Unfinished sympathies: "Margaret"

Margaret is an example of a wilful film: so wilful, in fact, that its heroine isn't even called Margaret. Wilfulness defines Kenneth Lonergan's long-delayed follow-up to 2000's well-received You Can Count on Me, which began filming in 2005, is copyrighted to 2008, and was only released to cinemas at the back end of 2011 after protracted rows between a filmmaker keen to make a three-hour state-of-the-nation opus about America in the wake of 9/11, and a studio (in Fox) rather keener for either multiplex pablum or straightforward awards-bait, and on no account for the result to exceed two hours and thirty minutes. The delays are apparent in Margaret's every dragged foot of celluloid: the cinemas characters go to on dates are screening Flightplan and The 40-Year-Old Virgin, several members of the cast are recruited from Lonergan's big mid-Noughties stage success This is Our Youth, and its star, Anna Paquin, appears notably more voluptuous than she does in her current incarnation on vampire romp True Blood, the hit TV series that has (not inappropriately) come to suck the life out of her.

The version currently on release is a two hour, twenty-nine minute and forty second fuck-you gesture reportedly assembled, with Lonergan's permission, by Martin Scorsese and Thelma Schoonmaker, confirming this as an intrinsically New York story, but also how one aggrieved side in this dispute was as hung up on contractual obligation as the other. The result is fascinating, but lamentably unfinished: Margaret might well have been a masterpiece at two hours or three, but the compromise makes for a variable experience, and you come away admiring it for its vivid flare-ups, rather than its overall shape, of which this cut, at least, has very little.

The narrative proceeds from an accident: not a contrived, message-inducing accident, as in Crash and its imitators, but a real and upsetting accident, one that has dire consequences for all concerned. Paquin's Lucy Cohen is a bright if self-involved teenager of separated parents; she may have inherited some of her characteristics from her highly-strung actress mother. One day, while out shopping for the perfect cowboy hat, she finds it adorning the head of a bus driver (Mark Ruffalo), and Lucy's attempts to wave the vehicle down for her own purposes result in the death of an innocent, and in some ways her own innocence: in the aftermath of the incident, she struggles to deal with the weight of responsibility heaped upon her, lacking the maturity to fully comprehend what she's got herself into, instead charging through meetings with cops and lawyers like a headstrong sixth-former stuck on the one ethics class project she cannot see through.

Lonergan, for his part, has his sights on the heightened sensitivity that characterised America in the days, months and years following September 2001. He has an undeniable gift for writing confrontations between individuals credibly harassed by screaming children, life-or-death situations, or simply a brother tinkling atonally at the piano. Lucy's blazing rows with her teachers (Matt Damon, Matthew Broderick, neither quite pinned down in this cut) and her melting-pot of classmates feel less spontaneous than subsequent sequences in Laurent Cantet's The Class, but they're far less schematic than those in Crash, and Paquin plays every note of this bratty, infuriatingly wilful character more or less to perfection: it's one of the great screen renderings of adolescence, and it's something of a shame it should have ended up at the heart of such a compromised work.

Margaret is legitimately knotty in its consideration of the legal ramifications of Lisa's case, but I got the sense Lonergan had written and directed himself into a cul-de-sac out of which he couldn't edit himself satisfactorily. This version of his film is ragged - which sort of suits its content - and plays in 2011 like a revival of a history play that's landed at a moment when America has more pressing problems than cowboy hats and racial schisms. Whole elements and subplots either needed finessing or omitting altogether: Jean Reno, for a start, testing out the "comedy foreigner" schtick that would soon grace sub-par kiddie pics (The Pink Panther), in a run of vaguely superfluous scenes as suitor to Lisa's mother Joan (J. Smith-Cameron). Vaguely superfluous, that is, until you learn that Smith-Cameron is the director's wife - could it be that Lonergan was simply too close to too much of this material? Certainly, the film appears in thrall to/entirely indulgent of* (*delete as appropriate) the theatrical world Joan inhabits, and it may be telling that the film's most fervent critical admirers share a love of Charlie Kaufman's folie de grandeur Synecdoche, New York, an entirely dissimilar film, save that it appears to dramatise something of Margaret's own troubled genesis.

I'm rather of the camp that finds this cut's shapelessness a problem, particularly after its taut and potent first half, though I should, in all fairness, offer the caveat - a caveat one feels Team Margaret's enthusiastic cheerleaders are clinging to - that something is shapeless is almost certainly more truthful to the unsettled America of the mid-Noughties than, say, the self-contained, sixty-minute pieties of an Aaron Sorkin West Wing special. Margaret, its title deriving from a Gerard Manley Hopkins poem, is wilful in that it has will, ambition, moral purpose; it may be worth seeking out for its flickers of greatness, and occasionally something more besides. If nothing else, it's a miracle that a film that has been hacked around all over the shop, has this much baggage, and this much on its plate, should still find room for three wise words on the subject of giving blowjobs: "Just... be careful". For once in this protracted production, moderation - for the pun, let's say a wiser head - prevails.

Margaret is currently showing at the Odeon Panton Street in London, before opening wider from Friday.