Military court proceedings for four detainees from the US-led war in Afghanistan have started at the US naval base in Guantanamo Bay, Cuba.
Almost 600 detainees are held at Guantanamo
The men - two Yemenis, a Sudanese and an Australian, David Hicks - are the first to face such trials, which have not been used for more than 50 years.
Salim Ahmed Hamdan, 34, from Yemen and Osama Bin Laden's former driver, was the first to appear.
He postponed entering a plea to the charge of conspiracy to commit murder.
He appeared without handcuffs or chains, wearing a long white robe and tan suit, listening attentively to an Arabic translation of the proceedings and occasionally smiling.
David Hicks, 29, will appear before the commission on Wednesday. He also faces charges of attempted murder.
Two years to trial
Mr Hamdan's military-appointed lawyer, Lt Cmdr Charlie Swift, questioned the suitability of four members of the panel judging him, saying they had personal connections with the 9/11 attacks and the "war on terror" that could lead them to be biased.
He said Mr Hamdan, who denies terrorism, should have had the chance to contest his status as "enemy combatant" in a US civilian court.
Ali Hamza Ahmad Sulayman al Bahlul, 33, also from Yemen, and Ibrahim Ahmed Mahmoud al Qosi, born in 1960, of Sudan, will appear later in the week.
All four men are believed to have been apprehended in Afghanistan sometime in 2001 or 2002. They have been at Guantanamo Bay for more than two years.
Those among the 590 detainees at Guantanamo Bay who have been designated enemy combatants are ordered to undergo trial by military commission.
They are the first such legal proceedings held by the Americans since the aftermath of World War II.
Security is tight and only eight journalists are being allowed inside the tribunal room at any one time. Others can watch from a monitoring room.
David Hicks is due to go on trial on Wednesday
Five senior military officers are sitting on the commissions. Prosecution and defence attorneys also come from the armed forces.
The trials have come under fire with human rights groups saying the process is illegal. Amnesty International expressed concern on Tuesday that it was being denied access to key participants, including the presiding officer.
A spokesman for the prosecution said the military commissions met international standards for full and fair trials.
The government says US civilian courts have no jurisdiction over enemy detainees, but lawyers' groups and human rights activists argue that the men held at Guantanamo Bay are being denied their legal rights under the US constitution.