While difficult to sit through, West Of Memphis, a documentary on the murder of three eight-year-old boys in Arkansas, 1993 is unmissable.

In 1993 the bodies of three boys were discovered naked, hogtied and with visible marks of torture and sexual mutilation on their bodies. Three teenagers are arrested - Echols, Baldwin and Misskelly - with the confession of the latter, a boy with learning difficulties, being the nail in the coffin. 'Ringleader' Echols is given the death sentence with Baldwin and Misskelly receiving life. However, new evidence comes to light that proves the boys' innocence and celebrities like Eddie Vedder, Johnny Depp, Henry Rollins and Peter Jackson, who also produces the film, throw their weight behind their release.

Although covered in more detail in Joe Berlinger and Bruce Sinofsky's Paradise Lost trilogy (1996 - 2011), West of Memphis's not-too-shabby two-and-a-half hours running time covers enough to make it more than just a recap. The framing of the documentary is this terrible miscarriage of justice, but also police incompetence and coercion. Witnesses for the prosecution are deemed 'experts' in their field despite being far from it; with tensions running high the bible belt area accept the prosecution's satanic ritual angle ("the horrific injuries warped people's judgement") but the worst is left to the judge. When presented with new DNA evidence and the recantation of testimonies years later the Judge David Burnett, eyeing a political career, dismisses the idea of a new trial. It's one of the many moments here that you stare at the screen in disbelief but, as a well-spoken Echols points out, "this case is nothing out of the ordinary." Scary that.

Unlike the recent The Imposter, which raised the notion that the missing child was killed by a family member but then didn't delve into it, West of Memphis devotes a large part to the possibility that the guilty party is one of the boy's step fathers. However, director Amy Berg, who takes more of a backseat than she did in her equally difficult Deliver Us From Evil, seems as convinced of his guilt as the original jury was of the three teenagers.

West Of Memphis can be a hard slog but as documentaries go it's tough to top this year. Based on these events, The Devil's Knot, starring Colin Firth, will be released later this year.