Torin Nelson, who served as a military intelligence officer at Guantánamo Bay before moving to Abu Ghraib as a private contractor last year, blamed the abuses on a failure of command in US military intelligence and an over-reliance on private firms. He alleged that those companies were so anxious to meet the demand for their services that they sent "cooks and truck drivers" to work as interrogators.
"Military intelligence operations need to drastically change in order for something like this not to happen again," Mr Nelson said. He spoke to the Guardian in a series of interviews by phone and email.
He claimed that "many of the detainees at the prison are actually innocent of any acts against the coalition and are being held until the bureaucracy there can go through their cases and verify their need to be released."
"One case in point is a detainee whom I recommended for release and months later was still sitting in the same tent with no change in his status."
Mr Nelson said that the same systemic problems were also responsible for large numbers of Afghans being mistakenly swept into Guantánamo Bay. He estimated that "30-40%" of the inmates at the controversial prison camp had no connection to terrorism.
"There are people who should never have been sent over there. I was involved in the process of reviewing people for possible release and I can say definitely that they should have been released and released a lot sooner," he said.
The former commander of the Guantánamo Bay Camp, Major General Geoffrey Miller, was transferred to Iraq a month ago to overhaul the prison system there, although he has been criticised for his recommendations last year that US prison guards in Iraq help "set the conditions" for interrogations by softening up detainees.
Such allegations have been made before by victims' families and human rights groups but Mr Nelson's story represents the first insider's account by an American interrogator. It amounts to an indictment of a system gone awry, and contradicts claims by the White House and the Pentagon that Abu Ghraib does not represent a systemic problem.
Mr Nelson denies any involvement in the physical and sexual abuse of Iraqis at Abu Ghraib, and is listed in the official military report into the scandal as a witness rather than a suspect. He says he resigned from his job in February in fear for his life, because Abu Ghraib was coming under increasing attack by Iraqi insurgents, and because of his disillusion in the military leadership there. He is now working for a private contractor - but not as an interrogator - in another country that is part of the US "global war on terrorism". He did not want his whereabouts published.
Mr Nelson said he had come forward to speak now because he believed that military intelligence was seeking to blame the Abu Ghraib scandal on a handful of soldiers to divert attention away from ingrained problems in the military detention and interrogation system.
As a witness in an ongoing investigation, Mr Nelson said he could not talk about the abuses of specific prisoners at Abu Ghraib, but he said the nature of the detention system makes the imprisonment and abuse of innocent people all but inevitable.
"A unit goes out on a raid and they have a target and the target is not available; they just grab anybody because that was their job," Mr Nelson said, referring to counter-insurgency operations in Iraq. "The troops are under a lot of stress and they don't know one guy from the next. They're not cultural experts. All they want is to count down the days and hopefully go home. They take it out on the nearest person they can't understand."
"I've read reports from capturing units where the capturing unit wrote, "the target was not at home. The neighbour came out to see what was going on and we grabbed him," he said.
According to Mr Nelson's account, the victims' very innocence made them more likely to be abused, because interrogators refused to believe they could have been picked up on such arbitrary grounds.
"Now, whether the detainees are put into the general intelligence holding area, where they rot for a few months until final release, or if they are placed in solitary confinement because their story seems unbelievable is completely in the hands of the interrogator's opinion," he said. "It is in solitary that the abuses can be committed. So, in theory it is in fact very possible that purely innocent Iraqis could be placed in an environment where they could be brutalised, abused, "softened up" or even killed."
"At Abu Ghraib there were plenty of detainees talking or wanting to talk, but the leadership was focused on the "hard" targets of high-value," Mr Nelson said. "This was mainly because the leadership was almost completely focused on getting the highest ranking Ba'ath party members still in hiding. And many of the interrogators were anxious to "go after" the difficult eggs. They wanted to be the one interrogator who broke the linking detainee and found such and such high value target. They weren't interested in going through the less glamorous work of sifting through the chaff to get to the kernels of truth from the willing detainees, they were interested in "breaking" the tough targets."
Much of the problem lay in the quality of US interrogators, Mr Nelson said, explaining that only the youngest and least experienced intelligence officers actually question detainees.
"Once you get up to a level of NCO [non commissioned officer] or warrant officer you generally get moved into administration. You are taken out of working as an interrogator," he said.
As the number of suspects sucked into the system exploded, the Pentagon came to rely increasingly on interrogators from private contractors to question them. Mr Nelson was one of a team of roughly 30 in Abu Ghraib employed by a Virginia-based firm, CACI International. He believes his decade of experience in military intelligence made him well-qualified to do the job, but he had growing doubts about his colleagues.
"I'd say about of the contractors that it's kind of a hit or miss. They're under so much pressure to fill slots quickly ... They penalise contracting companies if they can't fill slots on time and it looks bad on companies' records," Mr Nelson said. As a result, he added, the quality of CACI's interrogators dropped sharply as demand rose.
CACI International did not respond to a request for comment on Mr Nelson's account. The firm has told other reporters that it has not been contacted by military investigators about the work of its employees at Abu Ghraib. Its recruitment notices seeking interrogators state that the job "requires a top secret clearance" and note that the successful applicant would operate "under minimal supervision."
Mr Nelson worked at Guantánamo Bay as a senior interrogator attached to the Utah National Guard. He said that most of the interrogators there were military professionals, but that by the time he left in early 2003, private contractors had begun to arrive.
There is no evidence of abuses on the scale of Abu Ghraib being committed at Guantánamo Bay, but Mr Nelson said that like the Iraqi jail, it was packed with innocent people, who are only now being released.
"Mistakes were made and people who should never have been sent there ended up there, and it's taken this amount of time to get people to take the decision to get these people out of there," Mr Nelson said.
"All it takes is the signature of a low ranking NCO to send someone right around the world and have them locked up indefinitely but it takes the signature of the secretary of defence to let them go."