A corrections captain and his fellow officers beat a prisoner because they were “intent on teaching him a lesson” after the inmate refused to obey an order to remove his T-shirt, an assistant U.S. attorney, Sarah Coyne, told jurors yesterday at U.S. District Court in Brooklyn.

Prosecutors are accusing Salvatore LoPresti, the former jail officer, of then trying to cover up the abuse at Metropolitan Detention Center, in the Sunset Park section of Brooklyn, by faking a suicide scene in Robert George’s cell and claiming he was injured as officers tried to stop him from committing suicide.

In opening arguments yesterday morning, Ms. Coyne described the alleged episode as an “abuse of trust.”

Mr. LoPresti “chose to inflict his own form of punishment rather than abide by the rules of the prison,” she said. “This case is about the abuse of power and the abuse of trust.”

Four other former and current officers charged in the case have pleaded guilty in recent weeks, but Mr. LoPresti, who sat quietly yesterday in the courtroom in a dark suit and made notes as the prosecutor spoke, is maintaining that he is innocent.

An attorney for Mr. LoPresti, Zachary Margulis-Ohnuma, said his client is a “compassionate” man who knew George well and was concerned about his mental health.

George had a history of fighting with guards.

Ms. Coyne said she would call guards who were present at the time of the incident to the witness stand. The guards are expected to tell the jury that they obeyed their captain’s orders, she said. Prosecutors also plan to call a jail psychologist, who is expected to testify that George told her he never tried to hang himself.

George will not testify because he has since been deported to his native Ghana after finishing his sentence.

The jail was the subject of a Justice Department report on the alleged abuse of Muslim men detained there shortly after the terrorist attacks on September 11, 2001. The inmates have since filed complaints that list Mr. LoPresti as a defendant.