'Paradise Lost 3: Purgatory': Filmmakers Tell Of West Memphis Three's Journey To Freedom (VIDEO)

After serving more than 18 years in prison for the murders of three boys in West Memphis, Ark., Damien Echols, Jason Baldwin and Jessie Misskelley Jr. -- known as the West Memphis Three -- walked free last August.

The three men were allowed to plead guilty to the 1993 murders, and at the same time maintain their innocence, as part of the Alford Plea deal that ultimately set them free.

Filmmakers Joe Berlinger and Bruce Sinofsky chronicled the West Memphis Three's 1993 arrests and their sentencing, despite a lack of physical evidence tying them to the murders, in the 1996 HBO film, "Paradise Lost: The Child Murders at Robin Hood Hills" and a 2000 sequel.

Berlinger and Sinofsky didn't intend to make a documentary about the Arkansas judicial system. They intended to make a film about the murders of Stevie Branch, Michael Moore and Christopher Byers and their convicted killers. "The media was telling a very different story back then, one of guilty teenagers," Berlinger said.

"That's the beauty of this journey is that we went down thinking the opposite because we were being saturated with media that was saying something that ultimately wasn't true," he added.

"After we met these guys -- and it took us a few months to negotiate access to them -- they seemed so credible," Berlinger said. "We just walked away from those interviews feeling like something was wrong. But we were naive enough to think that it was all going to work itself out at the trial. We had no idea that we were going to sit and witness a modern-day witch hunt."

"Why does it take three well-funded HBO documentaries over 18 years and millions of dollars from a vast array of celebrities and regular people agitating to give these guys the kind of defense that they deserved back in '93? There's something wrong with the justice system," Berlinger said, while promoting the third film in the trilogy, "Paradise Lost 3: Purgatory," which premieres Thursday.

"In this particular case, there was a fluke," he said. "The filmmakers came, but there are hundreds of cases where people claim to be innocent."

"We're really lucky that, through HBO ... this case was brought to us, and we went down there open-eyed," Sinofsky said.

Even though the West Memphis Three were released from prison, "Paradise Lost 3: Purgatory" does not have a happy ending. One of the murdered boys' fathers, Todd Moore, is still convinced the three are guilty. Moore wrote a letter to the Academy of Motion Picture Arts and Sciences demanding that the documentary be excluded from Oscar consideration.

HuffPost TV has two exclusive clips from the latest installment of the groundbreaking documentary series.

In the first clip below, Echols, who was initially sentenced to death, talks about having to block out rumors and forget where he was.

The second clip features Misskelley Jr., who was sentenced to life without parole, talking to his attorney and obtaining advice about what to do at an upcoming hearing.

“Paradise Lost 3: Purgatory,” premieres Thursday at 9 p.m. on HBO.