The first detailed accounts of the brutal interrogation program the Central Intelligence Agency established after the Sept. 11 attacks noted that psychologists and other medical professionals played key roles in abetting the torture of terrorism suspects. However, much about their role and their degree of responsibility in one of the most macabre and shameful chapters of American history has remained shrouded in secrecy.

A new report by a former federal prosecutor, first disclosed by James Risen in The Times, contains astonishing, disturbing details. It found that top members of the American Psychological Association, the largest professional organization of psychologists, colluded with officials at the Pentagon and the C.I.A. to keep the group’s ethics policies in line with tactics that interrogators working for the agency and the military were employing.

At a time when intelligence and Department of Defense officials were desperate for intelligence that would help them foil new terror plots, they were willing to pay handsomely for experts who could give the torture program a veneer of legitimacy. Prominent psychologists were apparently happy to indulge them. “A.P.A. chose its ethics policy based on its goals of helping D.O.D., managing its P.R., and maximizing the growth of the profession,” the report said.