Fifteen years after he helped devise the brutal interrogation techniques used on terrorism suspects in secret C.I.A. prisons, John Bruce Jessen, a former military psychologist, expressed ambivalence about the program. He described himself and a fellow military psychologist, James Mitchell, as reluctant participants in using the techniques, some of which are widely viewed as torture. The two psychologists ... are defendants in the only lawsuit that may hold participants accountable for causing harm. Revelations about the C.I.A. practices ... led to an eventual ban on the techniques and a prohibition by the American Psychological Association against members' participation in national security interrogations. The two psychologists argue that the C.I.A., for which they were contractors, controlled the program. But it is difficult to successfully sue agency officials because of government immunity. Under the agency's direction, the two men ... proposed [and applied] the "enhanced interrogation" techniques. Their business received $81 million. When [the psychologists] wanted to end the waterboarding sessions as no longer useful, C.I.A. supervisors ... ordered them to continue. Dr. Mitchell said that the C.I.A. officials told them: "'You guys have lost your spine.' I think the word that was actually used is that you guys are pussies. There was going to be another attack in America and the blood of dead civilians are going to be on your hands."