One year on, he's the joker in the pack for Oscars glory

Hollywood is expected to mark the first anniversary of Heath Ledger's death by nominating him for the best supporting actor when the Oscar nominations are unveiled today.

The actor, who died from an overdose of prescription drugs at his home in New York, is a clear favourite for his performance as The Joker in last summer's Batman film The Dark Knight.

No actor has won a posthumous Academy Award since Peter Finch more than 30 years ago but after Ledger won a Golden Globe earlier this month, the odds on him breaking that drought have tightened to as short as 10-1 on. The runners and riders in all 24 categories will be announced shortly after 1.30pm, heralding the start of a season that is expected to be defined by a series of David versus Goliath battles between major studio blockbusters and small rivals.

Although independent films have dominated the Oscars in recent years, 2009's competition will see several bigger rivals vying for contention, including The Dark Knight, Wall-E, and The Curious Case of Benjamin Button.

Danny Boyle's Slumdog Millionaire, which was made for just $15m (£10m), topped a remarkable run of form when it won all four of the awards it was shortlisted for at the Golden Globes, and is likely to dominate the billing for the best film award.

Kate Winslet, who won the best actress and best supporting actress titles at the Globes is also hoping to break her duck of Oscar wins. She is expected to be nominated for her roles in The Reader and Revolutionary Road.

The best actor race is shaping up to be keenly contested, with several veteran stars vying for the prize. They include Mickey Rourke, for his comeback role in The Wrestler, Clint Eastwood in Gran Torino, said to be his last major role, and Sean Penn for his portrayal of Harvey Milk, America's first openly gay elected politician, in the film Milk.

Although no superhero movie has ever won the best film award, The Dark Knight is highly fancied by some pundits, who expect its technical excellence to play well with the 4,000 film industry employees who are members of the Academy.

The film's standing as the highest-grossing film of 2008 could also help its chances. Viewing figures for the ceremony have been in steep decline in recent years, a trend some commentators attribute to the judges' failure to reward popular hits.

Meanwhile, Ledger's standing received a boost this week, when it emerged that a woman settled her legal action against a paparazzi agency that secretly videoed her and the late actor in a Los Angeles hotel room strewn with cocaine. The woman, a freelance journalist known only as "Jane Doe", had sued Splash News, a prominent picture agency, over footage its reporters secretly recorded at the Chateau Marmont hotel after the 2006 Screen Actors Guild awards.

It showed a twitching and seemingly-exhausted Ledger sat at a table containing several lines of cocaine. He discussed intimate details of his sex life, long-term drug abuse ["I used to smoke five joints a day for 20 years"] and relationship with the actress Michelle Williams. "I'm in serious [trouble] with my girlfriend," he admitted at one point. "We just had a baby two months ago, and I'm not supposed to be here."

The footage was sold to the TV show Entertainment Tonight after Ledger's death but it was never widely broadcast, because producers of the show swiftly found themselves facing a public outcry. If Ms Doe's complaint against Splash – whom she accused of invasion of privacy, fraud, and intentional infliction of emotional distress – had reached court, that may have changed things.