WASHINGTON (AFP) - United States Central Intelligence Agency (CIA) lawyers sought guarantees the US spy agency would never be prosecuted for torturing suspects after the Sept 11, 2001 attacks, while other staff warned the programme was an impending "train wreck", documents showed on Tuesday (June 15).
The correspondence provides a new glimpse into tussles within the CIA as it implemented its notorious "enhanced interrogation" techniques aimed at thwarting further attacks.
Fifty documents, released under a freedom of information request from the American Civil Liberties Union, detail the early days of the CIA's use of torture, after then President George W. Bush directed the agency to detain terror suspects around the world.
A July 2002 draft letter from CIA lawyers to the attorney-general sought legal protections before agents interrogated Abu Zubaydah, an alleged Al-Qaeda member who is still detained at Guantanamo Bay.
"The use of more aggressive methods is required to persuade Abu Zubaydah to provide the critical information we need," the letter states.
"I respectfully request that you grant a formal declination of prosecution, in advance, for any employees... who may employ methods in the interrogation of Abu Zubaydah that otherwise might subject those individuals to prosecution."
The Justice Department at the time ruled that certain detainees could be subjected to enhanced interrogation, including the use of the simulated drowning technique known as waterboarding.
The CIA has not used these methods since December 2007, and President Barack Obama banned them when he took office in January 2009.
But the newly released documents describe how some agency employees had misgivings much sooner.
"I will no longer be associated in any way with the interrogation programme," an agency employee stated in a January 2003 memo. The CIA blanked out the name of the sender and the recipient.
"This is a train wreck waiting to happen, and I intend to get the hell off the train before it happens."
The documents show the CIA believed it extracted details from Zubaydah of a purported plot to detonate a "dirty bomb" in the Washington area.
However, a top CIA medical official later said any information could have been obtained through regular interrogation.
"In retrospect, (doctors) thought (he) probably reached the point of cooperation even prior to the... institution of 'enhanced' measures," the official said.
"There was no evidence that the waterboard produced time-perishable information which otherwise would have been unobtainable."
The CIA claims evidence acquired through torture yielded vital intelligence, but a Senate committee later found the brutal methods produced no useful information.
The documents included new details in the case of detainee Gul Rahman, who died half naked - probably from hypothermia - at a secret CIA prison in Afghanistan in 2002.
"Prisoners who possess significant or imminent threat information are stripped to their diapers during interrogation and placed back into their cells wearing only diapers," a death investigation stated.
"This is done solely to humiliate the prisoner for interrogation purposes. When the prisoner soils a diaper, they are changed by the guards."
The ACLU, which represents Rahman's family in a lawsuit, blasted Dr James Mitchell and Dr John "Bruce" Jessen, two psychologists who designed the programme.
"We're seeing just how much Mitchell, Jessen and their CIA co-conspirators knew that what they were doing was wrong and illegal," Mr Dror Ladin, a staff attorney with the ACLU National Security Project, said in a statement.
"They talked about seeking a get-out-of-jail-free card for torturing people, and then discussed how to make sure their victims were silenced forever, even if they survived their torture."
Key to the CIA's detention and interrogation programme was its use of "rendition" - the secret transfer of detainees to countries outside the United States that had a more lenient attitude toward torture.
One man, German citizen Khalid al-Masri, was held captive for five months in a case of mistaken identity.
"His rendition and long detention resulted from a series of breakdowns in tradecraft, process, management and oversight," according to an investigative report.
America's experiment with torture is not necessarily a closed chapter, as presumptive Republican presidential nominee Donald Trump has said he would "bring back a hell of a lot worse than waterboarding".