Coming Soon to a Crowded Courtroom, Steven Seagal

No red carpet is planned. But federal marshals are expected to put up barricades one day this week, as the Brooklyn federal court becomes the locale for one of the hottest acts in town.

Steven Seagal, the martial arts movie star, is expected Tuesday at the Mafia racketeering trial of Peter Gotti and six other men who prosecutors say are members of the Gambino crime family. For weeks, judges, cleaning ladies and just about everyone else at the court have been fretting about getting a seat.

Mr. Seagal, who is 6-foot-4 but looks much bigger in posters, is to testify that he was frightened after being threatened by mobsters and extorted for hundreds of thousands of dollars.

From the start, Mr. Seagal's account of extortion has given a dash of glitter to an otherwise grim trial concerning waterfront corruption and gambling deals. The prosecutors say part of the extortion occurred, Hollywood-style, in a darkly lighted restaurant, Gage & Tollner, in downtown Brooklyn.

The prosecutors say that some of those on trial strong-armed Mr. Seagal, who was in a bitter battle with his longtime producer, Julius R. Nasso. Among those charged with extorting Mr. Seagal is Anthony Ciccone, who the prosecutors say is a Gambino captain, and his reputed mob aide-de-camp, Primo Cassarino.

The prosecutors' story line evokes old tales of organized crime controlling the biggest movie stars. From its start, the case seemed a mixture of reality and show business. A few days after the Gage & Tollner dinner, the prosecutors say they used a hidden microphone to record another conversation (over another restaurant dinner). According to a prosecution transcript, the accused extortionists regaled one another with giggly accounts of how much like the silver screen their move on Mr. Seagal had been.

''I wish we had a gun on us, that would have been funny,'' Mr. Cassarino said, according to a transcript.

Mr. Nasso's brother, Vincent, is said to have answered, ''It was like right out of the movies.'' The Nasso brothers, also charged with extortion, are to be tried separately.

Defense lawyers have seized on Mr. Seagal's colorful, occasionally mysterious past to promise bone-chilling cross-examinations. On Friday, prosecutors filed a motion asking the judge, Frederic Block, ''to protect the witness from harassment and undue embarrassment.''

For example, their motion said, they want to bar any questions about tangled allegations involving an assertion that the German mafia threatened Mr. Seagal, and another confusing claim that involves someone who left a dead fish on the car of a Los Angeles reporter who was investigating Mr. Seagal.

While those might appear to be separate stories entirely, the prosecutors' motion showed that they are worried that their narrative might be hijacked by the defense.

All in all, the jurors may well be confounded by the dazzling mixture of truth and fiction that is likely to surround Mr. Seagal's appearance in the witness box, said Todd Gitlin, a professor of culture, journalism and sociology at Columbia University.

''He has to establish that he's not just playing a part,'' Mr. Gitlin said. ''He has to send cues that he's not just a character.''

Whether or not Mr. Seagal convinces the jurors that he is real, his visit to the trial will be no ordinary day in court, said Benjamin Brafman, a lawyer who has represented Sean Combs, the rap star known as P. Diddy.

Mr. Brafman is not involved in the Gotti trial, but he said courtroom appearances by celebrities were almost always riveting. ''When someone like Steven Seagal walks into a room in a non-Hollywood setting with people who are not accustomed to seeing superstars, it's exciting, it's interesting,'' he said.

Even if the dead fish is never mentioned.