Previously undisclosed Justice Department e-mail messages, interviews and newly declassified documents show that some of the lawyers, including James B. Comey, the deputy attorney general who argued repeatedly that the United States would regret using harsh methods, went along with a 2005 legal opinion asserting that the techniques used by the Central Intelligence Agency were lawful.
The main authors of memorandums authorizing the methods — John C. Yoo, Jay S. Bybee and Steven G. Bradbury — have been widely pilloried as facilitators of torture.
Others, including Mr. Comey, Jack Goldsmith and Daniel Levin, have largely escaped criticism because they raised questions about interrogation and the law.
The lawyers had to interpret a 1994 antitorture law written largely with despotic foreign regimes in mind, but used starting in 2002, in effect, as a set of guidelines for American interrogators. The law defined torture as treatment "specifically intended to inflict severe physical or mental pain or suffering." By that standard, a succession of Justice Department lawyers concluded that the C.I.A.'s methods did not constitute torture.
The only issues that provoked debate were waterboarding, which Mr. Goldsmith questioned, and some combinations of multiple techniques, which Mr. Comey resisted.