It took a death threat to persuade Tarita Virtue to take the stand against her former boss and mentor, Anthony Pellicano, the self-styled “private eye to the stars” who goes on trial in Los Angeles this week.

Virtue, once described by an American magazine as “Hollywood’s sexiest private investigator”, is a reluctant witness in a case that will expose the dirtiest secrets of the film business.

In a week when Hollywood is congratulating itself on saving tonight’s Oscars ceremony, it will cast a cold light on how business is conducted in the world’s film capital – and the insecurities of some of its top celebrities.

Pellicano, 63, already jailed for hiding grenades and explosives in his office safe, is facing 110 additional charges, including corrupting police and bugging the telephones of dozens of stars, such as Sylvester Stallone. He also boasted of bugging Nicole Kidman’s phone during her divorce from Tom Cruise.

Last week, in her first newspaper interview, Virtue said that despite Pellicano’s thuggish ways she had remained loyal to him until he telephoned her parents’ home in Florida and threatened her life.

Virtue, who was executive vice-president at Pellicano Investigations, said that she kept quiet after he was arrested in 2002 on the explosives charges, but then he “mysteriously” heard she was being pressured by the FBI to give evidence against him.

“He phoned my parents in Boca Raton and said, ‘It’s a damn shame – you can kiss your daughter goodbye’.”

There is no doubt that it was a death threat. “I worked with Anthony for three years and I took it very seriously. My father put in bulletproof windows at home and the FBI made it clear that I should leave Los Angeles in a hurry,” she said last week.

“I was away undercover for a year. It was a hard time, not telling friends where I was. I’ve returned to Los Angeles because the FBI say I have to give evidence, otherwise they’ll prosecute me as well. I’m the key witness who saw it all.”

Virtue, 38, is lying low in northern Los Angeles. She feels that her life is on hold until she testifies against the private eye known by his enemies as “the Big Sleazy” and sees him jailed for life. “I’ve even hoped he would have a stroke and die in prison, which is not like me at all,” she confessed.

This was not the life that Virtue, a former beauty queen, had expected when in 1996 she took a job at Pellicano Investigations, working directly for the stocky Italian-American, who was so obsessed with mafia rituals that he insisted his children kiss his hand.

“My job was to listen to hundreds of hours of taped telephone calls and work out what was useful to our clients,” she said. For three years Virtue was the only woman allowed inside the “war room”, a locked office at Pellicano’s West Hollywood headquarters, where the FBI says he used a bank of computers to tape illegally hundreds of conversations between celebrities and their lovers, lawyers and advisers.

The FBI says that Pellicano taped Stallone’s phone calls on behalf of a former financial adviser whom Stallone was suing, to persuade him to drop the case. Years earlier Stallone had hired Pellicano in another case and declared: “With Anthony, when you are a friend, you are family. When you are not, you’ve got problems.”

Last week Stallone said he was ready to go to court to testify against his former friend.

The roll call of potential wit-nesses runs to nearly 70 pages,a who’s who of film executives who have employed Pellicano in corporate or personal battles since the 1980s. Kevin Costner hired him to deal with a stalker, and Bert Fields, Tom Cruise’s lawyer, asked him to end a gay blackmail threat.

Pellicano’s agency collapsed in 2002 when a reporter investigating the action hero Steven Seagal discovered a rose, a dead fish and a threatening note on her car’s smashed windscreen.

The FBI raided Pellicano’s office and closed down the war room. Virtue, who had been fired several times by Pellicano, was finally out of a job.

It has taken five years for the FBI to prepare its case against him, but it is confident that it will jail him for life.

Already one of his clients, John McTiernan, the Die Hard director, has been jailed for four months for lying to the FBI about him. Pellicano denies all charges and says he will be a free man again by the summer.

Video: Anthony Pellicano in his younger days on his glamorous work

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