A heavily redacted version was released last year. More than 35 pages of the 109-page report are almost entirely blacked out.
The report indicates the CIA's interrogation programme yielded intelligence that led to the capture of other terrorist suspects and warned of terror plots against the US and elsewhere. But the assessment comes with a caveat.
"The effectiveness of particular interrogation techniques in eliciting information that might not otherwise have been obtained cannot be so easily measured, however."
The report comes as US attorney general Eric Holder ordered a special investigation into CIA agents who may have gone too far in interrogation of al-Qaida and other suspects taken after the 9/11 attacks.White House spokesman Robert Gibbs released a statement on the inquiry, saying: "The president has said repeatedly that he wants to look forward, not back, and the president agrees with the attorney general that those who acted in good faith and within the scope of legal guidance should not be prosecuted." He added: "Ultimately, determinations about whether someone broke the law are made independently by the attorney general."
The report reveals for the first time harsh interrogation techniques, and discusses the agency's use of waterboarding, "walling", mock execution, menacing a prisoner with a power drill, and other practices. The report acknowledges that interrogators used techniques they knew had not been approved by US government lawyers.
The still heavily-blacked out report shows that an interrogator told Abd al-Rahim al-Nashiri, a Saudi accused of planning the 2000 attack on the USS Cole in Yemen, "we could get your mother in here", and "we can bring your family in here". The report indicates that an unidentified interrogator spoke an Arabic dialect that would lead al-Nashiri to believe he was part of a security service known for "sexually abusing female relatives in front of the detainee".
Another interrogator told Khalid Sheikh Mohammed, the self-professed mastermind of the September 11 attacks, that his captors would kill his children "if anything else happens in the United States".
Knowing it was not specifically approved by justice department attorneys, an interrogator scraped al-Nashiri with "the kind of brush one uses in a bath to remove stubborn dirt", which cut and bruised the detainee.
In another newly revealed technique, the report says that interrogators pressed their fingers into a detainee's carotid artery in order to constrict the flow of blood to his brain. The interrogators "watched his eyes to the point that the detainee would nod and start to pass out, then ... shook the detainee to wake him."
The process was repeated three times. An interrogator acknowledged to the inspector general that he "laid hands on the detainee and may have made him think he was going to lose consciousness".
The report reveals new details of a mock execution intended to frighten a detainee into believing he was next in line for killing. Interrogators fired a handgun outside a prisoner's cell while agents screamed and yelled.
"When the guards moved the detainee from the interrogation room, they passed a guard who was dressed as a hooded detainee, lying motionless on the ground, and made to appear as if he had been shot to death," the report reads. A CIA officer later said the show was "transparently a ruse" and was thus ineffective. However, the report states that one detainee "sang like a bird" after witnessing the "body".
The report also accuses a CIA contractor of beating a prisoner with a large metal flashlight during June 2003 interrogation sessions. The prisoner, who had turned himself in at the urging of a local leader, died in custody four days after his capture. His body was returned to his family with an autopsy being performed.
In July 2003, an officer assaulted a teacher at an Afghanistan religious school when the officer was seeking information about a bomb that killed eight border guards.
The report states that the teacher "smiled and laughed inappropriately", leading the CIA officer to strike him with the butt of his rifle and knee him in the torso several times, all in front of 200 students. The teacher was not seriously hurt, and the agency subsequently returned the officer to the US.
Documents released with the report indicate CIA officers were cleared to force detainees to wear diapers for up to three days at a time, but the report does not specify if the technique was ever used.
The report indicates that the CIA officers involved in the enhanced interrogations were aware they could eventually be prosecuted for war crimes, and one officer feared the programme would be exposed in the news media.
"Ten years from now we're going to be sorry we're doing this," the officer told investigators, but "it has to be done".
