Khalid Sheikh Mohammed and four others who say they planned the 9/11 attacks on New York and Washington appear in a military court charged with murdering 2,976 people.
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The self-described leader of al-Qaeda's military committee previously said the men would plead guilty and welcome the death penalty and martyrdom, but the military court is unlikely to ask them for pleas immediately. On Saturday, the defendants are likely to hear the charges against them so the judge can ensure they understand their rights. Procedural issues will follow.
New rules adopted by Congress forbid the use of testimony obtained through cruel treatment or torture, complicating prosecution efforts as Mohammed was waterboarded by interrogators 183 times in 2003.
Human rights groups and defence lawyers say the reforms banning torture have not gone far enough and that the restriction on legal mail and the overall secret nature of Guantanamo makes it impossible to provide an adequate defence.
Families in Cuba
Relatives of those killed in the attacks are to travel to Guantanamo to witness Mohammed's long-delayed hearing and testimony. The trial is the first time he will appear in public in three years.
"I'm not looking forward to ending someone else's life and taking satisfaction in it, but it's the most disgusting, hateful, awful thing I ever could think of if you think about what was perpetrated," said Cliff Russell, whose firefighter brother Stephen died in the attacks.
This is the second attempt by US officials to prosecute the five men, who include Binalshibh, a Yemeni, who allegedly found flight schools for the hijackers.
Waleed bin Attash, also from Yemen, stands accused of running an al-Qaeda training camp in Afghanistan and researching flight simulators. Mustafa Ahmad al-Hawsawi, a Saudi, allegedly helped the hijackers with money and credit cards, and Ali al-Aziz Ali, Mohammed's nephew and a Pakistani national, is alleged to have provided money to the terrorists.
"They can put them in prison for life. They can execute them," said Suzanne Sisolak, a New Yorker whose husband was killed in the Trade Center's North Tower. "They need to be stopped."
'Six months' is optimistic
Mohammed and his co-defendants are to be arraigned amid signs their lawyers are prepared for a drawn-out trial. Some of the defence teams said they would challenge the military tribunals and the secrecy shrouding the case.
The arraignment is "only the beginning of a trial that will take years to complete, followed by years of appellate review," said James Connell, who represents Ali. "I can't imagine any scenario where this thing gets wrapped up in six months."
The arraignment comes three years after President Barack Obama's failed effort to bring the men to the US for trial in a federal civilian court. Congress blocked the transfer of any prisoners from Guantanamo to the US, forcing the administration to refile the charges under a reformed military commission system.
Jim Harrington, a civilian attorney for Binalshibh, did not think any of the men would plead guilty, despite earlier statements that they were proud of the attacks and claimed responsibility.