Never can there have been a greater shoplifting scandal in California than the one that unfolded this week. I refer, of course, to the case of Leonardo Andrade, who was jailed for 50 years for stealing $153 worth of videotapes from two Kmart stores. Although he had never committed a violent offence, he had two previous convictions for theft, so, under California's "three strikes" law, he was sentenced to half a century in prison in 1995. This week, his case was finally being heard in the Supreme Court, where his lawyers argued that 50 years for shoplifting a few videos is a "cruel and unusual punishment".

Of course, it wasn't Andrade who made the headlines for shoplifting charges. It was the woman who last week celebrated, if that is the right word, her 31st birthday in room 304 of Beverly Hills superior court: Winona Ryder. She has played a range of parts in everything from Girl, Interrupted to Little Women, Beetlejuice to The Age of Innocence, but it was a 90-minute security video showing her flitting around Saks Fifth Avenue in Wilshire Boulevard that the jurors had to consider.

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"The best beloved of all things in my sight is justice," says the sign on the inside of the main Beverly Hills court building, but it has been hard to keep sight of it over the last couple of weeks.

Ryder was arrested in December last year and accused of having stolen 20 items worth $5,560 from the Saks Fifth Avenue store, just a few minutes by rollerblade from the courthouse where she was being tried. Among the items were a $760 Marc Jacobs thermal top, a $540 Natori handbag, a $220 Eric Javits hat, a $750 Yves St Laurent blouse and a pair of Donna Karan cashmere socks, worth $80. She has now been convicted of grand theft and vandalism but will not be facing jail time when she appears for sentencing on December 6. After the verdict, the prosecution made it clear that they would only be seeking probation or community service - which in LA often means cleaning litter from the highway while dressed in an orange jump suit.

Just after her arrest, the local district attorney's office announced to the world that a security camera had caught Ryder cutting off the security tags with scissors from four items of clothing. This incriminating evidence was widely reported in the press, but in fact it didn't exist. The security video, as we saw in court last week and as the DA's spokesperson, Sandi Gibbons had to admit, showed no such thing. It was an example of how much the prosecution wanted to win the case that they released this damaging information unchecked.

Ryder's defenders swung into action immediately after the arrest, too, albeit with tongue in cheek. Soon snappy T-shirts with the legend "Free Winona" and "We believe you" were on sale. The shirts' manufacturer, Billy Tsangares, a 41-year-old designer who calls himself a "T-shirt journalist", has been in the courthouse over the past week. He has a store in LA where, he says, actors who have won an Oscar or have a star on Hollywood Boulevard are free to shoplift up to $50 worth of merchandise - up to $25 if they have only have had an Oscar nomination. He has also manufactured a shopping bag with a picture of Ryder on one side and the words "I paid for this stuff" on the other. He hopes Saks will stock them.

But back to the courtroom and what has turned out to be a very odd trial. The first oddity was the decision to allow Peter Guber, a leading Hollywood executive from a studio that had produced two of Ryder's films, to sit on the jury. Guber worked for Sony when the studio made Bram Stoker's Dracula and The Age of Innocence, both of which did good business and in both of which Ryder starred. He was also around when Ryder was hired for Little Women. Between them, the films grossed more than $160m. Could this be perceived as a conflict of interest? Guber thought he had no chance of being selected to serve, but there he was in the jury box on day one. Perhaps the logic was that the jury pool in Beverly Hills is swimming with so many big fish from the film world that you are bound to net some, so why worry?

Beloved justice may also have wondered why Ryder was facing such heavy charges for shoplifting, albeit shoplifting at a high level. The previous district attorney, Gil Garcetti, was often accused of being soft on the rich and famous. His successor, Steve Cooley, who beat him in the election for the post in 2000, had said that Garcetti's credo was "money talks, celebrities walk". Cooley, the suggestion has been, is anxious to show that no one is above the law, however many Oscar nominations they have.

