At an arraignment scheduled for Thursday, Khalid Sheikh Mohammed was expected to make his first public appearance since being captured in Pakistan in 2003, held in CIA custody at secret sites and transferred to Guantanamo in 2006.

Air Force Brig. Gen. Tom Hartmann, a top tribunal official, told dozens of journalists late Wednesday he expects defense lawyers will robustly argue points with prosecutors and Judge Ralph Kohlmann on behalf of their clients, who face the death penalty.

"Expect to see challenges tomorrow, and the intensity of the process," Hartmann said at a briefing in an abandoned aircraft hangar near the courthouse at this isolated U.S. Navy base.