In a file photo Former Oklahoma district judge Donald Thompson walks into the courthouse in Bristow, Okla., with his wife, Paula, after the lunch recess in his trial Thursday, June 22, 2006. He is charged with four felony counts of indecent exposure which allegedly occurred in his court during trials. [AP Photo]

Serving on the jury in an indecent-exposure trial unfolding in the conservative Oklahoma town in the United States has been a giggle-inducing experience.

Former Judge Donald D. Thompson, a veteran of 23 years on the bench, is on trial on charges he used a penis pump on himself in the courtroom while sitting in judgment of others.

Over the past few days, the jurors have watched a defense attorney and a prosecutor pantomime masturbation. A doctor has lectured on the lengths the defendant was willing to go to enhance his sexual performance.

The white-handled sexual device sits before the jury box for hours at a time. Occasionally an attorney picks it up and squeezes the handle, demonstrating the "sh-sh" sound of air rushing through the contraption's plastic tubing.

The jurors sometimes exchange awkward looks and break into nervous laughter when the testimony takes a lurid turn.

Thompson, 59, is charged with four counts of indecent exposure, each punishable by up to 10 years in prison. If convicted, he would also have to register as a sex offender, and his US$7,489.91-a-month pension would be in jeopardy.

Thompson's former court reporter, Lisa Foster, wiped away tears as she described tracing an unfamiliar "sh-sh" in the courtroom to her boss. She testified that between 2001 and 2003 she saw Thompson expose himself at least 15 times.

"I was really shocked and I was kind of scared because it was so bizarre," said Foster.

She testified that during a trial in 2002, she heard the pump during the emotional testimony of a murdered toddler's grandfather.

The grandfather "was getting real teary-eyed, and the judge was up there pumping on that pump," she said. "It was sickening."

The allegations came to light after a police officer who was in Thompson's court heard pumping sounds and took photos of the device during a break in the proceedings.

Thompson took the stand in his own defense, saying the device was a gag gift from a longtime friend with whom he had joked about erectile dysfunction. He said he kept the pump under the bench or in his office but didn't use it.

"In 20-20 hindsight, I should have thrown it away," he said.

The R-rated testimony has produced occasional outbursts of laughter and surreal scenes. A man who once served as a juror in Thompson's court testified that he never saw the device, but figured out what it was based on movies he had seen.

The comment sent sidelong glances through the courtroom.

"It sounded like a penis pump to me," Daniel Greenwood testified. He said he had seen such devices in "Austin Powers" and "Dead Man on Campus."

Dr. S. Edward Dakil, a urologist called as an expert witness, repeatedly prompted laughter from the jury when discussion turned to the penis pump. Dakil defended use of the device after defense attorney Clark Brewster said it was an out-of-date treatment for erectile dysfunction.

"I still use those," Dakil testified.

Brewster paused.

"Not you, personally?" he asked.

"No," Dakil responded as jurors laughed. "I recommend those as a urologist."