Jonathan Caouette's scaldingly personal film Tarnation looks like one of those underground video loops you might casually stumble into at some über-cool art gallery - and then very uncasually get the hell out of. It's a frazzled collage of assorted video clips, Super 8 home movies, family photographs, surtitles, answerphone tapes and snatches of music, spliced together to form an idiosyncratic memoir - part trip, part video diary - of one young man's life and hard times. There are moments in it when you don't want to watch, and yet you can't look away.
Caouette's story begins with the recent calamity of his mother Renee's lithium overdose, then reels back through the years to uncover a ripe history of mental illness and abuse. Texas-born Renee, a one-time child model, fell off a roof aged 12 and lost the use of her legs. Some months later her parents, Rosemary and Adolph, were persuaded by doctors that their daughter's continuing paralysis might be psychosomatic, and authorised a course of electroshock therapy, twice a week for two years. The effects upon her were, not surprisingly, disastrous: over the next 30 years she would be in and out of institutions, her motor abilities restored but her sanity apparently hanging by a thread. In 1977, during one of her psychotic spells, she was picked up by a stranger on a street in Chicago and raped; her son Jonathan, aged five, was a witness.
At which point you wonder: could it get any worse than this? For Jonathan, unfortunately, it did. His father had scarpered early in life, and for most of his childhood Jonathan was raised by his clueless maternal grandparents. For two years, however, he was relocated to a care home and subjected to violent abuse by his foster parents, an experience that reverberates through this near-Gothic account of growing up.
At first, like so many adolescent boys, Caouette watched horror flicks, and then, armed with a camera, began to make his own. We glimpse his debut Super 8 shocker, rejoicing in the title The Ankle Slasher. At high school, he staged a musical version of Blue Velvet in which the cast lip-synched to Marianne Faithfull songs. In his teens, he was introduced to the avant-garde movie scene by gay friends in Houston and immersed himself in the cult of Warhol and Paul Morrissey.
That strain of underground narcissism must have incubated, because at some point he decided to train the camera on himself and his family: perhaps he realised that the best horror movie was happening right in front of him.
The earliest intimation of this is a deeply disquieting scene in which Caouette, aged 11, plays a solo routine as a battered wife, cringing in fear and fluttering his hands like a pint-size Blanche Dubois. What haunts about the scene is how convincing he is. Later in the film, we are told that the teenage film-maker once smoked a joint spiked with formaldehyde and PCP, which thereafter left him unnaturally dissociated: he seemed able to watch his life from a vantage of complete detachment. Yet the extraordinary impersonation of the abused wife predates this mishap. That was the product of his own psyche, not dodgy drugs.
Another startling aspect of Tarnation is the way it has redefined the term "low budget". Caouette put together his original edit with the iMovie software from his Apple Mac for $218 (about £115), which I imagine would just about cover bagels and an hour's therapy for your averagely self-obsessed New Yorker.
This incredible figure created a buzz about the film when it launched on the festival circuit, and Gus Van Sant, who saw an early cut, lent his name as an executive producer. Since then, it has won prizes and become an inspiration to DIY film-makers.
Without wishing to rain on Caouette's already impressive parade, I wonder if his film is really as marvellous as the reports would have us believe. Vaunted as something in the order of last year's Capturing the Friedmans, another documentary in which a family implodes on camera, Tarnation can match it for sensation but not for balance or incisiveness. Friedmans was kept in tantalising equipoise by its director, Andrew Jarecki, who presented the case of the father and son's alleged child abuse with such evenhandedness that, to the end, the truth remained bafflingly elusive. Caouette, lacking any such distance, seems unrefined, clumsy even, in comparison.
There is a sense that what we are watching, for all its painfulness, has less to do with self-examination than self-advertisement. The experimental technique, with its wipes and dissolves and split screens, keeps drawing attention to itself instead of casting light on his subject.
Something vital is missing here. While one believes that Caouette has sustained a loving relationship with his mother against the odds ("I can't escape her... she's under my skin"), there is reason to doubt that he has been entirely fair to her. At one point he asks her to talk about her troubled marriage (Mr Caouette Sr makes a brief return before wisely disappearing again): Renee plaintively replies that she's willing to talk, only not on film. Later he does film her, while she's still fried, wandering about his kitchen and gabbling hysterically about a pumpkin she's holding.
What exactly has been gained by showing his beloved mum reduced to a pitiful imbecile? Caouette will probably argue that honesty made him keep the camera running, and perhaps it did. But why is honesty so privileged? Isn't tact also part of the autobiographer's art?