The court was a homely little room, with flowers in vases and pot plants on desks rather than scales of justice and clanging doors. Ryder - dressed "chic but conservative", according to the New York Times style page - sat beside her lawyer rather than in a dock. Outside in the street was the array of satellite television trucks that seemed to have moved en masse to Beverly Hills from Washington after the snipers were caught. Coiffed and freshly powdered television presenters from the local stations reported the developments.

The first witness was a cheery soul called Ken Evans. It was he who suggested that Ryder had told him that she was just rehearsing, on a director's advice, for the part of a shoplifter in a film. Which prompted one commentator, Steve Lopez, to write in the LA Times in mid-trial that "we should count our lucky stars Ryder doesn't play a serial killer in this movie she's preparing for, whatever it might be".

Another Saks security investigator, Colleen Rainey, said that Ryder had given her a different explanation as to why she had the garments. Rainey told the court that Ryder had said "Didn't my assistant pay for it?" when she was apprehended. Then, according to Rainey, Ryder went on to explain that she was preparing for parts in two films, White Jazz and Shopgirl. The former is a James Ellroy novel, the latter a novella by Steve Martin that is to be made next year but without Ryder in the cast.

Ryder's lawyer, Mark Geragos, is a classic Hollywood attorney, the kind who makes witnesses cry and is usually played in films by James Woods or James Cromwell. While our own dear departed George Carman used the scalpel to dismantle witnesses, Geragos prefers a baseball bat. His cross-examination of the security personnel was peppered with "It's a lie, isn't it?" and "You made them up!". At one stage the judge, Elden S Fox, got so fed up that he told him: "Mr Geragos, you are trying my patience." Fox knows all about these cases. As a prosecutor 13 years ago, in the same court, he led a successful case against Zsa Zsa Gabor for slapping a police officer and possessing an open bottle of Jack Daniel's.

Geragos's strategy, familiar to anyone who watches any television series about the American legal profession, was to show discrepancies in the accounts of the Saks security team and to suggest that they wanted to nail a celebrity for the hell of it. To this end, he called a former Saks security employee, Michael Shoar, who told the court that Evans, his ex-workmate, had confided in him over lunch after the arrest that he wanted to "nail that rich Beverly Hills bitch... bring her down - one way or another".

Shoar, it turned out, was in a legal dispute with Saks and had been ordered to stay away from the store. The jury chuckled when this emerged. The trial petered to a conclusion without Ryder giving evidence.

Ryder has always been an unconventional soul. Born Winona Horowitz near Winona, Minnesota, she is the daughter of the archivist to Timothy Leary, the writer and LSD exponent who was also her godfather. Allen Ginsberg was a family friend. When she was a child, her family moved to Petaluma in northern California, where Winona was exposed, at a young age, to the cultural phenomena of the time: at the age of seven she was taken by her father to see the Sex Pistols at the Fillmore in San Francisco. At the age of 10, she was reading Catcher in the Rye, although she said in a recent interview that the JD Salinger character she most identified with was Franny in Franny and Zooey.

She was studying acting by 11 and did her first film at 15. The roles have come rapidly ever since - at such speed, in fact, that she was too exhausted to appear in the part she was due to play in The Godfather Part III. She picked up Oscar nominations for both The Age of Innocence in 1993 and Little Women the following year. This was despite the fact that acting was not her first choice as a profession. She said in an interview with W magazine this summer: "I wanted very much to be a writer or an activist. I wanted to change the world. I never thought of myself as being in any kind of spotlight."

When she was arrested last year and in the spotlight again, much was made of the fact that her career was supposedly going badly. Since then, Mr Deeds, in which she co-starred with Adam Sandler, has taken more than $150m at the box office worldwide, which makes it a successful film by commercial if not critical standards. Rick Lyman in the New York Times suggested that "on a list of possible crimes against humanity, shoplifting must fall somewhere below Mr Deeds and Autumn in New York [another recent unremarkable film]". Simone, in which she appears with Al Pacino and which has been less successful in the US, has also appeared.

