Lindsay Lohan: Fallen star in search of a happy ending

If you really want to understand Lindsay Lohan, you could do worse than start with her fingernails.

This week, the Hollywood actress celebrated her 24th birthday in a Beverly Hills court where she was sentenced to 90 days in prison for violating her probation. She had missed too many of the alcohol education classes she'd been ordered to attend following two driving under the influence (DUI) offences.

In her halting, contrite defence, she blamed her schedule and time working with children in Morocco. "I don't want you to think I don't respect you and your terms because I really did think that I was doing what I was supposed to do and I mean that with all my heart." Judge Marsha Revel was unmoved. As the verdict was read out, Lohan's eyebrows rose, her jaw dropped, her strawberry blonde hair tumbled loose from its demure pleat and, finally, her freckled face scrunched into tears.

We know all this, of course, because every last second was played out to the whirr and click of the cameras. As the post-courtroom analysis began in the world's media – was this just another compelling performance from Lohan? Or was the sentence unduly harsh, making an example of a high-profile defendant? – another story was already unspooling. A canny picture editor had zoomed in on Lohan's middle finger, which she had pressed anxiously to her lips and swivelled towards the judge throughout the hearing. There, inked in black letters on a pastel swirl of varnish, was Lohan's own verdict: "Fuck u".

What does this fingernail rebellion tell us about Lohan? Sadly, almost everything. It sums up, in tiny lower-case detail, a life lived through a telephoto lens. The obscenity is childish – the kind of trick a high-school pupil might pull on her teacher – but also shows awareness that her every move is captured, homed in on, analysed. Whether the message was meant for the judge, her father (of which more later) or the paparazzi themselves is irrelevant; Lohan knew that, after the judge's summing-up, she would have the last word.

Well, not quite. She later took to Twitter to address the manicure furore. "Didn't we do our nails as a joke with our friend dc? it had nothing to do w/court... it's an airbrush design from a stencil xx." It was followed by the Universal Declaration of Human Rights – delivered, naturally, in 140-character morsels. A court case for our times, then, played out not in camera but in the gossip columns and social networking sites that Lohan calls her home as much as the Hollywood Hills.

Whatever Lohan's punishment turns out to be – she is unlikely to serve more than 23 days behind bars – when she arrives at the Century Regional Detention Facility in Lynwood, Los Angeles, on 20 July, it will be the culmination of a particularly rocky six months for an actress intent on redefining the role of Hollywood hell-raiser for the 21st-century. In January, her clothing line, 6126, was accused of copying. (The label said any similarities were "purely coincidental".) In March, she was sacked by Ungaro after just one critically panned collection (the unveiling of which she missed at Paris fashion week). In April, she was dumped from The Other Side, in which she was due to star opposite Woody Harrelson, after the film's financiers decided she was "unbankable". In May, she fell off a yacht in Cannes when she was supposed to be preparing for a hearing in Beverly Hills. Claiming to have had her passport stolen, she made it to court four days late.

In between, there have been nights out – a parade of exposed underwear, stilettos filled with mysterious powder and dishevelled pratfalls down yacht steps and over cactus plants. There have been spats with Hollywood it-girls, family feuds and an exhaustively documented on-off romance with the DJ Samantha Ronson. When the couple, dubbed LiLo and SamRo by gossip hounds, broke up last year, Lohan made a spoof online dating profile for the website Funny or Die. "I'm an actress, model, entrepreneur and I've single-handedly kept 90 per cent of all gossip websites in business," she simpered. "And I never lose my Google hits – only my underwear."

The only thing Lohan hasn't done in the past six months is a film. For all her party girl behaviour, Lohan is not famous simply for being famous, or for being a famous drunk – she is an actress. But she hasn't "opened" a movie since 2005's Herbie: Fully Loaded. Her last film, Labor Pains, went straight to cable. The one before, I Know Who Killed Me, won a record eight Golden Raspberry Awards, including two for Lohan in the Worst Actress category for her dual roles as twins Aubrey (swot) and Dakota (stripper).

