For some of the most powerful men and women in Hollywood it may be hard to concentrate on this year's Oscar awards ceremony.

That's because another big event is about to take place near by — one that will also feature celebrities, media coverage and speeches, but where the outcome will be considerably more dramatic than a golden statue for Best Picture.

It is the long-awaited trial of Anthony Pellicano: the infamous celebrity sleuth and professional muckraker whose A-list clients have included Tom Cruise, John Travolta and Michael Jackson, as well as several prominent Hollywood executives and defence lawyers.

Mr Pellicano, 63, a private investigator, has been ordered to attend Los Angeles Superior Court on March 5, only days after the red carpet has been rolled up outside the Kodak Theatre in Hollywood. He and four co-defendants are facing charges of illegal wiretapping and obtaining confidential records, among dozens of other allegations. The charges could be enough to put Mr Pellicano in prison for life. He has pleaded not guilty, as have his co-defendants.

But it is the prosecutor's list of potential witnesses that has worried Hollywood - along with the threat that the trial could expose some of Tinseltown's dirtiest secrets. One version of the witness list, which included 244 names, was leaked to the American media this week.

The celebrities who could be called to give evidence are thought to include the comedian and former Oscars host Chris Rock and the Rambo actor Sylvester Stallone. Also on the list are the television actors Kevin Nealon, from Weeds, and Garry Shandling, former star of The Larry Sanders Show.

Even more remarkable are the names of the Hollywood executives who could appear in court. These are thought to include Brad Grey, the head of Paramount Pictures; Ron Meyer, the head of Universal Pictures; two agents and partners at the Creative Artists Agency and their former boss, the infamous former Hollywood “super-agent” Mike Ovitz. One of Hollywood's more feared lawyers, Bert Fields, is also likely to be compelled to give evidence. Fields's clients have included the Beatles, Warren Beatty, James Cameron, Tom Cruise and Dustin Hoffman.

Other big names who could be summoned include Steve Bing, the wealthy movie producer, Peter Morton, the restaurateur, and the British reality show tycoon and creator of Survivor, Mark Burnett.

According to prosecutors, Mr Pellicano specialised in searching for the dirty secrets of his targets so that his clients could use blackmail to gain a tactical advantage in forthcoming or continuing court cases.

He is accused of using a corrupt system of payoffs to Los Angeles police officers to attain police records, and of inventing his own telephone wiretapping software, known as Telesleuth.

In one case, prosecutors say that Mr Pellicano tried to discredit five women who had accused the software millionaire John Gordon Jones of rape. Mr Jones was acquitted later, but a judge awarded one of the women $6million (££million) in damages, which she never collected because the money was moved offshore.

For some potential witnesses, the trial of Mr Pellicano will bring an opportunity for revenge. Mr Stallone said this week that he was eager to provide testimony against Mr Pellicano, who allegedly once wiretapped his phone. “Why not?” the actor said. “I don't want to be left out.”

It is claimed that Mr Stallone's calls were intercepted in February 2002, the same month that he took action against his former business manager over investment advice involving the Planet Hollywood restaurants. The action was settled eventually.

“In this town, nothing seems as it is,” Mr Stallone said. “There is so much skullduggery.”

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