A top U.S. adviser on terrorism has publicly denounced the interrogation technique of “waterboarding” as a form of torture. On Wednesday, Malcolm Nance said he had witnessed hundreds of waterboarding exercises while working at the U.S. departments of Homeland Security, special operations and intelligence. Nance says the practice is taught at a U.S. Navy training facility in San Diego. Waterboarding simulates the experience of drowning by strapping a victim to a board and forcing water into their lungs through a cloth covering the face. Attorney general nominee Michael Mukasey is facing a potential rejection from the Democrat-controlled Senate over his waterboarding stance. Mukasey said this week he does not know if waterboarding amounts to torture. Legal experts interviewed by The New York Times say Mukasey’s evasive response could be a deliberate attempt to avoid laying ground for prosecutions against U.S. officials who have practiced waterboarding. Mukasey’s nomination goes before the Senate next week.