Zacarias Moussaoui, one of the people convicted for relations with the 9/11 attacks, is said to have caused the death of over 3,000 people by keeping silent about the plot, according to prosecutors. Moussaoui, a loyal soldier from the al-Qaeda organization, knew of the plot but chose, while he was in jail, to lie to the federal agents questioning him.

The trial, which will last for 2 months, will decide whether the 37-year-old French citizen accused of being related to the attacks should be executed or spend the rest of his life in jail; he previously pleaded guilty, in April, for six counts, three of which carry the death penalty, including conspiring in acts of terrorism and hijacking planes with al-Qaeda.

Moussaoui was arrested a month before the September 2001 attacks, after raising suspicions at a flight school. The defense argued that the FBI knew more of the plans than Moussaoui did and still failed to stop the attacks.

Taking into account the incompetence of the FBI the defense speaks about, even if the accused told the truth, it would not have mattered. "Please don't make him a hero. He just doesn't deserve it," said Edward MacMahon, defence attorney, at the beginning of the trial.

Lead prosecutor Robert Spencer declared: "Even though he was in jail on September 11, 2001, Moussaoui did his part ... as a loyal al Qaeda soldier. His lies provided the operational security and allowed his brothers to go forward and kill. Had Moussaoui just told the truth on September 11, 2001, it would all have been different."

The accusations for which Zacarias Moussaoui is under trial are the conspiracy to commit acts of terrorism, aircraft piracy, aircraft destruction, use of weapons of mass destruction, murder and property destruction.