Updated

Louisiana Sen. David Vitter may be called to testify in the upcoming trial of a woman accused of running a high-end Washington prostitution ring.

The Republican senator was identified Monday as one of several possible witnesses as jury selection began in the racketeering and money laundering case against Deborah Palfrey. Vitter has acknowledged being involved with her escort service. But after issuing brief statements apologizing for "a very serious sin," he has ducked follow-up questions.

On the witness stand, he would not have that luxury. One of Palfrey's previous attorneys has said he wanted to make Vitter say exactly what services Palfrey's company provided the senator.

Palfrey maintains that her firm, Pamela Martin and Associates, offered fantasy services, not sexual ones. Any woman who sold sex was a "rogue escort" who violated company policy, she says.

Vitter's attorney did not return a message seeking comment Monday.

Palfrey's attorney, Preston Burton, also named Randall Tobias, a former senior State Department official, as a possible witness. Tobias resigned his post last year after phone records linked him to the escort service.

Prosecutors listed among their witnesses several former escorts as well as military strategist Harlan Ullman, who is known for developing the "shock and awe" warfare strategy.

Palfrey says Ullman was a regular client. Ullman has declined to discuss what he has called "outrageous allegations."