GUANTANAMO BAY NAVY BASE, Cuba — The military commission hearing the first U.S. war crimes tribunal since World War II took secret testimony on Thursday, a first.

Defense lawyers called U.S. Army psychologist Col. L. Morgan Banks III to testify, then all sides agreed that what he was about to say at the trial of Osama bin Laden's driver was secret.

So reporters were ushered out of the commissions room, as were observers from the American Civil Liberties Union and Human Rights Watch.

The accused, Salim Hamdan, 37, of Yemen, was allowed to remain.

Banks is a clinical psychologist with the Special Operations Command at Fort Bragg, the home of Delta Force. In 2003, he was identified as the senior Army Survival, Evasion, Resistance, and Escape (SERE) psychologist, in a program that teaches troops how not to crack under enemy interrogation.

On Thursday the public could only listen to the colonel as he swore to tell the truth and to learn that after the Sept. 11, 2001, attacks he was assigned to special duties at the Pentagon's Central Command.

Centcom, in Tampa, directed the invasion of Afghanistan, where Hamdan was captured in November 2001.

''I would note for the record that it is not the defense that has requested this closed session,'' said Navy Lt. Cmdr. Brian Mizer, Hamdan's Pentagon-appointed attorney. "It is necessary, according to the government, to protect the information.''

The drama took place in the older of the two war court chambers, built in an abandoned air traffic control tower. The audio was instantly cut to a news media center at a nearby ramshackle air hangar, where reporters monitor the trials.

At the media center, a flat screen on the wall showed Banks' lips moving and hands gesturing under questioning first by Mizer and then by a case prosecutor, Air Force Maj. Omar Ashmawy. There was no sound.

Much of the ninth day of the driver's trial was shrouded in secrecy.

Earlier, the war court clerk released a five-page ruling from Hamdan's judge, Navy Capt. Keith Allred, with three pages blacked out entirely by a national security censor.

Four full paragraphs remained, and portions of two others.

At issue was whether to allow testimony from a federal agent who interrogated the driver in March 2003. Defense lawyers claimed that, based on a partial release of prison camp records, Hamdan was isolated and subjected to sleep deprivation before the interrogation.

''Being detained in Guantanamo Bay is undoubtedly an unpleasant, highly regimented experience, with instant rewards or loss of privileges for infractions,'' the judge concluded.

But three and a half pages — including the entire section called ''findings of fact,'' which supported his thesis — were hidden beneath black.