The BBC's Jonathan Beale describes the opening of the trial of the alleged mastermind of the 11 September 2001 attacks in the US and his four co-defendants in Guantanamo Bay.
Khalid Sheikh Mohammed said he would be representing himself
The US military calls it Camp Justice - a $12m (£6m) legal complex situated down the road from the detention camp that human rights activists describe as a modern-day Gulag.
The trial of the five so-called high-value detainees accused of plotting the 9/11 attacks was held at the now notorious Guantanamo Bay amid suffocating military security - the new courtroom was surrounded by razor wire fences.
This is an unusual setting for an unusual process in which the US military is the jailer, judge and jury of the five detainees being tried.
Khalid Sheikh Mohammed, the alleged mastermind of the attacks, was already sitting down when reporters were escorted into the building.
Beside him were his mostly uniformed legal team and a translator. Behind him - the alleged four co-conspirators, accused of aiding and taking part in the plot that killed almost 3,000 people.
'Enjoying the moment'
The focus of attention, though, was on the man often referred to by just his initials - KSM. He gesticulated and pointed to get the attention of his co-defendants.
The trials are taking place in Camp Justice, a complex set up on the base
We could not quite hear, but he was clearly passing on messages to the others facing trial.
One of the defending military lawyers complained that Sheikh Mohammed was intimidating his detainee - Mustafa Ahmad al-Hawsawi, a Saudi national.
The lawyer said KSM had mocked his defendant in Arabic by asking if Mr al-Hawsawi was in the American army for at first agreeing to be represented by a US soldier.
It reinforced the impression that Khalid Sheikh Mohammed was the leader. The US claims he was the third most senior figure in al-Qaeda.
His appearance has changed dramatically since the photograph taken on an early morning raid that led to his arrest in Rawalpindi, Pakistan, in 2003. Then he looked dishevelled and overweight. Now he was thinner and wearing a long grey beard, a robe and a prayer hat.
When he was addressed, he spoke in clear English, though it soon give way to a chant in Arabic in praise of Allah, which he occasionally interrupted to translate to the rest of the court.
It was clear that he was not intimidated by his surroundings or the charges against him - he was enjoying the moment.
He lectured the court that this was an inquisition, not a trial. He claimed that he had been tortured and then - much to the consternation of his legal team - he announced that he would be representing himself.
When the judge, a marine colonel, asked if he understood the significance of that decision - as he was facing the death penalty - Khalid Sheikh Mohammed made clear that he understood very well.
He said he had been looking to become a martyr for a very long time.
This is a taste of what is going to be an extraordinary trial.
The US military says that it has bent over backwards to make the proceedings transparent and fair.
But at times the judge ordered that the audio feed to those listening to be cut off.
It happened when Ramzi Binalshibh - a man who also said he wanted martyrdom - was asked about the medicine he had been taking. Even his own military lawyers had not been given those details.
At times, it was difficult to tell who was running the proceedings.
Ali Abd al-Aziz Ali - who is alleged to have helped finance the 9/11 hijackers - also denounced the trial in fluent English.
He said even though the government "tortured me free of charge for all these years, I can't accept lawyers under the circumstances".
He described the lawyers being offered to him as "decoys and decorations".
Human rights groups observing the proceedings predictably denounced them as a farce.
What is more surprising, is the condemnation coming from the men and women in American military uniform who have been given the task of defending the five men.
At a news conference at the end of a long day, one of them described the proceedings as "shameful".
What happened today, she said, tarnished the uniform. She added that it would not make the already difficult job of the judge any easier.