Sen. David Vitter will not have to testify about his ties to an upscale Washington escort service, a defense attorney said Monday, sparing the Louisiana Republican an embarrassing trip to the witness stand.

Vitter has been on notice for more than a week that he could have to appear during the prostitution trial of Deborah Palfrey. Palfrey's attorney, Preston Burton, said he would rest his case Monday without calling Vitter or any other witnesses.

Vitter has acknowledged being involved with Palfrey's escort service and has apologized for what he called "a very serious sin." He has since avoided most follow-up questions.

That would have been tough to do on the witness stand. During the weeklong trial, men have testified about how they found the service, how often they called, what they were hoping for and whether they got it during their 90-minute, $250 visits.

Prosecutors kept Vitter off their witness list but he was named on Palfrey's defense list. It is unclear exactly what Vitter would have said to help the defense. Her previous attorney had said he wanted to question the first-term senator about what services he paid for and whether any of his visits included illegal activity.

Palfrey maintains that her firm offered fantasy services, not sexual ones. During the weeklong trial, most of the former escorts testified that they had sex with most of their clients. Under cross-examination, however, they acknowledged that was a decision they made privately with their clients.

The senator was elected in 2004 after representing Louisiana's 1st Congressional District in the House from 1999 to 2004. Vitter and his wife Wendy have four children.

Prosecutors were expected to rest their case Monday without calling any more witnesses, Burton said.

That means the case would also likely conclude without the testimony of military strategist Harlan Ullman or Randall Tobias, a former senior State Department official. Both men had been named among possible witnesses.

Palfrey is charged with racketeering and money laundering for allegedly running a prostitution service for years.