On Friday, April 8, 1994, five days after he disappeared, Kurt Cobain was found by electrician Gary Smith in an apartment above the garage of his Seattle home. By his side were a cigar box of ‘drug paraphernalia’ and the shotgun used to blow the rock star’s head off. These are the facts.

Or rather, Cobain’s death is the fact (no Elvis spotting in his legend), but the circumstances are more open to doubt and conjecture. That’s partially what controversial documentarist Nick Broomfield’s latest is all about. He set out to make a film about Cobain, his music and his inevitable death, but somewhere along the line this BBC-financed picture takes a detour from which it never returns: the drug squalor; the numerous copycat suicides; the internet buzz of conspiracy. And then there is Courtney Love.

Cobain’s wife of two years, mother to his daughter, leader of her own band Hole, and rising actress (she’s rather good in The People Vs Larry Flynt), most of the fingers that point to collusion point at her. And as Broomfield moves between Los Angeles, Seattle and the godforsaken red-neck hole that was Cobain’s hometown of Aberdeen, he collects a gaggle of conspiracists and gainsayers all too free with accusations of everything from neglect to murder.

Or maybe not murder. At least, not on camera. Because, as Broomfield’s commentary makes clear, libel law necessitates some of the more colourful material is excised. Like that of Tom Grant, the private detective Love engaged to find her husband after he absconded from drug treatment just days before his death. Grant works the case full-time now, maintaining an obsessive web-site dedicated to proving murder. And like El Duce, hirsute vocalist with sleaze-rockers The Mentors, who, it’s clear, is claiming Love offered him $50,000 to off hubby. He died shortly after filming, hit by a train.

The triumph of Kurt and Courtney is in the way Broomfield sifts his ‘evidence’. He starts out sceptic, gradually finds himself buying into the myth (why no fingerprints on the gun? who added the last lines of the suicide note? why wasn’t Cobain found for four days, despite Grant and Dylan Carlson - the dead man’s best friend who provided the weapon - searching his house twice?) In the end though he - and we - realise scraps do not a murder make, even when Love’s own father (a deeply troubling man) seems intent on lynching his own daughter.

Events come to a head at the annual ACLU awards where Love is guest of honour. Facing her down, Broomfield is suddenly struck dumb, only to be hustled, courage restored, off stage when he spontaneously mounts the podium after her speech. And there is certainly something unpalatable about her image make-over, especially in light of Broomfield’s answerphone tapes of a less-guarded Ms Love threatening journalists.

Mired in legal twists, the film makes for funny, queasy, compelling viewing - a film about the same fate, control and paranoia that did for Cobain in the first place.