WASHINGTON — Prisoners could be kept awake for more than a week. They could be stripped of their clothes, fed nothing but liquid and thrown against a wall 30 consecutive times.
In one case, the CIA was told it could prey on a top Al Qaeda prisoner's fear of insects by stuffing him into a box with a bug. When all else failed, the CIA could turn to what a Justice Department memo described as "the most traumatic" interrogation technique of all -- waterboarding.
Baring what he called a "dark and painful chapter in our history," President Obama on Thursday released a collection of secret Justice Department documents that provided graphic guidance to the CIA on how far it could go to extract information from terrorism suspects.
The memos provide the most detailed account to date not only of the interrogation tools the CIA employed against Al Qaeda suspects in secret prisons around the world but the legal arguments the Bush administration constructed to justify their use.
At the same time, Obama assured CIA employees and other U.S. operatives that they would be protected from prosecution or other legal exposure for their roles in the nation's counter-terrorism efforts over the last eight years.
"This is a time for reflection, not retribution," Obama said in a message delivered to CIA employees, explaining his decision to release a collection of documents that agency veterans and some senior officials in his administration had fought to keep sealed.
The memos were crafted by the Justice Department's Office of Legal Counsel, a unit that was at the center of a series of debates during the Bush administration over the limits of executive power and counter-terrorism tactics.
One of the authors was then-Assistant Atty. Gen. Jay S. Bybee, who since has been confirmed as a judge on the U.S. 9th Circuit Court of Appeals.
The release of the memos was seen as a test of the Obama administration's commitment to its pledge of transparency, as well as its promise to roll back Bush administration counter-terrorism policies.
But the decision was met with criticism among conservatives and CIA veterans, who warned that the highly detailed documents would serve as a counter-interrogation training manual for Al Qaeda and other terrorist groups.
Former CIA Director Michael V. Hayden said the release of the memos would make the country less safe as enemies learned about techniques that might be approved again in the future.
The documents go beyond cataloging the methods the CIA was authorized to use and spell out in detail how they were to be administered.
Prisoners could be kept shackled in a standing position for as many as 180 hours. The documents also noted that more than a dozen CIA prisoners had been deprived of sleep for at least 48 hours, three for more than 96 and one for the nearly eight-day maximum allowed. Another document seemed to endorse sleep deprivation for 11 days.
In some cases, the memos address specific interrogation plans. When the CIA proposed putting an Al Qaeda suspect in a small box with an insect, the Justice Department endorsed the idea but added conditions it said were necessary to keep the agency from violating the international convention against torture.
"If you do so . . . you must inform him that the insects will not have a sting that would produce death or severe pain," said a 2002 memo sent to the CIA's acting general counsel. A footnote clarified that the CIA never carried out the insect interrogation plan.
The documents include elaborate legal debate over the simulated drowning method known as waterboarding.
A May 10, 2005 memo -- one of several documents that seemed to strain to find a legal rationale for the method -- spelled out that a prisoner could be waterboarded at most six times during a two-hour session. It also required that a physician be on duty in case a prisoner didn't recover after being returned to an upright position.
In that event, "the intervening physician would perform a tracheotomy," the memo said.
The four documents cover a period of time from 2002 until 2005, when the government was recalculating its approach to detention and interrogation matters in the aftermath of the Abu Ghraib prison scandal.
The release of the documents was preceded by months of jostling among CIA and Justice Department officials over how much to disclose.
A department official who was not authorized to speak publicly said Atty. Gen. Eric H. Holder Jr. urged full disclosure to help restore trust in the Justice Department, which had been beleaguered by criticism that it had twisted the law to fit the Bush administration's political ends.
On Wednesday, the department issued a memo repudiating the opinions in the four Bush administration documents, saying they no longer represented the views of the Office of Legal Counsel.
Three of the four memos released Thursday were signed by Steven G. Bradbury, who served as head of the Office of Legal Counsel from 2005 until President Bush left office.