A former Bush administration official is set to testify Wednesday as Senate Democrats hold a hearing into the use of harsh interrogation techniques.
As a top adviser to Secretary of State Condoleezza Rice, Philip Zelikow argued against the use of waterboarding and other enhanced techniques.
In a 2005 memo, he said some of the tactics violated the constitution's ban on cruel and unusual punishment.
Zelikow recently wrote on Foreign Policy magazine's Web site that the White House tried to collect and destroy every copy of his memo.
Judiciary Committee Chairman Patrick Leahy told the hearing that the "rule of law in the United States means no one is above the law ... not anyone in this room and not the president of the United States."
"The American people deserve to know what mistakes were made and what we intend to do about it,"
Republican Sen. Lindsey Graham told Wednesday's hearing that the attacks of Sept. 11, 2001, left the country "rattled," and the Bush administration "did some things that aren't going to make us safer in the long run."
"The fact we embrace the rule of law is a strength not a weakness," Graham said.