Former Staff Sergeant Ivan "Chip" Frederick, who has been jailed for abuse of inmates at Iraq's Abu Ghraib prison, is the third US soldier to be convicted in the case.
Frederick said he knew what he was doing was wrong
His eight-year prison term, reduced from 10 years after a plea bargain, is the toughest of the three sentences as yet given - although lawyers say they intend to appeal.
He was also reduced to the rank of private, and given a forfeiture of pay and a dishonourable discharge.
The 38-year-old non-commissioned officer (NCO) had pleaded guilty to charges of conspiracy,
dereliction of duty, maltreatment of detainees, assault and
committing an indecent act. He said he knew what he was doing was wrong.
But he has also criticised the way the prison was run during his time there, saying it was managed in an arbitrary way that encouraged abuse.
Frederick is a reservist military policeman who had served as a civilian prison officer at a jail in Buckingham, Virginia, before leaving for Iraq in February 2003.
He comes from a family with military traditions, his uncle a Vietnam veteran with 20 years' army service.
As a member of the Maryland-based 372nd Military Police Company, he was sent to the prison in October 2003 as the NCO in charge. He oversaw the night shift in a part of the prison known as the "hard site" until December of that year.
He said that he found a facility in total chaos, where morale was low and prisoner abuse was already rife.
Among other things, Frederick admitted to forcing prisoners to masturbate and punching one man so hard he needed resuscitation.
He also said he hooked up wires on the hands of a detainee.
who was told he would be electrocuted if he fell off a box.
He said he was trying to prepare the prisoners for interrogation.
He said he could have stopped the abuse, but did not.
But he has also tried to blame his superior officers, and said that when he questioned the degrading treatment of prisoners, he was told this was how military intelligence wanted it.
The scandal came to light in April this year, when photos and video were published showing US soldiers
abusing naked Iraqis.