In painful detail, the declassified portions of the Senate Intelligence Committee’s report on the CIA’s former detention and interrogation program erase any doubt that the United States systematically tortured prisoners in its custody. Too many people who should have known better violated our nation’s most sacred laws and values. Why? Because doing so was necessary to save lives, we were told. For years, torture’s apologists sold that story without having to prove it. “Classified,” they would claim, “but if you only knew what we know  . . . ”

The truth is finally starting to come out, and their narrative is crumbling.

Recently, in a rare public news conference, CIA Director John O. Brennan addressed the committee’s report. Amidst an expected defense of the agency, and at least some recognition that internal reforms are necessary, he made an eye-opening comment:

“But let me be clear. We have not concluded that it was the use of [enhanced interrogation techniques] within [the detention and interrogation] program that allowed us to obtain useful information from detainees subjected to them. The cause and effect relationship between the use of EITs and useful information subsequently provided by the detainee is, in my view, unknowable.”

That is a stunning admission, and one of enormous consequence.

Of course, torture is illegal and immoral under any circumstance — it should not matter whether it ever “works”. Unfortunately, questions about torture’s necessity and efficacy occupy a unique space in the context of the CIA program. Justice Department lawyers who authorized it relied repeatedly on CIA claims that torture successfully produced not just “useful information,” but unique, otherwise unobtainable intelligence that disrupted terrorist plots and saved thousands of lives.

For example, a 2005 memo to the CIA from the Office of Legal Counsel concluding that “enhanced interrogation” did not violate the Convention Against Torture states: “You have informed us that the CIA believes that enhanced interrogation techniques remain essential to obtaining vital intelligence necessary to detect and disrupt such emerging threats. In particular, the CIA believes that it would have been unable to obtain critical information from numerous detainees, including KSM and Abu Zubaydah, without these enhanced interrogation techniques.”

A 2007 memo, finding that “enhanced interrogation” was permissible under the War Crimes Act, the Detainee Treatment Act, and Common Article 3 of the Geneva Conventions similarly noted the OCL’s “understand[ing] that use of enhanced interrogation techniques has produced significant intelligence that the government has used to keep the nation safe.” More specifically, “[t]he techniques have revealed plots to blow up the Brooklyn Bridge and to release mass biological agents in our nation’s largest cities.”

The Senate Intelligence Committee concluded such claims were false. Apparently so, too, did the CIA — years ago in an internal review of the “enhanced interrogation” program that remains secret. Last week, Sen. Mark Udall took to the Senate floor to shed additional light on the CIA’s own analysis of the very same trove of documents that underlies the report.

It is “a smoking gun”, he said of the so-called Panetta Review. It “[f]ound that the CIA repeatedly provided inaccurate information to the Congress, the President, and the public on the efficacy of its coercive techniques.” It “identifies dozens of documents that include inaccurate information used to justify the use of torture and indicates that the inaccuracies it identifies do not represent an exhaustive list.” It describes “how detainees provided intelligence prior to the use of torture against them;” “how the CIA tortured detainees even when less coercive methods were yielding intelligence;” and “how the CIA, contrary to its own representations, often tortured detainees before trying any other approach.” Finally, Udall explained, the Panetta Review shows that “CIA personnel tortured detainees to confirm they didn’t have intelligence, not because they thought they did.”

So, without any firm evidence that doing so was either necessary or effective, the CIA deprived captives of sleep for up to 180 hours, often standing or in stress positions and sometimes with their hands shackled above their heads. It abused two men this way who had broken feet. It subjected others to “rectal rehydration and feeding” — a procedure that might more accurately be characterized as rape. It caused men to hallucinate. Threatened to slit one captive’s mother’s throat. Waterboarded another to the point that he became “completely unresponsive, with bubbles rising through his open, full mouth.” Froze a man to death.

In response to questions during his news conference, Brennan said the CIA has no intention of getting back into the detention business or resurrecting the “enhanced interrogation” program. That is a welcome statement, but hardly reassuring. Congress should legislate to make sure this never happens again.

David Irvine is a Salt Lake City attorney in private practice, a former Republican state legislator and a retired Army brigadier general. He is also a member of The Constitution Project’s Task Force on Detainee Treatment, which published the bipartisan Detainee Treatment Report in 2013.