Not since the assassination of JFK has home video been this morbidly fascinating. Documentary filmmaker Andrew Jarecki lets the Friedman family do the bulk of the camerawork in Capturing The Friedmans, blending their footage with in-depth interviews to produce a gripping study of dysfunctional family life on Long Island. At its most powerful, Jarecki's movie evokes compassion, fear, anger, pity, revulsion, laughter, and sadness - all at once.

The defining moment in the lives of the Friedmans comes on Thanksgiving Eve, 1987, when police officers force entry into their home and charge Arnold Friedman and his youngest son, Jesse, with multiple sex offences against young boys. Ditsy mom Elaine, her eldest son David, and (the notably silent) middle-son, Seth, are left reeling.

"EXCRUCIATINGLY INTIMATE"

David copes with the ensuing turmoil by recording excruciatingly intimate video diaries, charting the unravelling of family ties and long-simmering resentments that come to boil as the trial date approaches. Cutting excerpts of these with grainy reels of family holidays and birthday parties, Jarecki puts an astoundingly ordinary face to evil.

But the extent of Arnold and Jesse's guilt is thrown into question by conflicting accounts from police detectives, lawyers, professed victims, and the Friedmans themselves. Evidence on both sides swings opinion back and forth, occasionally triggering utter disbelief, as when Mrs Friedman naively considers her husband's motives for possessing child pornography: "He liked to look at pictures of boys and... meditate."

David berates his spacey mother, although he surpasses her for barrel-scraping rationale and generally unhinged behaviour. On the day of the arrests, he parades in front of news crews wearing underpants over his head, shouting, "Look at me! I'm an ***hole!" Laughter may feel inappropriate, but these darkly comic moments illustrate the variance of emotions that makes Capturing The Friedmans such a startlingly vivid and complex portrait. It raises more questions than it answers, but that's the point. Jarecki's film reaches deep inside the well of your darkest fears and drags out a mess of everything that makes us human.