April 16 Four newly released memos issued by the U.S. Justice Department during the Bush administration between 2002 and 2005 spelled out methods that could be used by interrogators on terrorism suspects.
President Barack Obama has now banned use of the methods, some of which were condemned as torture by rights advocates.
Here are some details of the methods as described in the memos:
* This technique induced a sensation of drowning. The detainee would lie face-up and strapped down with his head inclined down. A cloth was placed over his face on which cold water was poured for periods of at most 40 seconds. "This creates a barrier through which it is either difficult or impossible to breathe," one memo said.
Each session could last no more than two hours. "Water may be applied for a total of no more than 12 minutes during any 24-hour period," the memo said.
* Former U.S. President George W. Bush authorized the CIA to use waterboarding in interrogations of senior al Qaeda suspects after the Sept. 11 attacks. It was used against the suspected planner of the Sept. 11 attacks, Khalid Sheik Mohammed, and two others -- senior al Qaeda members Abu Zubaydah and Abd al-Rahim al-Nashiri, the government memos said.
* Human Rights Watch says waterboarding dates at least to the Spanish Inquisition and was also used in Latin America in the 1970s and 1980s.
* Placing an insect into a "confinement box" was sought as a tactic on Zubaydah. He could be kept in a larger box in which he could both stand and sit for up to 18 hours, but would not spend more than an hour at a time in the "smaller" box. Interrogators planned to tell Zubaydah they were putting a stinging insect into the box but it would actually be harmless "such as a caterpillar."
* In "walling," the interrogator would pull a detainee toward him then slam him against a "flexible false wall" in a technique designed to create a loud sound and shock the prisoner. A detainee may be walled once to make a point or 20 to 30 times when interrogation requires "a more significant response to a question."
* Sleep deprivation, in which detainees were shackled in a standing position, was used on more than a dozen detainees for more than 48 hours, on three detainees for more than 96 hours and on one detainee for the maximum allowed of 180 hours.
* Three interrogation techniques are typically used as a starting point to show the detainee has no control over basic human needs. They are "nudity, sleep deprivation (with shackling and, at least at times with use of a diaper), and dietary manipulation," according to one memo. (Reporting by Tabassum Zakaria, James Vicini and David Morgan; Editing by Deborah Charles and Peter Cooney)