A military interrogation expert, U.S. Air Force Col. Steven Kleinman, told Congress on Thursday that he witnessed interrogations of Iraqi detainees that he considers violations of the Geneva Conventions.

One of those interrogations was conducted by a civilian and a contractor employed by his own organization, the Joint Personnel Recovery Agency, which had sent a small team to Iraq in September 2003 to help a special forces task force make its interrogations more effective.

Kleinman told the Senate Armed Services Committee that his two colleagues forcibly stripped an Iraqi prisoner naked, shackled him, and left him standing in a dank, six-foot (1.8 meter) cement cell with orders to the guards that the prisoner was not to move for 12 hours. They could intervene only if he passed out, Kleinman said his two colleagues told the guards.

Had the prisoner passed out, he would have hit his head on a wall, Kleinman said.

Kleinman put a stop to the interrogation. The team returned to the United States several days later.

"Until their time in Iraq they had never seen a real world interrogation," he said.

Kleinman also detailed sitting in on another interrogation. An Iraqi prisoner was on his knees in a room painted all black with a light shining in his face. Behind him stood an American guard slapping an iron bar against his palm. After every question the Iraqi answered, his military interrogators slapped him across the face. That had been going on for 30 minutes.

Kleinman said he called his now retired commander, Col. Randy Moulton, to express his concern about the methods being used. He said Moulton told him the harsh techniques had been specifically approved by the Pentagon's general counsel, William "Jim" Haynes or higher. Moulton also said he had been told the prisoners were terrorists who were not protected by the Geneva Conventions, Kleinman said.