A 1989 report from the CIA to Congress stated that “inhumane physical or psychological techniques are counterproductive." Chip Somodevilla/Getty Images

For decades, experts and government officials alike have said torture is not only illegal but also -- more to the point -- does not work. But that didn't stop the CIA from subjecting dozens of detainees to hours of waterboarding, rectal feeding, sleep deprivation and other brutal treatment in the wake of the Sept. 11, 2001, terrorist attacks. The spy agency's insistence on using so-called enhanced interrogation techniques in an attempt to force answers from terror suspects has raised questions about why U.S. officials were so committed to such harsh tactics long after it was known they didn't work.

The CIA has long conceded that torture is ineffective. A 1989 report from the agency to Congress stated that “inhumane physical or psychological techniques are counterproductive because they do not produce intelligence and will probably result in false answers.” The report by the Senate Select Committee on Intelligence released Tuesday reached the same conclusion. But it also revealed that these very methods, discredited by the CIA itself, were the underpinnings of the agency’s former Detention and Interrogation Program between 2002 and 2007.

Clinical psychologist Roy Eidelson, who studies conflict, said all humans are susceptible to violent impulses and a desire for revenge, particularly when the adversary is publicly dehumanized, which was the case after the 9/11 attacks. “You’re not talking about people at that point. It becomes easier to torture. The natural human resistance to such activities diminishes and I’m confident that’s part of what happened,” Eidelson said in a telephone interview, adding that it only becomes easier for a person to continue torturing over time. “The first panicked screams of someone who’s being waterboarded are more stunning to the abuser when they hear it for the first time than when they’ve heard it for the tenth, twentieth or hundredth time. We tend to lose our sensitivity that way.”

The CIA's interrogation program and its enhanced interrogation techniques were authorized by then-President George W. Bush and deemed lawful by the Department of Justice, with an objective to destroy the al Qaeda terrorist group that perpetrated 9/11. The lengthy Senate report from Democratic lawmakers found that harsh interrogation of CIA detainees did not substantially help in tracking down Osama bin Laden, foiling terrorist plots or capturing terrorists. In fact, the Senate report found these methods lead to false information because detainees were willing to say anything to stop the torture, and any intelligence that was generated could have been done so by using more-humane techniques.

CIA officials acknowledged “shortcomings” and “mistakes” in the program, but defended the use of so-called enhanced interrogation techniques on terrorist suspects, which are meant to instill a sense of hopelessness and despair. “Our review indicates that interrogations of detainees on whom [enhanced interrogation techniques] were used did produce intelligence that helped thwart attack plans, capture terrorists, and save lives,” said CIA director John Brennan.

Eidelson said the CIA's defense is partly a means of psychological justification and moral disengagement. “I would think the people in charge of the program want to believe that they saved lives. Psychologically, that’s far more comfortable than the alternative,” said Eidelson, who studies and writes about psychological issues -- including torture -- in political organizational settings. “They don’t use the term ‘torture,’ for example. They called it ‘enhanced interrogation techniques,’ so that they don’t have to every minute think that what they’re doing is torturing.”

Glenn Carle, who served 23 years in the CIA’s National Clandestine Service, said the agency had never been tasked with interrogating before. “I was appalled by the whole process," he said in a telephone interview. "I had worked terrorism issues for years. I was as eager and determined as anybody to stop al Qaeda and get the people who perpetrated 9/11."

The interrogation program appeared to be, in part, unethical experimentation on unwilling subjects to research which coercive methods might work, Eidelson said, adding that government officials at the time were potentially unaware of the 1989 report. Data was carefully collected from each session of waterboarding, for example. “In a sense, there was a future-oriented aspect to this. The CIA did not know what effect waterboarding or sleep deprivation had on detainees. You might continue using these methods, even though they weren’t providing actionable intelligence. There’s still data that, in theory, could be used in the future to better design other coercive techniques,” he said in a telephone interview. “It’s a very ugly thing.”

John Yoo, who served as the Deputy Assistant U.S. Attorney General in the Office of Legal Counsel during the Bush administration, co-authored the secret memorandum allowing for the CIA program in 2002. The memorandum narrowly defined torture and American habeas corpus requirements, asserting the Geneva Convention did not apply to detainees from the war in Afghanistan. The memorandum also asserted the president had the power to take preemptive action against terrorists or states that harbor them, regardless of their connection to the 9/11 attacks, according to the New York Times.

“My guess is that some people at the CIA believe that some form of torture or enhanced interrogation does work — that it has produced actionable intelligence,” Evan Thomas, a journalist and author of a book on the CIA’s early days, wrote in an email to International Business Times.

It's unclear if the CIA will continue to torture terror suspects. While the program was terminated under Bush and deemed illegal under President Barack Obama in 2009, there are still loopholes, said David Schanzer, a public policy professor at Duke University and co-director of the Triangle Center on Terrorism and Homeland Security. “The definition of war crimes could be tightened up to make it absolutely clear that coercive interrogation techniques that use violence are not permissible and are crimes. That’s the ultimate deterrent,” Schanzer said.

Democratic Sen. Diane Feinstein, the Senate committee’s chairman who led the report’s release, had little sympathy for the CIA this week, blatantly deeming the techniques “torture."

“I can understand the CIA’s impulse to consider the use of every possible tool to gather intelligence and remove terrorists from the battlefield, and the CIA was encouraged by political leaders and the public to do whatever it could to prevent another attack,” Feinstein wrote in a foreword to the report. “Nevertheless, such pressure, fear and expectation of further terrorist plots do not justify, temper or excuse improper actions taken by individuals or organizations in the name of national security.”