With the unholy trinity of sex, crime and celebrity, this documentary is a surefire attention grabber that never lets up. Though Marina Zenovich's film deals with the notorious case of the film director who pleaded guilty to having sex with a 13-year-old, the film's real subject is the California legal system turned upside down by celebrity and media pressure.

Before he was arrested on charges of drugging and raping a minor in 1977, Polanski was already a figure wreathed in shadows. A child whose parents were killed in the Holocaust, he was near the peak of his Hollywood fame when his pregnant wife, actress Sharon Tate, was brutally murdered by members of the Manson family. His traumatic life and his films of violence, insanity and the occult always seemed intertwined. Personally, he had a reputation as a playboy with a fondness for girls, including an affair with then-15-year-old Nastassia Kinski.

The film recounts the details of the crime, using text scrolls of the police statements made by Polanski and 13-year-old Samantha Gailey. At a Vogue magazine shoot at Jack Nicholson's house, Polanski gave the girl champagne and a part of a Quaalude before having sex with her. After Polanski's arrest, the girl's lawyer wanted to avoid putting her on the stand and urged Polanski to avoid trial by accepting a plea bargain. A half-dozen charges against Polanski, including sodomy and furnishing drugs to a minor, were reduced to one charge of “unlawful sexual intercourse” to which he pleaded guilty. The worst he could expect was probation.

By all accounts, the judge in the case, the late Judge Laurence J. Rittenband (he died in 1993) was a media-obsessed, unprincipled fool who bent the rules to make himself look good. The assessment is confirmed by a spectrum of observers, including reporters, Roger Gunson, the assistant district attorney who prosecuted the case, and Polanski's attorney, Douglas Dalton. Even the victim (now Samantha Geimer) said the judge did a disservice to both her and Polanski, whom she publicly forgave in 1997. (For his part, Polanski was less generous: In his 1985 book, Roman by Polanski, he accused Geimer's mother of setting up a blackmail plot against him.)

The film documents how Rittenband dithered, broke promises and ordered the lawyers from each side to play-act arguments in the court before he delivered his prepared judgments. Embarrassed by a photo of Polanski sitting between two women at Oktoberfest in Germany when he was supposed to be working, the judge vowed to put the director behind bars.

Polanski returned to the United States to face sentencing but after consulting with his lawyer about the judge's reliability, and facing a possible 50-year sentence, he decided to flee. The judge's attempt to sentence Polanski in absentia was thwarted when the defence attorney charged that the judge was prejudiced and demanded that he be disqualified.

The secondary story of Wanted and Desired is a portrait of Polanski as a tortured and vilified artist who draws polar reactions from people. Samples from Repulsion, Chinatown and Rosemary's Baby emphasize his thematic interests, which the prosecuting attorney, who caught a Polanski film retrospective just before the trial, summed up succinctly as “corruption meeting innocence over water.”

The film is less persuasive in portraying Polanski as, once again, a victim, this time of American moralism and prudishness. Someone repeats a joke that Gunson, a straight-arrow Mormon, was selected to prosecute the crime because he was the only lawyer in the D.A.'s office who hadn't had sex with an underage girl. Later, we are left with the implication that Judge Rittenband was a hypocrite because he, too, was a playboy with a fondness for young women, though “young” in his case meant women in their 20s, well past the age of consent.

The phrase in the title “wanted and desired” is offered by a producer friend of Polanski's who describes him as “wanted” in the United States, but “desired” in Europe, where sexual behaviour is treated more honestly and artists' dark sides are celebrated. True, Polanski's name evokes sharply divided responses, but the divide isn't that geographical. You'll go to jail for having sex with a minor in France as well. And Polanski's reputation as a film director continues to be exalted in the United States, where he won an Academy Award for best director for The Pianist in 2003.

Polanski did not give an interview for the film, but there are clips from an old television conversation he had with Clive James in a Paris apartment. At the end of the film, Polanski asks rhetorically: “Do you think there's something more to my life than my relations with young women?”

Coming from a sophisticated man, the question sounds surprisingly ingenuous. To paraphrase an old observation, you can build bridges all your life and no one ever yells “Bridge builder!” – but sleep with your mother once.…