Sheen, who helped shop the project, will also serve as the narrator on the docuseries that will premiere early next year.

Television's fascination with the O.J. Simpson trial is adding a third series.

Martin Sheen will executive produce Hard Evidence: O.J. Is Innocent, a new true-crime docuseries that will attempt to show that Simpson is innocent.

In a competitive move, Investigation Discovery — the cable network known for its crime, mystery and documentary programs — has picked up the six-part entry that will reinvestigate the Simpson case from beginning to end.

The show will reveal critical new evidence in the slayings of Nicole Brown Simpson and Ronald Goldman, as well as unveil an entirely new hypothesis for what happened in Brentwood 20 years ago. While Simpson was acquitted in the so-called "Trial of the Century," he was found liable in a civil suit two years later, and questions about his role in the slayings remain widespread.

In addition to exec producing, Sheen will narrate the series. (An existing contract with Netflix for scripted comedy Grace and Frankie prohibits him from appearing onscreen elsewhere.) Hard Evidence will largely be based on more than two decades of dogged legwork by Texas private investigator William C. Dear, whose book, O.J. Is Innocent and I Can Prove It, presents “never-before seen evidence” and a compelling alternative theory in a case most people have long thought resolved.

Investigation Discovery landed the project following a multiple-network bidding war that counted players including Amazon over the past two months. “All of the major players were looking,” says ID Group president Henry Schleiff, who noted other bidders included premium cable. Objective Media Group America/All3Media America will produce, with Jimmy Fox, Greg Lipstone and Layla Smith set to exec produce alongside Sheen and Dear.

Martin Sheen is represented by ICM Partners. Objective/All3Media is represented by ICM Partners and Hansen, Jacobson, Teller, Hoberman, Newman, Warren, Richman, Rush & Kaller, L.L.P. Bill Dear is represented by ICM Partners, Sally C. Helppie, Esq. and Vincent Serafino Geary Waddell Jenevein, P.C.

Schleiff, who used to work at Court TV (sometimes mockingly referred to as the “O.J. Network” during the trial) knew Simpson and yet, like most people, believed the former NFL Hall of Famer was guilty, despite an acquittal in his criminal trial. But when Dear presented Schleiff with examples of evidence he had uncovered during his 20-year “obsession” with the case — including a knife the investigator believes is the actual murder weapon, medical and forensic reports and a trove of other physical material the investigator claims LAPD never examined — Schleiff says he was forced to reassess.

“Like most others I had always believed that the evidence showed that [O.J.] did it,” Schleiff says, “I went into this with a tremendous amount of doubt and cynicism, but this is so amazingly convincing that when you do connect the dots and look at the new evidence, it made me accept the fact that O.J. could actually be innocent.”

Sheen noted he hoped the series will help answer three central questions: “What if there were enough evidence that proved O.J. Simpson did not murder his ex-wife Nicole or Ron Goldman? What if the real killer were still at large? And finally, what if a grand jury convened to reconsider the case based on new evidence?”

After 20 years of relative quiet, interest in the Simpson case has reached new peaks of late with FX critical darling The People v. O.J. Simpson: The American Crime Story. This summer, ESPN will air its five-part docuseries O.J.: Made in America.

And interest in the case continues beyond the small screen, when excitement reached a fever pitch this month when the LAPD announced that a knife had been discovered on Simpson’s now-demolished property and that it was never disclosed to police. It has since prompted renewed speculation about the murder weapon. The knife was soon found to be unrelated to the slayings of Simpson and Goldman. Inside Edition, meanwhile, recently tracked down the whereabouts of the iconic white Bronco, which O.J. rode into infamy in perhaps the most famous car chase of the 20th century. Former O.J. associate Michael Gilbert is storing it in his garage in central California.

Dear and Sheen have been working together for more than a year, honing their pitch, and the pair recently began shopping the idea around Hollywood as The Hollywood Reporter exclusively reported last month. Interest was immediate and intense, people familiar with the deal say. The two met through the actor’s son, Charlie Sheen, who invited Dear out to Los Angeles several years ago to speak to a private audience about his work on the Simpson case.

For his part, Dear has high hopes for what the series will deliver. “I’m hoping that when we do this series, the evidence should be more than enough to get a grand jury indictment,” he tells THR. “If I accomplish that, I will have accomplished a great deal in my life. I’ve done the best I can and I’m excited about the fact that finally I can get it out there.”

While there’s no production schedule yet, ID plans to air the series in the first quarter of 2017. Network execs declined comment on the sale price, but Schleiff acknowledged that they weren’t going to skimp on producing Hard Evidence.

“To do it correctly, to go on location, to interview all the people in what is essentially a brand-new story means it’s expensive,” he says. “The viewer may agree or disagree with the evidence, or the point of this series, but it raises very legitimate questions, and that’s what we’re in the business of doing.”