The first stage of the trial of Khalid Sheikh Mohammed, accused of planning the 9/11 attacks, and four other suspects at a Guantanamo Bay military court got off to a rocky start when they refused to respond to questions.
The man who called himself the "mastermind" of the September 11 attacks, and his co-defendants - Walid bin Attash, Ramzi Bin alShibh, Ali Abdul Aziz Ali, Mustafa Ahmed Adam al Hawsawi appeared under heavy security today at the US base in Cuba.
The five men face charges that could lead to their execution.
The defendants engaged in what appeared to be a concerted silent protest against the proceedings.
Mohammed and his co-defendants took off the earphones that provide Arabic translations and refused to answer any questions from Judge Pohl, dramatically slowing a hearing that is heavy on military legal procedure.
ITV News' Nina Nannar reported that the start of the hearing was delayed after one of the defendants was restrained for refusing to come into the court.
Mohammed's civilian lawyer David Nevin said:
A closed-circuit TV feed of the court proceedings, which was also being relayed to seven viewing sites at military bases in the United States for journalists and family members of victims, was interrupted when the defence attorneys tried to discuss the way the defendants had been treated and used the word 'torture'.
However, Army Brigadier General Mark Martins, the chief prosecutor, said the commission provides many of the same protections that defendants would get in civilian court.
New rules adopted by the US Congress and Barack Obama has forbidden the use of testimony obtained through cruel treatment or torture.
Relatives of victims who died in the attacks of September 11, 2001 spoke ahead of the trials, six of which were chosen by a lottery to travel to Guantanamo to see the arraignment in person.
The five face charges that include terrorism and 2,976 counts of murder each for their alleged roles planning and aiding the September 11 attacks.