(dpa) - Legal proceedings against Khalid Sheikh Mohammed and four co-defendants in the September 11, 2001, terrorist attacks are set to begin Thursday in Guantanamo Bay, Cuba.
Mohammed, the alleged mastermind of the attacks, had been held in a secret CIA prison after his capture in March 2003, before his transfer in September 2006 to the Guantanamo Bay military prison along with the four other men.
All five could face the death penalty if convicted under the military commissions ordered by US President George W Bush for trying suspects in the war on terrorism.
The defendants will be tried together on 169 counts that include conspiracy, murder in violation of the law of war, attacking civilians and civilian objects, and terrorism. Other charges include causing serious bodily injury, destruction of property and providing material support for terrorism.
The four other defendants are Ramzi bin al-Shibh, the alleged point of contact between the hijackers and al-Qaeda's leadership, Walid bin Attash, believed to have trained some of the hijackers, Ali Abd al-Aziz Ali, Mohammed's nephew and alleged deputy, and Mustafa Ahmed al-Hawsawi.
The five men are being held at a secret location at the US Navy base at Guantanamo, separately from the facility holding lower-level detainees.
Nineteen hijackers commandeered four airliners to strike two towers of the World Trade Center in New York and the Pentagon outside Washington. A fourth plane crashed in Pennsylvania. The attacks killed 2,973 people.
The death penalty cases are likely to intensify criticism of the military commissions, which have been challenged in court. Civil rights advocates have raised questions about the fairness of the tribunals.
Each defendant will be entitled to military defence lawyers and could also hire civilian attorneys. Presiding judges will determine what type of evidence can be used, including information obtained through harsh interrogation methods like water-boarding. The CIA has admitted that it used the technique, which simulates drowning, while questioning Mohammed.
The Pentagon in May announced that charges against Mohammed al- Qahtani, who has been held at Guantanamo, were dropped. No reason was given.
Al-Qahtani was believed to be the 20th hijacker but was stopped while trying to enter the United States before the attacks. He was later captured in Afghanistan.
There is no facility at Guantanamo Bay for carrying out executions, and it remains unclear how the Pentagon would proceed to hand out a death sentence. The US military has not executed anyone since 1961.