A second attempt to prosecute Khalid Sheikh Mohammed, who claims to have "masterminded" the September 11 2001 terrorist attacks on New York, and his alleged accomplices kicked off yesterday with a 13-hour hearing.
The case is being heard by a military tribunal in the Guantanamo Bay concentration camp after the US Congress scuppered the Obama administration's attempts to bring the five defendants to the US for civilian trial.
The government claims that new rules imposed on the tribunal forbidding testimony obtained through "torture or cruel treatment" means that the proceedings will be as fair as if they were heard in an ordinary court.
But human rights groups and defence lawyers for the five say that the secrecy that prevails at Guantanamo make it impossible for the suspects to get a fair trial.
Rights activists also accuse the government of keeping the case away from the civilian courts deliberately to avoid highlighting how the defendants had been treated in custody - with Mr Mohammed having been waterboarded 183 times during his incarceration.
The five, who face 2,976 counts of murder and terrorism for the attacks on the World Trade Centre and could face the death penalty if convicted, refused to participate in the hearing, remaining silent when asked whether they would accept the lawyers provided for them and removing their headphones so they could not hear the Arabic translations of the proceedings.
Ramzi Binalshibh, who is accused of assisting in arranging the flights, began praying during the middle of questioning before saying that he believed a prison official was planning to kill him and claim it was suicide.