West of Memphis

In 1993, the bodies of three young children were discovered in a drainage canal in the less than salubrious borough of West Memphis, Arkansas. The boys had been hog-tied and mutilated, a grisly crime that would attract Big Media and widespread speculation.

Within a month, suspicion fell on three local teenagers: Jessie Misskelley, Jr, 17; Jason Baldwin, 16, and Damien Echols, 18. For a bible-belt community acting in the fug of the "Satanic Panic", these boys were a triple threat: they read novels by Stephen King, they listened to heavy metal music, they wore black T-shirts.

Their subsequent trial gave special place to sensational “expert testimony” on ritualistic satanic killings and to a confession wheedled out of Jessie Misskelley, a boy considered “borderline mentally retarded”, with an IQ of 70. Extracts from the tape soon form a distinctive pattern: the interrogator makes a lurid leading statement; the exhausted, non-committal reply comes – “uh huh” or “yes sir”.

The Memphis Three – as they came to be known – have long been a cause célèbre among folks such as Eddie Vedder, Johnny Depp and Patti Smith, all of whom appear in Amy Berg's gripping new film about the case. Lord of the Rings director Peter Jackson, who produced (and appears in) West of Memphis , has also contributed heavily to rolling legal appeals.

In 1996, Joe Berlinger and Bruce Sinofsky – the film-makers behind Some Kind of Monster – made Paradise Lost , the first of a trilogy of campaigning documentaries. Throughout these films – Paradise Lost: The Child Murders at Robin Hood Hills , Paradise Lost 2: Revelations and Paradise Lost 3: Purgato ry – Berlinger and Sinofsky have systematically demolished the prosecution's case.

What could Ms Berg's film have to say that hasn't been said before? Quite a bit, as it happens. Berg, the superb chronicler behind 2006's Deliver Us From Evil , condenses a vast, sprawling travesty of justice into a taut dramatic narrative without ever losing sight of the three innocent men who spent 20 years behind bars.

Beyond reasonable doubt isn’t far enough for the filmmaker: she knows the three boys didn’t do it but she thinks she knows who did.

With echoes of Errol Morris's The Thin Blue Line , West of Memphis transforms a tragedy into compelling, three-act work of advocacy. The film is so utterly transfixing you won't believe almost two-and-a-half hours have passed when the final credits roll.