Pvt. Ivan L. Frederick II, called as a prosecution witness, said he never saw the 27-year-old Harman participate in that or several other instances of mistreatment she is accused of at the Baghdad-area prison. A former soldier, however, testified that he saw Harman humiliate prisoners by helping to handcuff them together in an embrace.
Harman is the second soldier to go on trial in the scandal. Frederick, one of four Abu Ghraib guards to plead guilty, is serving an eight-year prison sentence.
Frederick said he was the person who took a widely seen photograph of Harman and Pvt. Charles A. Graner Jr. with a pyramid of naked prisoners. He said he did not see Harman around when guards forced a group of prisoners to masturbate and simulate other sexual acts - a scene she is accused of photographing.
Harman could get up to 6 1/2 years in prison if convicted.
Another witness, Armin Cruz, who has finished serving his sentence for Abu Ghraib abuses and is now out of the Army, testified that he saw Harman join Graner and Frederick in an episode of mistreatment in late October 2003.
Cruz said three prisoners suspected of raping a teenage boy prisoner were stripped and forced to roll around on a cold concrete floor. Cruz said Harman motioned to the men to roll and to crawl low to the floor, and she helped handcuff them together in an embrace.
Cruz, then a soldier in a military intelligence unit working at Abu Ghraib, said Harman told him guards were allowed to do what they needed to keep "order and justice" inside the prison.
Defense attorney Frank Spinner said in opening statements Thursday that the photos of the hooded prisoner, known as "Gilligan," illustrated "a joking type of thing." But prosecutor Capt. Chuck Neill said in his opening that Gilligan "was trembling, shaking, afraid he was going to be electrocuted."
Frederick testified that the prisoner did not appear to suffer any long-lasting effects from the box incident.
Frederick said a criminal investigator had told him Gilligan was to be deprived of sleep to soften him up for questioning. The investigator said the prisoner might have had information about the whereabouts of four missing U.S. soldiers, the witness said.
Gilligan was released from U.S. custody; the prosecution has said the government tried but failed to locate him.
Frederick said Abu Ghraib was a chaotic, dangerous place operating under a murky chain of command.
"Nobody knew what was going on," Frederick said. "I took orders from three different places."
He and Harman were members of the Maryland-based 372nd Military Police Company.
Harman, a reservist from Lorton, Va., who once managed a pizza shop, is depicted in several of the prison's most notorious abuse photos.