It is a verdict likely to cause great consternation to lonely prisoners throughout the US penal system. A prisoner in Florida has been found guilty of indecent exposure for masturbating alone in his cell.

Terry Lee Alexander, 20, of Lauderdale Lakes, Florida, was sentenced to a further 60 days in jail on top of the 10-year term he is currently serving for armed robbery, the Miami Herald reported yesterday.

He was prosecuted after a female sheriff's office deputy witnessed him performing the sex act in his cell in Broward County, Florida, last November.

The case drew sniggers from the courtroom as prospective jurors were questioned about their own masturbatory habits and the only witness was asked whether she had considered calling in a Swat team to tackle the defendant.

In reaching their verdict on Tuesday, jurors decided that an inmate's cell was "a limited access public place" where exposing oneself wasagainst the law.

The only witness in the case, Broward sheriff's office deputy Coryus Veal, testified that Alexander did not try to conceal what he was doing as most prisoners did.

She witnessed the act while working in a glass-enclosed master control room, 30 metres (100ft) from Alexander's cell. There was no videotape evidence of the offence.

The prisoner's lawyer, Kathleen McHugh, failed to get him cleared on the grounds that a cell was a private place and what Alexander was doing was perfectly normal.

"Did other inmates start masturbating because of Mr Alexander?" Ms McHugh asked Ms Veal. "Did you call a Swat team?"

"I wish I had," the deputy replied.

Ms Veal, who has charged seven other inmates with the same offence, said she was not against masturbation, but she objected to Alexander performing it so blatantly. She told the court that most inmates masturbated in bed, under the blankets.

The deputy said it was the third time she had caught Alexander masturbating, and she had had enough.

After the verdict, the juror David Sherman said the case was "pretty straightforward".

"The prosecution's case was clear, and the defence did not dispute any of the major elements," he told the Miami Herald.

Mr Sherman said jurors determined that a prison cell, which was owned and operated by the government, was neither public nor private but was a "limited access public place'.'

Ms McHugh asked the 17 prospective jurors who among them had never masturbated. No hands went up.

Prosecutors filed charges in all seven of Ms Veal's other cases, according to a spokesman for the Broward state attorney's office.

The charges were dropped in one of these cases to allow the defendant to begin his sentence in the state prison system on a more serious, unrelated charge. Four of the others pleaded guilty and were sentenced to time served. Charges against the other two inmates are pending.