It is possible that one of the victims of the United States' torture policy is a young, devout Mormon woman from Arizona called Alyssa Peterson. She was a soldier who not only saw the rough interrogation methods that the US military used on Iraqi prisoners, but was deeply troubled by them. Some weeks after formally protesting about them to her superiors, and asking to be reassigned, she took her gun and killed herself. The cause of her death was kept secret for two years, and the mystery of what Peterson witnessed, and the content of the notes she made, still goes on.

It was in September 2003 at Tal-Afar air base, northern Iraq, that Specialist Peterson, serving with a military intelligence section of the 101st Airborne, came across interrogation methods very different from the ones she had known in training. An Arab-speaker, Peterson was assigned to work as an interpreter at interrogation sessions in a unit known as "The Cage". After only two nights, she refused to take further part in the sessions and was reassigned. Then, on 15 September, she shot herself with her service rifle. A notebook recording her thoughts was found by her body. Its contents were blanked out in the subsequent official report.

Her family, in Flagstaff, Arizona, were told she had died from a "non-hostile weapons discharge". It was only after an Arizona reporter, Kevin Elston, investigated, that the army revealed Peterson had killed herself. They refused to say what interrogation she objected to, and maintain that all documents relating to methods used at Tal-Afar have been destroyed.

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But, at Mosul, also in northern Iraq, a former US soldier, Kayla Williams, later told the broadcasterCNN: "There were prisoners that were burned with lit cigarettes. They stripped prisoners naked then removed their blindfolds so that I was the first thing they saw. And then we were supposed to mock them and degrade their manhood."

She, too, objected. Williams had once met Peterson, and conceded the interpreter had personal problems. The official army report into her death, obtained in 2007 by the Arizona Daily Sun, said that she had once been reprimanded for "showing empathy" to detainees. It said her superiors had given her suicide prevention training.

Her body was buried, with military honours, in Flagstaff, Arizona. One of scores of messages on a memorial website reads: "Alyssa Peterson was a shining example to all, a true hero and patriot for displaying empathy and her opposition to torture."