Sun sets over Camp Justice and its adjacent tent city, legal complex of US Military Commissions, at Guantanamo Bay US Naval Base, 04 Jun 2008

Five men accused of plotting the September 11, 2001 terrorist attacks on the United States will appear before a military tribunal Thursday at the detention center in Guantanamo Bay, Cuba.

Khalid Sheikh Mohammed, the alleged mastermind of the attacks, and four other men will stand before a military judge and hear the charges brought against them. All five men are facing the death penalty if convicted.

The defendants were all held for a number of years in secret CIA detention centers overseas before they were transferred to the U.S. naval base in 2006.

Human rights groups have criticized the military tribunals, saying they violate the defendants' rights because of secret evidence being used against them. But Brigadier General Thomas Hartmann, the tribunal's senior officer, says the suspects will be allowed to put on a full defense against the charges.

The military tribunals were established by the Bush administration as an alternative to the U.S. federal court system, in part because of the secret evidence.

But the original system for the tribunals was ruled by as unconstitutional by the U.S. Supreme Court in 2006. The Bush administration pushed for a new system that was approved by the U.S. Congress, but the Supreme Court is considering another case which could invalidate the revised process.

None of the 275 detainees at Guantanamo have been tried before. A case against an Australian detainee, David Hicks, was resolved when Hicks reached a plea agreement with prosecutors that allowed him to serve a nine-month prison sentence in his native country.

Some information for this report was provided by and Reuters.