Medical personnel involved in the agency’s first waterboarding effort raised doubts about need for method, in contrast with longstanding CIA claims

Medical personnel who aided in the CIA’s first simulated drowning found that the detainee who endured it was probably willing to cooperate before his torture. They even mocked agency defenses of waterboarding as “creative but circular”, according to an extraordinary declassified document.

In an assessment devastating years of CIA and allied insistences that waterboarding was a critically important intelligence-gathering technique, the undated and heavily redacted document attributed to the chief of the CIA’s Office of Medical Services (OMS), states that detainee Abu Zubaydah’s cooperation with interrogators in 2002 “did not correlate that well with his waterboard sessions”.

The Abu Zubaydah waterboarding was the wellspring from which the CIA’s infamous former torture program, which it refers to euphemistically as “enhanced interrogation”, emerged. Contractor psychologists Bruce Jessen and James Mitchell, now the subject of a federal lawsuit, used it as a test case to implement a program they designed that yielded international human-rights condemnations and an extensive Senate committee inquiry.

Eighty-three times in the span of a month, CIA interrogators subjected Abu Zubaydah to waterboarding, a technique the body processes as drowning-induced suffocation.

But writing in “retrospect”, OMS concluded that Abu Zubaydah “probably reached the point of cooperation even prior to the August [2002] institution of ‘enhanced’ measures – a development missed because of the narrow focus of questioning”.

That OMS conclusion bolsters the account of a former FBI official, Ali Soufan, who interrogated Abu Zubaydah in a secret Thai prison that spring. Soufan would later testify and write in a book, The Black Banners, that the CIA interfered with and ultimately scotched a promising and less-coercive interrogation of Abu Zubaydah – one that the landmark 2014 Senate inquiry found yielded intelligence on al-Qaida.

“Nothing changed in my statement. A lot changed in their statements. Now you know why my statement was the only statement under oath,” Soufan told the Guardian.

“From day one, I mentioned that CIA people who were there were as upset as me and left [the interrogation] before me.”

Joe Margulies, an attorney for Abu Zubaydah, said the document “confirms what we’ve been saying all along and shows what happens when amateurs are given authority over the nation’s security. Mitchell and Jessen were so certain they knew the answer before they asked the question that they couldn’t hear the truth even as Abu Zubaydah gurgled it from the board.”

The OMS official appeared to rebuke a “psychologist/interrogator” who “later said that waterboard use had established that AZ [Abu Zubaydah] had no further information on imminent threats – a creative but circular justification”. Mitchell has admitted to participating in Abu Zubaydah’s waterboarding.

The OMS official stated in the document that “only when questioning changed to subjects on which he had information (toward the end of waterboarding usage) was AZ [Abu Zubaydah] forthcoming.”

In December 2014, John Brennan, the CIA director, responded to the Senate inquiry’s conclusions that torture was ineffective and the agency had misled members of the Bush administration and Congress about its utility by saying it was ultimately “unknowable” whether the agency could have yielded information from detainees without torture.

But the OMS official cited in the document goes further: “In any event, there was no evidence that the waterboard produced time-perishable information which would have been otherwise unobtainable.”

A CIA spokesman referred back to the agency’s 2013 response to a draft of the Senate report. It included the claim: “The Agency takes no position on whether intelligence obtained from detainees who were subjected to [torture] could have been obtained through other means or from other individuals. The answer to this question is, and will remain, unknowable.”

The document, and several others related to the torture program, were declassified on Tuesday after transparency lawsuits filed by Vice News journalist Jason Leopold and the American Civil Liberties Union.

Declassified portions of the Senate intelligence committee’s 2014 report found that Abu Zubaydah, severely wounded after his capture in March 2002, had cooperated with his FBI interrogators from his hospital bed. He identified Khalid Sheikh Mohammed’s role in the 9/11 attacks and provided the FBI with aliases for Mohammed, as well as other information.

But Abu Zubaydah’s CIA captors became convinced that the detainee was withholding information on active terrorist plots against the US – an assessment criticized by OMS in the document, which attributed it to a “narrow focus of questioning”.

The CIA would later falsely assert that Abu Zubaydah had “stopped all cooperation”, according to the Senate report. Senior CIA officials proposed subjecting Abu Zubaydah to a regimen, based on Mitchell and Jessen’s advocacy, of “learned helplessness”, which included waterboarding and other torture techniques. The torture was sufficiently severe that the Senate report found Abu Zubaydah would lie down meekly on the waterboard when his CIA interrogator “snapped his fingers twice”.

A different CIA document also partially declassified on Tuesday, dated weeks before Abu Zubaydah’s waterboarding and cited in the Senate report, stated: “We need to get reasonable assurances that subject will remain in isolation and incommunicado for the remainder of his life.”

The unnamed official explicitly states that the imminent torture could kill Abu Zubaydah and discussed destroying his body.

“In the event the subject dies we need to be prepared to act accordingly keeping in mind the liaison equities involving our hosts. If the subject dies, we plan on seeking … assistance for the cremation of subject.”

Abu Zubaydah, who lost an eye during his CIA captivity, currently resides in the Guantánamo Bay detention facility. Neither the Bush nor Obama administrations have been charged with war crimes.

Once approved by the Bush administration, the CIA treatment of Abu Zubaydah became a template for its torture of at least 118 other detainees, the Senate report documented.

Drawing on years’ worth of declarations by the CIA and its advocates that its torture program prevented attacks – which internal CIA assessments do not support – Donald Trump, the presumptive Republican presidential nominee, has vowed to bring back waterboarding and “worse” torture techniques if elected.

“I think Trump can say whatever he wants to say. I really doubt that he will have people in the government excited to go down this path again,” Soufan said.

Abu Zubaydah attorney Margulies added: “Beware the demagogue who thinks every problem can be solved and every question answered with a good old-fashioned beating.”