There were no threats issued against Allegheny County Judge Anthony M. Mariani after his controversial acquittal of a South Hills oral surgeon, the judge said.

But in the name of "prudence" he was escorted home Wednesday night by a sheriff's deputy, and his house was under guard overnight.

Judge Mariani Wednesday found Dr. Robert J. Boyda Jr., 44, of Mt. Lebanon, not guilty on all counts after 17 women testified that he had sexually assaulted them while they were under anesthesia.

Judge Mariani, who presided over a nonjury trial, said he believed the women thought they were assaulted. But the fact that they were on a strong cocktail of drugs -- one of which, propofol, has been known to cause sexual hallucinations in rare cases -- made their observations unreliable, the judge ruled.

The extra security precautions came after Judge Mariani revealed last month that he had received a letter claiming to be from 500 former dental and post-graduate students who attended Northwestern University with Dr. Boyda while he was in dental school. The letter claimed that Dr. Boyda had been known for similar behavior years ago.

"If he is found anything other than guilty, our problem will not be with Dr. Boyda Jr., but rather with YOU, and we are prepared to do what would be appropriate in our group consensus opinion at that time," it read. "For now, know that we are all watching and awaiting your decision. If it is as it should be, we will have no further contact, if not, well enough for now."

Judge Mariani said he considered the letter a threat and offered to recuse himself, but Deputy District Attorney Janet Necessary and defense attorney William H. Difenderfer declined.

Judge Mariani yesterday denied reports in other news media that he had been threatened again.

"There was not even an event that occurred that could be misinterpreted as a second threat," he said.

He said that the extra security was a mutual decision between him and the sheriff's department, made in the days before the verdict.

When asked directly if he felt threatened, Judge Mariani responded, "You can't ignore the efforts made," referring to the letter, which was sent to both the courthouse and his law office.

Chief Deputy Sheriff Joseph Rizzo said that on Wednesday, one deputy worked a 4 p.m. to midnight shift, giving the judge a ride home and monitoring his house from outside. Another deputy watched the house from midnight to 8 a.m.

Chief Rizzo said the night was uneventful, and no further special protection for the judge is planned. Judge Mariani returned to court as usual yesterday morning to hear cases.

"It's not uncommon for us to do this," Chief Rizzo said. "If the judge feels uncomfortable, we [provide security]."

The letter, meanwhile, is in the hands of FBI investigators.

FBI spokesman Jeff Killeen said that the bureau has not identified the sender. If the perpetrator is identified, Mr. Killeen said, criminal charges such as extortion or harassment could be filed, depending on the specific language in the letter.

One of the alleged victims in the case said she doubted the validity of the letter and questioned the motives of its author or authors.

"They're cowards for letting us suffer through it and go through what we have, and to send an anonymous letter when they could come forward and help our case," said the woman, who was 42 when, she claims, she was assaulted by Dr. Boyda in 2002.

The Post-Gazette does not print the names of victims or accusers in sexual assault cases.

The woman said she did not sense any maliciousness toward Judge Mariani on the part of the alleged victims, who sobbed and wept in the courtroom after the judge revealed his verdict. Instead, she said, there was a sense of disappointment and loss.

"Every victim and their family members were there to get justice done," she said. "Now we'll just have to trust God's justice. God's vengeance is worse."