Is America finally ready to forgive Polanski?

The director's legal team claims the judge and prosecutor acted improperly in the 1978 sex case that has hung over him ever since

The American judicial system is a mighty juggernaut, and rarely given to second thoughts. But it now has a chance to show, if not forgiveness, then at least clemency to one of the world's most celebrated film directors.

The opportunity has arisen with the request last week by Roman Polanski, the Oscar-winning director of such movie classics as Rosemary's Baby, Chinatown and The Pianist, for his 1978 guilty plea to the charge of having unlawful sex with a 13-year-old girl to be struck down on the grounds of misconduct by both judge and prosecutor in the case.

The plea-bargain deal was reached after Polanski initially faced charges of rape, drug use and sodomy that could have brought life in jail. But even the lesser charge of unlawful sex with a minor carried a prison term. To avoid such punishment, the Polish-born director fled America, and now lives in France, of which he is now a citizen, and which has made clear it will never extradite him to the US.

At the time the case was a colossal scandal. Polanski was widely seen in the US as a strange and vaguely sinister figure, despite the vast acclaim for Chinatown – still regarded as his career masterpiece – four years before. For an America far more strait-laced than it is now, he seemed symbolic of an era of licence and collapsing moral standards.

Many of his films had grotesque or nightmarish sexual themes; paranoia and psychological breakdown were frequent elements in them. He was a foreigner to boot, with a disturbed and tragic life.

He was born to Polish Jewish parents, and his mother died at Auschwitz. He might have suffered a similar fate, had he not managed to escape from the Krakow ghetto. In 1969 his wife, the actress Sharon Tate, pregnant with Polanski's child, was murdered by the Charles Manson cult.

Eight years later came the episode that has made him a fugitive from American justice to this day. Polanski wanted to take pictures of 13-year-old Samantha Gailey for an issue of French Vogue, which he had been asked to guest edit. Her parents gave their consent.

According to the charges, at a second session in Los Angeles in March 1977 Polanski plied the girl with champagne and sedatives before having sex with her. In his autobiography, Roman by Polanski, the director claimed she had been set up by her mother in an attempt to blackmail him.

Now attorneys for Polanski, who is 75, argue that David Wells, the prosecutor in the case, improperly coached the judge, Laurence Rittenband, during the case, and that all the charges should be thrown out. The Los Angeles District Attorney's office has thus far refused comment.

Whether the American legal system is ready to let bygones be bygones remains to be seen. But for the Hollywood establishment and – most important of all – his victim, Polanski has already won redemption.

In February 2003 he won the best director Academy Award for The Pianist (although he did not attend the ceremony in Los Angeles, for fear of being arrested).

Then earlier this year, Samantha Gailey, now Samantha Geimer and a 44-year old mother of three, finally made her peace with him.

"I think he's sorry, I think he knows it was wrong," she said in an interview about a new documentary on the case, Roman Polanski: Wanted and Desired.

But, she went on, "I don't think he's a danger to society. I don't think he needs to be locked up for ever, and no one besides me has ever come out and accused him of anything. It was 30 years ago now. It's an unpleasant memory ... but I can live with it."