A dozen years after the terrorist attacks of Sept. 11, 2001, an independent, nonpartisan panel’s examination of the interrogation and detention programs carried out in their aftermath by the Bush administration may seem to be musty old business. But the sweeping report issued on Tuesday by an 11-member task force convened by the Constitution Project, a legal research and advocacy group, provides a valuable, even necessary reckoning.

The work of the task force, led by two former congressmen — Asa Hutchinson, a Republican, who served in the Bush administration as under secretary of the Department of Homeland Security, and James Jones, a Democrat, who was an ambassador to Mexico during the Clinton years — is informed by interviews with dozens of former American and foreign officials, as well as with former prisoners.

It is the fullest independent effort so far to assess the treatment of detainees at Guantánamo Bay, in Afghanistan and Iraq, and at the C.I.A.’s secret prisons. Those who sanctioned the use of brutal methods, like former Vice President Dick Cheney, will continue to defend their use. But the report’s authoritative conclusion that “the United States engaged in the practice of torture” is impossible to dismiss by a public that needs to know what was committed in the nation’s name.

The report found that those methods violated international legal obligations with “no firm or persuasive evidence” that they produced valuable information that could not have been obtained by other means. This blunt language should help end a corrosive debate that has broken down on largely partisan lines.