[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2009/POLITICS/04/26/torture.debate/art.capitolday.gi.jpg caption="Some congressional Democrats are calling for an investigation into CIA interrogation techniques."]
WASHINGTON (CNN) - An independent commission is needed to determine who authorized the use of abusive interrogation techniques against suspected terrorists, a leading advocate of such a panel said Sunday.
"I want to know who was it who made the decisions that we will violate our own laws; we'll violate our own treaties; we will even violate our own Constitution," Sen. Patrick Leahy told CBS' "Face the Nation."
"That we don't know," said Leahy, D-Vermont, the chairman of the Senate Judiciary Committee. "We don't know what that chain of command was."
Former President George Bush repeatedly denied that his administration authorized the torture of prisoners in U.S. custody. But a set of legal opinions released earlier in this month documented the Bush administration's justification for coercive interrogation techniques including waterboarding, which has been considered torture since the Spanish Inquisition.
A Senate Armed Services Committee report released last week showed that top Bush administration officials gave the CIA approval to use waterboarding as early as 2002. And in 2003, a meeting that included then-Vice President Dick Cheney, CIA Director George Tenet, Attorney General John Ashcroft and National Security Adviser Condoleezza Rice reaffirmed the use of coercive tactics, according to the Senate Intelligence Committee.
The releases have fueled calls for investigations of former administration and led to arguments from Bush's defenders - including Cheney - that the tactics produced information that saved American lives.
Leahy first proposed the idea of a nonpartisan "commission of inquiry" in March. He said Sunday that he was not "out for some kind of vengeance," but added, "I'd like to read the page before we turn it."