Security correspondent, BBC News
The tribunals used for putting suspects on trial at Guantanamo Bay are a "stain on America's military", a former military prosecutor has told the BBC in his first interview since resigning.
For Lt Col Darrel Vandeveld, a devout Catholic, the twin responsibilities of religious faith and military duty led to a profound moral crisis.
His resignation has led to charges against six inmates being dropped, at least for now, and called into question the possibility of a fair legal process at Guantanamo.
"I know so many fighting men and women who are stained by the taint of Guantanamo, so I'm here to tell the truth about Guantanamo and how a few people have sullied the American military and the constitution," he told me during an interview in his home town of Erie, Pennsylvania.
A reservist, Darrel Vandeveld was called up as a military lawyer after 9/11 and served in Iraq, Bosnia and Africa.
In 2007, he became a prosecutor for the military commissions which tried terrorist suspects held at Guantanamo Bay, a role he took enthusiastically.
"I went down there on a mission and my mission was to convict as many of these detainees as possible and put them in prison for as long as I possibly could," he told the BBC.
"I had zero doubts. I was a true believer."
But his zeal did not last long.
When he arrived, he says he found the prosecutor's office in chaos, with boxes scattered around the floor, files disorganised, evidence scattered in different places and no clear chain of command.
And more seriously, he soon discovered that defence lawyers were not receiving information which could help clear their clients, including evidence that suspects had been "mistreated" in order to secure confessions.
Accused of attack
It was one case in particular, that of a young Afghan called Mohammed Jawad, which caused most concern.
Mr Jawad was accused of throwing a grenade at a US military vehicle.
Col Vandeveld says that in a locker he found indisputable evidence that Mr Jawad had been mistreated.
After Mr Jawad had tried to commit suicide by banging his head against a wall at Guantanamo, Col Vandeveld says that psychologists who assisted interrogators advised taking advantage of Mr Jawad's vulnerability by subjecting him to specialist interrogation techniques known as "fear up".
He was also placed, Col Vandeveld says, into what was known as the "frequent flyer" programme in which he was moved from cell to cell every few hours, with the aim of preventing him sleeping properly, and securing a confession.
A devout Catholic, Col Vandeveld found himself deeply troubled by what he discovered.
But the classified nature of his work meant he was unable to share his growing doubts with friends and family.
As a result, he took the unusual step of emailing a Jesuit priest called Father John Dear, who is a well known peace activist.
In his email, Col Vandeveld talked of having "grave misgivings".
Father Dear was initially unsure if the email was serious and fashioned a quick reply.
"I sort of didn't believe it. But on the off chance he was a military prosecutor I wrote back and said 'quit'."
Col Vandeveld says his jaw dropped when he read the email, adding: "I lived in dread of that answer."
But eventually he did resign and has chosen to speak out about what he saw, giving the BBC his first interview.
"I never suffered such anguish in my life about anything," he says, looking back over the period.
"It took me too long to recognise that we had abandoned our American values and defiled our constitution."
Col Vandeveld was prosecuting six cases, including that of Binyam Mohamed, the last British resident held at Guantanamo.
After his resignation, charges in these cases were dropped but with the possibility they may be re-filed at any point.
Col Vandeveld declined to discuss details of Mr Mohamed's case and others which remain classified.
But Binyam Mohamed's lawyers say he was tortured as part of the CIA's extraordinary rendition programme and are hopeful that he may not be charged again, on the grounds that this might reveal too many details of the rendition programme.
Col Vandeveld was forced to undergo a mental status evaluation after expressing his concerns and his military career is over.
But he has returned to his community in Erie where local newspapers have praised the stand he took. He has no regrets.
In response to his claims, a Pentagon spokesman told the BBC: "We dispute Darrel Vandeveld's assertions and maintain the military commission process provides full and fair trials to accused unlawful enemy combatants who are charged with a variety of war crimes."
President-elect Barack Obama has said he wants to shut Guantanamo but no-one thinks it will be easy.
Col Vandeveld believes that it is possible though.
"No justice will be obtained at Guantanamo," he said. "And if that entails moving them (the suspects) temporarily to the US for trial: so be it."