GUANTANAMO BAY NAVY BASE, Cuba -- On the eve of the resumption of its war crimes trials, the military on Sunday unveiled a new state-of-the-art court capable of trying six alleged terrorists simultaneously -- and silencing them from the outside world, if they try to spill state secrets.

The military offered a comprehensive look at its new court, part of a $12 million razor-wire-ringed legal complex that arrived by cargo plane and barge in prefabricated parts. Unlike a more ambitious plan to build a $125 million compound on the site overlooking Guantánamo Bay, the new compound can be dismantled and shipped back stateside once trials are done.

''We got it up in six months at a fraction of the cost,'' said Army Col. Wendy Kelly, director of operations at the Pentagon's Office of Military Commissions.

Architecturally, the bunker-style building is a bland structure impenetrable to electronic eavesdropping.

Inside, it has an up-to 20-seat jury box for the U.S. military officers who will be assembled from around the world, case by case, to sit in judgment; typical judges and prosecution tables, plus a bank of defense tables where six captives can sit at computers on faux leather chairs, unshackled but guarded by soldiers.

KILLING THE SOUND

It also has a 30-seat adjacent room, behind a tempered-glass window, where observers can hear the proceedings on a broadcast basis -- and a kill-switch where a security officer or the judge can cut the sound in case someone divulges a state secret.

There is no blackout capacity or curtain, meaning the media, legal observers, dignitaries and family members who might attend a trial could watch but not listen.

Such measures could be necessary if the Pentagon presses ahead with plans to try alleged 9/11 architect Khalid Sheik Mohammed or any of the other 14 high-value detainees who arrived at this base in September 2006 from three-plus years of secret CIA custody.

The agency has classified the interrogation techniques it used on the men -- in secret sites, somewhere overseas -- as national security secrets. Were one to blurt out his treatment at trial, the judge or security officer could simply stifle their voices.

It is inside razor wire along with five separate windowless cells where lawyers can meet clients who could some day include the alleged architects of the 9/11 attacks and other suspected senior al Qaeda leaders.

On Monday, lawyers return to the old court to argue, again, for dismissal of terror charges against Guantánamo's youngest detainee, Toronto-born Omar Khadr, who was captured at age 15 in Afghanistan. Khadr's Pentagon-appointed attorneys argue before an Army judge Monday that all war crimes charges should be dismissed against the Canadian man, now 21.

He is charged in the grenade killing of a U.S. Army medic, Sgt. 1st Class Christopher Speer, 28, of Albuquerque, N.M., who was part of a Special Forces unit that attacked a suspected al Qaeda compound in Khost, Afghanistan, in July 2002.

Khadr is from a fundamentalist Muslim family, which sometimes celebrated Muslim feasts with the bin Ladens in Afghanistan, and he is also accused of conspiring with and supporting al Qaeda, attempted murder of other members of Speer's unit and spying by scouting on U.S. forces.

Conviction could carry life in prison because, in consideration of his youth, the Pentagon waived an option to seek the death penalty.

Khadr's lawyers claim he should have been treated as a ''child soldier,'' not equally responsible to an adult, in part because he was 15 at the time of his capture.

''If jurisdiction is exercised over Mr. Khadr, the military judge will be the first in Western history to preside over the trial of alleged war crimes committed by a child,'' Navy Lt. Cmdr. William Kuebler wrote in a 15-page motion.

Moreover, Kuebler argued that the United States failed his client -- who has grown into beefy, bearded adulthood behind the razor wire here at Camp Delta.

But the chief prosecutor, Army Col. Larry Morris, disputes the defense characterization of the captive as a child soldier -- saying Khadr did not meet the definition under international law.

''The conventions on child soldiers establish the minimum age for conscripting soldiers,'' he said in a statement, adding, ``They do not provide amnesty for war crime activities on the battlefield.''

DETAINED SINCE 16

Khadr arrived at this remote prison camp at age 16, saw his first attorneys two years later and has periodically fired the lawyers who have volunteered to work on his case.

He has spent long portions of detention in special segregation for war-court candidates but more recently was moved to a POW-style compound where about 60 of the 275 or so detainees live in communal bunkhouses.