Whether you followed the 1990s case of brothers Lyle and Erik Menendez who killed their parents or simply read about it online, you know how the story ends. The boys, who were defended by Leslie Abramson, were sentenced to life in prison without the possibility of parole in 1996. Now “Law & Order True Crime: The Menendez Murders,” the first ripped from the headlines version of NBC’s true crime franchise, sets out to humanize them.

“It’s not the ‘who’,” said executive producer Dick Wolf at the Paley Center for Media’s Fall TV Preview for his new series. “At the end of the eight hours, you’re going to really understand the ‘why’.”

The show recounts Lyle and Erik’s side of the story (played by Miles Gaston Villanueva and Gus Halper, respectively), but it does not do so linearly. The premiere episode opens with the murders, and then shows what came after the infamous 911 call where they pretended to stumble upon their dead parents and flashes back to life under father Jose’s (Carlos Gomez) roof.

“The idea was to get to know the kids but also to steer into what everybody knew and basically throw up all the negatives that people knew about them, and then in the second and third and fourth episode, you start peeling back,” executive producer Rene Balcer tells Variety. “Yeah, they spent money, but they didn’t spend any more money after the killings than they did before. All of the assumptions we made sort of get turned inside out.”

In peeling back the layers of the brothers over time, the show eases the audience into the allegations of abuse that eventually became Lyle and Erik’s motive. The show starts with some of the emotional and verbal abuse, such as showing Jose quizzing his sons at a family dinner and then berating his youngest for the way he eats, but will eventually move into the controversial physical and sexual abuse allegations as well.

“You get the ‘why’ a little bit on every page of every script,” Villanueva says. “You get to understand the trauma they experienced and the abuse of young kids all the way through, for Erik, a few weeks before the murders. There’s a lot we’re going to show the audience that propelled them.”

In showing the brothers’ side to the story, the producers and cast all feel the show will give the audience a new ability to find empathy in the characters. “Regardless of what they’re accused of, they’re human,” says Edie Falco, who plays Abramson.

For both Villanueva and Halper, they had to find that empathy in order to be able to take on the roles. “No one does things without a reason,” says Halper. “You can agree with it or not, but there’s always a reason, and at the end of the day, what your job is as an actor is to figure out that reason and internalize it.”

As Falco says, “The whole thing is tragic…I have no idea where people will land in regards to this. I think some might be uncomfortable because they don’t like to live in the gray area, and this show is being somewhat bipartisan. But when being presented with all of this new stuff, there’s no way you can’t say, ‘What the hell happened here?'”

The show introduces her at home and through another case, to showcase her passion and lack of concern for what people thought of her – the very traits that drove her to take on the case to begin with.

“We wanted to make her available to the audience, make her alive, set up certain things that are going on in her life,” Balcer says, explaining that when you have an actress like Falco, you don’t wait to put her on-screen. “You have this very dysfunctional family in the Menendez family, and then you have her trying to rectify and deal with issues in her own family as she’s trying to adopt a kid. She thinks those boys did it, but she thinks there’s probably a big tragedy behind it – a family secret that needs to be uncovered. Because that’s been her experience.”

The show also explores the family dynamic of Dr. Jerome Oziel (Josh Charles) and his mistress Judalon Smith (Heather Graham), who exposed the brothers’ taped confession. “It’s a super interesting side plot that is very interesting,” Graham says. “She was very scared because Jerome told her that they would kill her, and she believed him, but she thought she’d be safer if she told the police. So she knew these people killed their parents, and she went and told the police, as I think anyone would.”

From the start, Jose is painted as a narcissist philanderer who drove his wife (Lolita Davidovich) into a depression. But just like Villanueva and Halper wanted to understand their characters, so too did Gomez have to find the man behind the monster. “He was an immigrant who rose to esteem and became a very big businessman. He was a tough guy – a tough businessman and tough on his kids,” Gomez says. “He did love his kids — everyone who saw the family said he loved his kids — but they were out of control. Even before they murdered, they were robbing houses and doing other bad things.”

Even though the show uses flashbacks from different characters’ points of views to give glimpses into the family’s home life, the research used all came from court documents, police reports and newspaper articles from the investigation. Cast members were not encouraged to talk to the real-life people they were portraying.

“I didn’t want to talk to Erik or Lyle because they’re no longer the same young men that they were back then,” Balcer admits. “I wanted to keep that voice unencumbered by my impressions of them now after having been institutionalized for 25 years. But the research is pretty extensive, and I have to say ‘spoiler alert’ for the last episode, because there are two things that you find out that are kind of shocking. When you think about it, they’ll make sense, but they were not known at the time.”

“Law & Order True Crime: The Menendez Murders” premieres on NBC Sept. 26 at 10 p.m.