WASHINGTON — Senator Vitter of Louisiana may be called to testify on behalf of a woman accused of running an upscale Washington prostitution service, attorneys said yesterday at the opening of trial.

The Republican senator was among several possible witnesses identified yesterday in the racketeering and money laundering case against Deborah Palfrey. Among others on the list is Harlan Ullman, the military strategist who created the concept of “shock and awe” that America used to open hostilities against Iraq more than five years ago.

Prosecutors said they planned to call about a dozen former escorts and several clients.

Mr. Vitter, a Republican senator in his first term, has acknowledged being involved with Ms. Palfrey’s escort service. But after issuing brief statements apologizing for “a very serious sin,” he has ducked follow-up questions. At trial, he would not have that luxury.

Prosecutor Catherine Connelly called the witness box “maybe the hottest seat in D.C. this year.” Attorneys for both sides told jurors they would see former clients discussing embarrassing and sometimes graphic details about their personal lives.

“It gives me no great pleasure to walk these people through these situations,” Ms. Palfrey’s attorney, Preston Burton, told jurors during opening statements.

Mr. Burton told jurors that Ms. Palfrey ran a high-class fantasy business. Clients called in looking for a date, he said, and Ms. Palfrey got paid whether they played cards, saw a movie, or — in the case of a few women who chose to — had sex. The escorts signed a contract promising not to break the law, he said, and the clientele was made of up “educated people who know when they’re crossing the line.”