Transcript for Marcia Clark says 'The Fix' 'draws on my experiences as defense attorney, prosecutor'
history. Reporter: Had O.J. Been convicted, would your life be different? How could I know? If he had been convicted, maybe I wouldn't have left the office, but maybe I would have. Looking back, you know, I really do think it was a time in my life to do something different. We're here to decide who murdered Ronald Goldman and Nicole brown. Reporter: It's 1995, and Marsha Clark is front and center at the trial of the century. We do have sufficient evidence to find him guilty. Reporter: The lead prosecutor against orenthal James Simpson. In a case closely watched by millions of people around the country. He and Nicole had this incredibly violent relationship. On the particular day in question, many, many things all went wrong for him at the same time and he exploded, which is why we wound up with so much evidence. Reporter: But she had one of the worst trial losses in history. After O.J. Was acquitted, Clark left her trial law career behind, setting off on a path to redefine herself as an author of best-selling novels. I always loved to write. From the time I was a kid, I was always addicted to crime fiction. Reporter: And now her latest You're never going to get me. Reporter: As co-creator of ABC's new legal drama "The fix." How much of it is your origin story? About this much. When you get about three minutes into the show we depart immediately. To the extent it's a prosecutor in Los Angeles who lost a high-profile case, that came out of my life. Why are you doing this? You lost, now you want revenge? You hate me for not suffering enough? Believe me, I have. This isn't personal, Mr. Johnson, it never has been. Reporter: The Tunney is the actress who poses as the attorney. What are you doing here? He did it again. You have to come back, Maya. This time, we're going to get him. Marsha gave me so much rein, and it was clear from the beginning, are you not playing me. We're going a completely different direction. And I think she wanted to write something that was fun, an escapism, a whodunit in a glossy it's designed to be really entertaining. This case is already being tried in the court of public opinion. Reporter: Part fictional legal drama. It's a soapy show. Fast-paced, romance, of course, but there's a lot of bad behavior, people doing unto others a lot. Not guilty. Reporter: And part art imitating life. Did it. Mr. Simpson, orenthal Simpson, he did it. You're never going to get me. I'm an innocent man. Reporter: But Clark insists "The fix" is not a revisionist tale of revenge against O.J. Simpson for that not-guilty verdict heard around the world. The show is not you, but it's you-ish. It draws on my experiences as a defense attorney and prosecutor. Reporter: So is it complete fantasy? Yes, this is really all fiction. It really is all fiction. Even sevi Johnson, he's British. He's not a football player. Very complex character, very compelling character. All of the characters have an art they go through. It's my fantasy in terms of getting to write a project like this. For sure. This is about justice and seeing that justice is done. Reporter: But no matter what, it seems more than two decades later, the O.J. Case continues to follow her. I'm trying to win. Reporter: Spawning a hit mini series, "The people versus O.J. Simpson", and an academy award winning documentary "O.J., made in America." I learned about him about his ability to perform. He knows how to put on an engaging and warm persona. That is not the persona I saw in court. Reporter: Tunney who was in hit shows like "The mentalist." A window was open. Screen outside. The cops think that's how Jefferson broke into the house. Reporter: Lean partly on the character's inspiration. How closely did you work with Marsha on Maya? She was there all the time. I wanted freedom to do things on my own and she was really good about that and create a different back story. If somebody is famous at another job and they work on a TV show, they're working just as an adviser. They're not a creator. Marsha actually wrote this. She was in the room pulling, you know, her sleeves up and getting down and dirty and had like a real writer's room. And she was there, working terrible hours with a lot of pressure. I can't talk to you without your attorney present. Reporter: But unlike Maya in the show, Marsha in real life is perfectly fine with life outside the courtroom. If O.J. Simpson ever did anything again that was horrific or heinous, would you jump back in? I wouldn't be able to jump back in. There's a bit of fantasticalness in the way Maya comes back in, and that's not particularly realistic, and they have a lot of really good prosecutors. They don't need me. Reporter: For "Nightline," I'm Matt Gutman, Los Angeles. And "The fix" airs Monday nights at 10:00, 9:00 central here on ABC.
This transcript has been automatically generated and may not be 100% accurate.