The fourth documentary to examine the railroaded conviction of the West Memphis Three for the 1993 murder of three young boys, West of Memphis is more a work of advocacy than of journalism. As such, it has been uncommonly effective. In 2011, its investigation, funded by Peter Jackson and Fran Walsh, into the wrongful conviction and incarceration of Damien Echols, Jessie Misskelley, and Jason Baldwin actually led to the release of these three young men, who had spent the past 18 years in prison. That makes this the most rare of films: one that indisputably matters. And one that stuns, and not in the way that film reviewers who like to get quoted in ads so often misapply that word. This is a movie that can stun you. Exhausting, thorough, and sharply crafted, Amy Berg's doc covers the saga in its entirety. The crime-scene photos are harrowing, the prosecution's dishonesty is enraging, and the long wait for justice to get around to righting things is agonizing. Especially upsetting are scenes involving John Mark Byers and Terry Hobbs, an adoptive father and stepfather to the murdered boys. Byers fulminated against the West Memphis Three for years and then found himself accused of the crime; still, he seems not to have learned his lesson and now shouts "child killer" at Hobbs. Hobbs, meanwhile, becomes the focus of the multimillion dollar investigation funded by Jackson and company. In video of a deposition in a bullshit case Hobbs filed against a Dixie Chick, Hobbs is hit with questions about his history of violence, and we watch this tight-lipped, poker-faced man realize that he's overmatched and then swallow back rage as he's made to account, publicly, for the darkest moments of his life.