But the simple fact is that there are few interesting films with few interesting parts being made in Hollywood at the moment. Ryder's career is no more or less on the up or the down than that of most of her contemporaries. Any ambitious actor would be delighted to have her body of work behind them.

The best actors have good timing, so she can be congratulated on having the jury retire on the day of the mid-term elections, in the midst of talk of war and with the snipers in the Washington suburbs still a focus of public attention. Not that this meant the case passed unnoticed. "Celebrities are always magnetic, celebrities in a jam flat-out irresistible," wrote Howard Rosenberg, the television critic for the LA Times, of Ryder's problems.

The young prosecutor in the case, deputy district attorney Ann Rundle, suggested that Ryder had shoplifted for a thrill. "She came, she saw, she shoplifted," said Rundle in her closing remarks. "We've presented the truth. They've given you a story that could only have been written in Hollywood." Gera gos said that security manager Ken Evans had misrepresented what had happened because he wanted to get "15 minutes of fame". And indeed, fame was at the heart of the case.

In The Frenzy of Renown, perhaps the most comprehensive study of celebrity, Leo Braudy, who teaches at the University of Southern California and says he gets called by journalists for quotes about celebrities on a weekly basis, writes: "For both journalist and audience to be aware of fame is to be behind the scenes and to be behind the scenes is to control rather than be controlled. Whether your particular knowledge is gossip about politicians or movie stars... having such knowledge proves that you're special, that you can't be fooled and that you understand the heart of things." But even after two weeks of trials, miles of footage of television news and acres of newsprint, no one seems really the wiser as to what was behind the scenes of the case in room 304.

More than 50 years ago, in another Hollywood celebrity trial, Robert Mitchum was charged with smoking dope and given 60 days in the slammer. Here is what Time magazine wrote about it in 1949: "The most self-conscious city of a self-conscious nation was in for a first-rate scandal and it hated and feared every whisper of it... Under the klieg-lit, high-pressure, high-paid strains peculiar to Hollywood, some of its supertense citizens sometimes volatilize and take to drink, adultery or dope". Apart from wondering what "volatilizing" is and what the Time reporter had been smoking before he sat down at his typewriter, we have not come very much further in that half century in our understanding of fame and the courthouse.

In career terms, it is hard to know what effect the conviction will have. Probably not much. People may feel that the humiliation of the trial was enough. Robert Downey Jr bounced cheerfully back on Ally McBeal after his times inside for drugs offences. And Robert Mitchum didn't seem too damaged by his "first-rate scandal". Whatever else it is, Hollywood is not a puritanical place and Ryder is not a figure who provokes antagonism. No one died.

Not that Ryder is likely to complain. In that interview with W, the last she gave before her lawyers stepped in, she said: "One major problem I have is that I rarely meet people who don't think they know things about me. Not to complain, because I know movie stars are just not allowed to complain. I've watched them try and it doesn't quite work."

In the best spirit of the entertainment industry, when one show ends, there has to be another waiting in the wings. Sure enough, this week sees the start of the trial for murder of Robert Blake, who is perhaps best known to British filmgoers for his role in the 1968 movie In Cold Blood. Which is essentially what the allegation is against him: that in cold blood he organised the killing of his wife, Bonny Lee Bakley, who was shot dead outside a restaurant in LA in May last year. This is a rather grimmer case than a charge of nicking some socks. Someone did die. And Robert Blake is unlikely to be arguing that he was just rehearsing for a remake of In Cold Blood.

Meanwhile, spare a thought for Leonardo Andrade, whose case has been taken up by the Familes to Amend California's Three Strikes (Facts) and who should have been on the front pages rather than Ryder. On the very day that the prosecution in Beverly Hills was accusing Ryder of being a thrill-seeker, her superiors were at the Supreme Court in Washington defending the state's right to jail Andrade for half a century. It will be weeks before the Supreme Court decide whether 50 years is too tough a punishment for a father who stole some videos for his children to watch, who has already served seven years for this shoplifting episode and who will be 87 before he is due for release.