The Saudi man charged with bombing the USS Cole in 2000 appeared before a military court at Guantanamo Bay, Wednesday.
Abd al-Rahim al-Nashiri is suspected of organizing the attack. The bombing killed 17 American sailors and injured 39 others.
The attack took place while the Navy destroyer was refueling in Yemen.
Al-Nashiri, 46, was held in secret confinement for nine years.
Authorities said he took orders directly from Osama bin Laden and also set up the October 2002 bombing of the French supertanker MV Limburg and a failed attack of the USS The Sullivans.
He faces the death penalty.
In Wednesday's court appearance, al-Nashiri was allowed to stay unshackled. He declined an offer to exchange his prison uniform for regular clothes during court appearances.
A half-dozen relatives of sailors killed in the Cole bombing traveled to Guantanamo to observe the arraignment. One of them, John Clodfelter, said the prisoner seemed "cocky."
The suspects lawyers said al-Nashiri was subjected to harsh interrogation that amounted to torture, and thus, should receive a lesser sentence.