Abu Zubaydah was captured by US forces after a gun fight in Faisalabad, Pakistan, in March 2002.
US officials incorrectly believed the Saudi Arabian citizen was a member of al-Qaida and transported him to a secret US-run prison, known as a black site, in Thailand.
In August 2002, Zubaydah, already suffering from a severe leg wound, became the first victim of the George W. Bush administration's "enhanced interrogation," which included shackling him in stress positions and confined spaces, prolonged sleep deprivation, and 83 episodes of waterboarding.
The Senate Intelligence Committee's report on the CIA torture program, which was partially declassified and released in 2014, found the enhanced-interrogation techniques were ineffective, "brutal," and "far worse" than the CIA had described them as being.
During one waterboarding session, Zubaydah "became completely unresponsive, with bubbles rising through his open, full mouth."
At some point during Zubaydah's detention, he lost one of his eyes for unknown reasons.
CIA interrogators were so worried about the details of Zubaydah's torture becoming public that they requested "reasonable assurances that [Abu Zubaydah] will remain in isolation and incommunicado for the remainder of his life," the Senate report found.
Investigators found that the CIA lied to Bush about the effectiveness of the enhanced-interrogation techniques used on Zubaydah, telling the president that Zubaydah gave interrogators additional information as a result of the torture.
In fact, the report found that Zubaydah, now 48, provided the CIA with more information about al-Qaida "activities, plans, capabilities, and relationships," and the group's leadership before being subjected to torture than he did after.
And they discovered that Zubaydah was never a member of al-Qaida, didn't have advanced knowledge of the 9/11 attacks, and had no information about future attacks.