Anesthesia frequently causes sexual hallucinations in patients, a doctor testified Monday in the trial of a Mt. Lebanon oral surgeon accused of sexually assaulting patients while they were drugged.

“(Sexual allegations) have appeared throughout the history of anesthesia,” Dr. John Butterworth testified. “It’s notable how real they appear to the complainant.”

Dr. Robert John Boyda Jr., 44, is accused of sexually assaulting 17 female patients at his offices in Robinson and Scott from 2002 through late 2007, when two patients went to police.

Defense attorney William Difenderfer has argued the allegations are side effects of the anesthesia.

Butterworth, the Robert K. Stoelting professor of anesthesia at Indiana University in Indianapolis, was the first witness Difenderfer called after the prosecution rested yesterday. The trial began April 27.

Many of the victims testified they recalled Boyda assaulting them in the recovery room but then fell back unconscious and could not remember anything that happened after that.

Dr. Edward Dench, an anesthesiologist, testified for the defense that it would be possible to wake up abruptly after being administered drugs and remember events. Once awake, however, patients would not fall unconscious again.

Dench testified the victims’ testimony was consistent with dreams.

“Dreams are very powerful memories,” he said.

Allegheny County Common Pleas Judge Anthony M. Mariani is presiding over the nonjury trial. It is expected to resume today.

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