that there were other types of abuse – neglect, mental and emotional abuse, physical abuse.

‘The women were logical in their arguments about why it should be manslaughter and not murder.’

In the event, all six men voted for murder. All six women voted for a manslaughter verdict carrying a lighter sentence.

A retrial was scheduled after the jury deliberating Lyle’s charges was also deadlocked.

The second trial, concluding in 1996, found both brothers guilty of first-degree murder.

But Rand says this second, untelevised trial started against the backdrop of prosecutors losing a string of important cases, including the politically fraught Rodney King police assault trial and the notorious OJ Simpson trial.

‘The LA County District Attorney’s office was determined to win a high-profile case at any cost… the judge kicked the TV cameras out of the courtroom and didn’t allow the defence to present the family history that had been the heart of the first trial,’ he claims.

Detective Sergeant Edmonds, now 86, says he believes it was the right verdict, and dismisses Rand and other supporters of the convicted killers as ‘mis-informed do-gooders’.

‘The sexual abuse defence came out of nowhere and was completely fabricated,’ he tells the Mail. ‘In effect, they murdered their mother and father twice because they blackened their parents’ reputation.

‘Those kids should have got Academy awards because they were such good actors in the witness box.’

So much so that, at first, he says, he even was taken in. On arriving at the murder scene that night, he remembers ‘their distress appeared genuine’.

But he says their later behaviour made him think again: ‘After their parents’ funerals, those boys started spending money like drunken sailors and living the lifestyle of millionaires, right off the bat.’

Crucially, for those who say it was murder not manslaughter, Edmonds sees planning and intent: ‘They picked up the expended cartridges, got rid of the guns and we never found the clothing they were wearing that night.’

Rand, however, says his dogged investigative work over nearly four decades has uncovered possible new evidence: a letter only found in storage in 2018, and therefore not presented at either trial.

It reveals that in December 1988 – nine months before Erik and Lyle killed their parents – Erik, then 17, told his 15-year-old cousin, Andy Cano, about the ongoing abuse by his father.

‘I’ve been trying to avoid Dad … I never know when it’s going to happen and it’s driving me crazy,’ the youngest Menendez sibling wrote about his father’s alleged assaults.

Rand also uncovered claims about Jose’s predatory sexual behaviour made by Roy Rossello, a former member of the Puerto Rican boy band Menudo, who had signed to RCA, the record company Jose worked for.

The now 54-year-old Rossello alleges he was given wine to drink and sexually abused on three occasions, including once at the Menendez family home, by José in the mid-80s when he was around 14.

‘Nothing should ever give you a free pass to kill your parents but there were clearly mitigating circumstances in this case. We hope these two new pieces of evidence will lead to a new trial,’ says the writer.

The trial was told Kitty (Chloe Sevigny) knew about sexual abuse in her family but  largely ignored it

Leading up to explosive scenes at the dinner table, where Jose Menendez  (Javier Bardem) screamed and shouted at his sons

Erik and Lyle (Koch and Chavez) were very close as brothers and devised the murder plan together

Edmonds, though, dismisses this letter, saying that the recipient, Andy, died of a drug overdose and cannot give evidence about its authenticity.

The retired cop also claims he and his colleagues investigated the Menudo allegations.

‘I interviewed Ricky Martin [the Puerto Rican superstar, who was a member of the Menudo band in the 1980s]. He said any claims of that sort are ridiculous. He said the only thing José was interested in was making money.’

The Netflix series suggests that the affluent family concealed shattering secrets.

‘I need to know what’s going on with you and the boys,’ Chloe Sevigny says to her on-screen husband in her role as Kitty. ‘I don’t want there to be any more lies between us. I won’t tell anyone.’

After their conviction, the brothers spent 20 years apart in separate prisons, but are now both at R.J. Donovan State Prison in San Diego, which houses some of America’s most violent criminals.

Both Erik and Lyle married behind bars. Lyle was married to former Playboy model Anna Eriksson from 1996 to 2001, before marrying Rebecca Sneed, a lawyer, in 2003. Erik married Tammi Sackerman, a former prison pen pal, in 1999.

While the brothers are not allowed conjugal visits, their wives visit them often.

The brothers in the Netflix drama, which explores the claims of sexual abuse put forward as a motive for the murders

Jose Menendez was convinced his sons could be world-class tennis stars. Pictured are Chloe Sevigny and Javier Bardem watching a match in the series

Rand also sees the brothers regularly. ‘Their attitude is they’re probably going to spend the rest of their lives in prison so they’re trying to make the best of it,’ he says.

‘Both teach victim impact classes in which people examine the effect of the offences they committed, both counsel other sexual abuse victims and both are studying for college degrees.’

Even behind bars, the brotherly bond remains. Lyle told an interviewer of his brother’s work with inmates who are terminally ill, saying: ‘It’s so amazing to me that you can come from such terrible circumstances and then grow up to be someone who is so empathetic, I’m very proud of him.’

In 2023, the pair’s legal team filed petitions to vacate their sentences saying the new evidence lessens their culpability.

If that happens, there could be a new trial, or the brothers could be released on time served.

If the brothers had received manslaughter charges, says Rand, they would have had maximum sentences of 22 years and be free men by now.

‘Both Erik and Lyle have repeatedly expressed remorse for what they did,’ he tells me. ‘They both wish they could turn the clock back and do things over.’

In the absence of a time machine, however, there’s only one certainty: the debate over the Menendez brothers’ crimes will run and run – whatever the outcome of their latest legal appeal.

Monsters: The Lyle and Erik Menendez Story is out now on Netflix.