Jacques Vergés is an enigma shrouded by mystery inside a conspiracy. An anti-colonialist since his childhood, Vergés was a student friend of Pol Pot, the future dictator of Cambodia. He made his name defending Algerian heroine (and future wife) Djamila Bouhired and earned instant notoriety for agreeing to represent the Nazi Butcher of Lyon, Klaus Barbie. Then, having disappeared for eight years that have still to be satisfactorily accounted for, he returned to take on such insalubrious clients as Carlos the Jackal, whose wife, Magdalena Kopp, became a close personal friend.

But while this confident charmer is the nominal subject of the fascinating and deeply disconcerting documentary Terror's Advocate, maverick film-maker Barbet Schroeder is equally interested in Vergés's fellow travellers, mostly shadowy characters who forge blood-curdling links between Nazism, various Islamic jihadists, the Red Army Faction and the Stasi. Schroeder also refuses to skirt the awkward questions about France's conduct in maintaining its crumbling empire and the roles that Moscow and Washington played in destabilising regimes on every continent during the Cold War. With on-screen footnotes explaining the intricacies of global terror, this is a superbly researched and structured provocation that reveals how dark and dangerous our world really is.

Sadly, the same can't be said for Morgan Spurlock's Where in The World Is Osama Bin Laden?, which proves a major disappointment after the intelligent satire of Super Size Me. Abandoning his pregnant partner to travel through the tinderbox territories of the Muslim world in order to eliminate the supposed brains behind 9/11 before his baby is born, Spurlock packs the action with gauche videogame graphics designed to capture the imagination of attention-deficient juvenile audiences and raise a smile from those postmodern cynics who reckon that George W.Bush embarked upon his Iraqi crusade with a similar sense of kick-ass idiocy.

But this right-on flippancy soon descends into Borat-like superciliousness, as Spurlock reduces everything from Islamic theology and suicide-bomber psychology to cartoonish soundbites whose glibness contrasts dismayingly with the arrogance of the interviews he conducts with ordinary people to gauge their support for Al-Qaeda.

Posing as the Voice of American Reason, he regurgitates every ill-informed cliché, whether lamenting the bombing of an Israeli school, winding up the residents of an ultra-orthodox Jewish conclave or delighting in discovering a universal loathing for Bin Laden throughout his so-called homelands.

Compare this sloppy, naive and unforgivably smug effort with the conspiracy theory tracts on offer at The ICA in London, before they're released on DVD later this summer.

It's 40 years since Sirhan Sirhan was found guilty of shooting Robert Kennedy in the kitchen passage of the Ambassador Hotel in Los Angeles on June 5, 1968. However, in RFK Must Die, journalist Shane O'Sullivan questions whether the Palestine-born gunman acted alone or was even aware of what he was doing when he pulled the trigger.

The notions of Manchurian candidacy are hard to swallow. But O'Sullivan does a solid job in piecing together evidence connecting Sirhan to the mysterious girl in the polka-dot dress who was seen running from the kitchen area. And he also assembles a credible indictment against the CIA, using lingering resentments from the Bay of Pigs fiasco and insider identifications of key personnel at the scene of the crime to back up his speculations. But he also has the decency to admit the flimsiness of his case and his failure to convince in no way detracts from the film's fascination.

d=3,3,1Andrey Nekrasov's Rebellion: The Litvinenko Case is considerably less cogent and, consequently, far more specious. The director makes no bones about his friendship with the former KGB officer who defected to Britain after accusing the Kremlin of ordering the execution of Boris Berezovsky. But a naked polemic would have been infinitely preferable to this cumbrous jumble, which seems to be more about Nekrasov himself than any rational theories about who placed radioactive material into the talkative exile's tea cup and at whose behest.

The pick of the triptych, therefore, is the Winterfilm Collective's Winter Soldier, which was filmed shortly after the infamous 1971 My Lai Massacre at a Detroit forum designed to give veterans the freedom and support to blow the whistle on what they had seen and/or done in Vietnam.

Although many are clearly discomforted by the closeness of the cameras, they testify with a mixture of frankness, shame, regret and dismay that contrasts starkly with the unblinking propagandist optimism peddled by the media throughout the conflict.

Their accounts of war crimes, manipulated casualty figures and the dehumanising effects of doing one's duty as it was hammered into them from boot camp onwards are sickening in the extreme, all the more so for the fact that these men have remembered all too late that they were raping, torturing and slaughtering fellow human beings.