As a career low, it came with added bite. Lohan had first come to prominence in 1998 playing twins in The Parent Trap. "Lindsay Lohan has the same kind of sunny charm Hayley Mills projected [in the 1961 original]", wrote Roger Ebert in the Chicago Sun-Times. He wasn't alone in spotting the 12-year old's potential – Disney snapped her up for a three-picture deal.

By then, Lohan was already an old hand. She was born in 1986 in New York, the eldest child of Dina Sullivan, a singer and dancer who may or may not have been one of the Radio City Rockettes, and Michael Lohan, a Wall Street trader. She began her career aged three, the first redheaded child model to be signed to Ford Models, posing for Calvin Klein and Abercrombie & Fitch and making more than 100 commercials.

Her Disney films established her as a perky, freckled and bankable screen presence, but it was her first post-Disney outing, in Tina Fey's Mean Girls, which brought the box-office big bucks and awards. A flirtation with Britney-style pop followed before her graduation to adult films. Performances in independent movies such as Robert Altman's A Prairie Home Companion, Bobby and Georgia Rule, opposite Felicity Huffman and Jane Fonda, brought more acclaim.

But things were starting to unravel. What started as a joke on Saturday Night Live – Lohan sent herself up, warning an inebriated Easter Bunny, "the partying is overshadowing your talent" – quickly became serious. During the filming of Georgia Rule, Lohan was hospitalised, prompting a letter from a studio executive, James G Robinson, which berated her "discourteous, irresponsible and unprofessional behaviour". It continued: "We are well aware that your ongoing all-night heavy partying is the real reason for your so-called 'exhaustion'." A cycle of rehab, lost film roles, car crashes and cocaine possession came next. In 2007 she served 87 minutes in prison for DUI.

Her parents separated when she was three, then reunited, only to divorce three years ago. Her relationship with her father, who was previously jailed for assault, disorderly conduct, and insider trading, and who released recordings of their phone calls, has since deteriorated. Yesterday she replied to his message of support outside court on Twittter: "I love my mother... she is amazing and strong she's all I could ask for and more, by taking on the role of my mother and father all my life."

Lohan still has considerable talent to fall back on – and she knows it. In court, she declared: "I'm not taking this as a joke, it's my life and it's my career... I'd rather be working in the long-run after all, than dealing with this kind of thing for the rest of my life." Though her next film, a biopic of the 1970s porn star Linda Lovelace, sounds like another mis-step, she is also due to appear in Machete, from Quentin Tarantino and Robert Rodriguez. A fairy-tale Hollywood ending could still be hers.

In the meantime, her trajectory has a worrying precedent – one of which she is only too aware. In 2008, she re-created Marilyn Monroe's last photo shoot for New York magazine, building on an obsession which began as a child and which has seen Lohan name her fashion line after the actress's birth date, commission artworks of her and buy Monroe's old flat. One can only hope that her emulation stops before it's too late.

A life in brief

Born: 2 July 1986, New York.

Family: Eldest child of Michael and Dina Lohan. Her mother was a professional dancer and claims to have been part of the Radio City Rockette dance troupe. Her father was a Wall Street trader who was jailed for four years for insider trading in 1990.

Career: Began her career at age three as a Ford model. Her first major role came in 1996 in the TV soap Another World; starred in her first film, The Parent Trap, two years later. She released a platinum-selling album in 2004 and has since started her own clothing and cosmetic lines.

She says: "I'll probably pursue doing more movies, but not horror or movies with killers in them. I'll try to stick to happy movies. I want to act and direct like Jodie Foster. I admire her because she went to college and she's still doing the same thing."

They say: "Lindsay is identifiable. She's not an unreal personality. Audiences can relate to her. She's the reigning teen queen" – Rob Friedman, vice president of Paramount Pictures, prior to revelations about her alcoholism.