WASHINGTON — A Senate investigation concludes that waterboarding and other harsh interrogation methods provided no key evidence in the hunt for Osama bin Laden, according to congressional aides and outside analysts familiar with a still-secret 6,200-page report. The finding could deepen the worst rift in years between lawmakers and the CIA.
The CIA disputes the conclusion and already is locked with the Senate intelligence committee in an acrimonious fight amid dueling charges of snooping and competing criminal referrals to the Justice Department.
The public may soon get the chance to decide, with the congressional panel planning to vote Thursday to demand that a summary of its review be declassified.
From the moment of bin Laden’s death almost three years ago, former Bush administration figures and top CIA officials have cited the evidence trail leading to the Al Qaeda mastermind’s walled Pakistani compound as vindication of the ‘‘enhanced interrogation techniques’’ they authorized after the Sept. 11, 2001, attacks.
But Democratic and some Republican senators have called that account misleading, saying that simulated drownings, sleep deprivation, and other such practices were cruel and ineffective.
The intelligence committee’s report, congressional aides and outside experts said, backs up that case after examining the treatment of several high-level terror detainees and the information they provided on bin Laden. The aides and people briefed on the report demanded anonymity because they weren’t authorized to speak publicly about the confidential document.
The most high-profile detainee linked to the bin Laden investigation was Khalid Sheikh Mohammed, the accused 9/11 organizer, who was waterboarded 183 times. Mohammed, intelligence officials have noted, confirmed after his 2003 capture that he knew an important Al Qaeda courier with the nom de guerre Abu Ahmed al-Kuwaiti.
The Senate report concludes that such information wasn’t critical, according to the aides. Mohammed only discussed Kuwaiti months after being waterboarded, while he was under standard interrogation, they said. And Mohammed neither acknowledged Kuwaiti’s significance nor provided interrogators with the courier’s real name.
The debate over how investigators put the pieces together is significant because years later, the courier led US intelligence to the sleepy Pakistani military town of Abbottabad. There, in May 2011, Navy SEALs killed bin Laden in a secret mission.
The CIA also has pointed to the value of information provided by senior Al Qaeda operative Abu Faraj al-Libi, who was captured in 2005 and held at a secret prison run by the agency.
In previous accounts, US officials have described how Libi made up a name for a trusted courier and denied knowing Kuwaiti. Libi was so adamant and unbelievable in his denial that the CIA took it as confirmation that he and Mohammed were protecting the courier.
The Senate report concludes that evidence gathered from Libi wasn’t significant either, aides said.
Essentially, they argue, Mohammed, Libi, and others subjected to harsh treatment confirmed only what investigators already knew about the courier. And when they denied the courier’s significance or provided misleading information, investigators would only have considered that significant if they had already presumed the courier’s importance.
The aides did not address information provided by yet another Al Qaeda operative, Hassan Ghul, who was captured in Iraq in 2004. Intelligence officials have described Ghul as the true linchpin of the bin Laden investigation after he identified Kuwaiti as a critical courier.