Peter Jackson had big box-office success over the holidays with "The Hobbit: an Unexpected Journey," part one of his "Lord of the Rings" prelude.

With the magnificent documentary "West of Memphis," Jackson reveals the results of his own unexpected journey, from New Zealand to rural Arkansas, where he and an unwavering band of filmmakers, artists and other dissenters challenged the judicial system and won.

The case of the West Memphis Three - Damien Echols, Jason Baldwin and Jessie Misskelley, imprisoned as teens in the 1993 murders of three Cub Scouts - has become widely known through the activism of actors and musicians who took up the cause, along with three "Paradise Lost" documentaries that called the convictions into question. After seeing that first "Paradise Lost" film in 2005, Jackson and his wife, Fran Walsh, stepped in, financing their own investigation.

"West of Memphis" is nonfiction filmmaking at its best, a film with a fierce point of view yet one that doesn't pretend to have all the answers or a monopoly on truth.

The case shocked the people of West Memphis, Ark., where 8-year-olds Michael Moore, Steven Branch and Christopher Byers were found naked and hogtied in a ditch.

The suspects were convicted in part on a confession Misskelley later recanted, one filled with conflicting details that critics claim was coaxed and prodded by police interrogators. Baldwin and Misskelley were sentenced to life in prison, while Echols was condemned to death.

After Joe Berlinger and Bruce Sinofsky's 1996 documentary "Paradise Lost: The Child Murders at Robin Hood Hills" questioned the prosecution's case, activists rallied around the suspects. A woman named Lorri Davis began corresponding with Echols, taking the lead in the case and marrying him.

Along with Jackson, interviewed extensively in the documentary, and Walsh, Davis and Echols serve as producers on "West of Memphis," creating an unusual scenario in which filmmakers are part of their own story, with a stake in the outcome.

"West of Memphis" offers compelling evidence that the stepfather of one of the murdered boys might have killed them, though it's all circumstantial.

After 18 years in prison, Echols, Baldwin and Misskelley were freed in 2011 after entering guilty pleas that allowed them technically to maintain their innocence. It's a triumphant moment in "West of Memphis." And like many great dramas, it's an ending that satisfies but also vexes, because the story really isn't over.

If you believe Echols, Baldwin and Misskelley murdered those boys, then child killers now are out on the street. If you believe they didn't do it, then innocent men spent half of their lives in prison, while someone else got away with murder.