Redacted, (15)

An inconvenient truth

Of all the movies about the war in Iraq so far, Brian De Palma's latest is the one that takes the most risks in its effort to tell the truth. In fact, its modus operandi is intended to underline the difficulty of deciding what "the truth" might be. Redacted – which is current American military-speak for "edited", in the way that "rendition" means kidnapping and torture – is a patchwork movie that emphasises the multiplicity of media whereby the war filters through to us. Because official reportage from Iraq is now government-censored, we have to look in the interstices of the digital world to get reliable information on what's actually happening there.

De Palma presents a fictionalised account of a true story – the rape and murder of a teenage girl, and the slaughter of her family, by members of a US platoon near Baghdad in 2006. He focuses on a group of soldiers stationed at a checkpoint in Iraq, one of whom warns us at the outset, "Don't expect any Hollywood action flick." The soldier is talking directly to a videocam wielded by his comrade, Angel Salazar (Izzy Diaz) – the Recording Angel, presumably – who hopes that a video diary of this tour of duty will be his passport to film school. But other points of view jostle for our attention here, all of them De Palma's invention. There's a French film crew making a documentary; a Jihadist website that shows a kidnapped soldier being beheaded; blogs from the internet, TV newscasts and occasional bursts of grainy CCTV footage that supposedly capture unguarded moments.

The film's principal subject is the mismatch between the bored, ill-disciplined soldiers and the difficult, volatile country they're supposed to be protecting. Whether listening to their profane, joshing backchat or watching as they stop and search an Iraqi vehicle at the checkpoint, nothing is so clear as their absolute unsuitability to the task of rebuilding Iraq's fragile democracy.

The language barrier between the indigenous people and their occupiers proves fatal when a car hurtles past the barriers and, in panic, the soldiers open fire on it. The suspicion that it was carrying terrorists is misplaced: it was a man driving his pregnant sister to hospital, and now mother and child are dead. De Palma throws in the shocking statistic that 2,000 Iraqis have been killed at checkpoints since the war began, yet only 60 have been confirmed as insurgents. The film persuades that we're gleaning such information as we go, and none of it is remotely encouraging.

Retaliation for the checkpoint slaughter comes when the platoon sergeant is killed by a boobytrap bomb. By now, Angel's video diary has introduced us to certain members of his unit, two of them being racist blowhards who've decided that "the only language sand-niggers understand is force". This is somehow finessed in their minds as the right to break in to a local family's house and rape their 15-year-old daughter. They leave behind her burned corpse and slain family.

Two other soldiers accompanied them on this action, one a decent fellow named Lawyer (Rob Devaney), who tried to dissuade the rabid pair; the other was Angel himself, who partially records the atrocity. De Palma is here revisiting his own Casualties of War (1989), which he based on a true story of American soldiers who abducted a Vietnamese girl, raped and killed her. The outline is similar, but De Palma has decided he can no longer tell it as a straight, uninterrupted narrative with famous actors in the lead roles (back then, it was Michael J Fox squaring up to Sean Penn).

Redacted reflects not only the changed times of wireless communications and mediated information, it also investigates the complicitous role of filmmaking itself. As Angel himself comes to learn, "Just because you're watching doesn't mean you're not a part of it." The film has hold of something horribly pertinent, namely the extent to which art colludes in the lurid details of sexual violence. Time was when De Palma's camera would have nosed in so close you could almost smell the blood; in films like Dressed to Kill he sensed his audience's weird enchantment with brutality, and revelled in it. That's not the case here. The rape is only half-glimpsed, and the slaughter of the girl's family is only heard, not seen.

De Palma, better late than never, seems to have recognised his own responsibility, and dramatises the behaviour of the two racist soldiers during and after the event with a kind of dazed disgust. It is really quite something to have a renowned American director basically admit that the US Army has rapists and murderers in its tanks.

Some have taken the film to task for anti-Americanism, but De Palma is surely only redressing the chauvinist Hollywood mainstream that wants to believe America is still the good guy. And his "anti-American" feeling amounts only to this: if you shove uneducated, ill-prepared, fearful young men into a distant country whose culture and language they have no interest in understanding, disaster is bound to follow.

What slightly undermines his film is the purely technical issue of presentation: the rough, improvisatory feel he aims for is let down by some clumsy acting and staging. The cast needed to play it low-key and naturalistic to persuade us of its docu-style realism. A Robert Altman might have worked some alchemy with his overlapping dialogue and ad-libs, but De Palma allows his mostly unknown performers to indulge in loud, macho theatrics that cut against the tell-it-like-it-is immediacy. It's a non-Hollywood film that hasn't cured itself of Hollywood acting.

De Palma, right at the end, reminds us unequivocally where his own sympathies lie: he seals the film with a sequence of genuine photographs of Iraqis, scorched and bleeding, dead or dying, their eyes blacked-out to protect their identities – itself an echo of redaction. He might also have added in the postscript something about that murdered girl, who was actually 14. Her name was Abeer Qasim Hamza al-Janabi.