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. Last Updated: 07/27/2016

Trial Begins for Sept. 11 Conspirator

ALEXANDRIA, Virginia -- Zacarias Moussaoui may be the defendant, but it's the FBI that was likely to be on trial once testimony began Monday in the confessed al-Qaida conspirator's death penalty trial.

Both prosecutors and defense lawyers have indicated that FBI agents will provide key testimony at Moussaoui's sentencing trial, which will determine whether the 37-year-old Frenchman is sentenced to life in prison or death. Moussaoui's trial has been more than four years in the making. He is the only person in the United States who has been charged in connection with the attacks that took place on Sept. 11, 2001.

He has already pleaded guilty to conspiring with al-Qaida to hijack planes and commit other crimes. The trial will simply determine Moussaoui's punishment, and only two options are available: death or life in prison.

To obtain the death penalty, prosecutors must first prove a direct link between Moussaoui and the Sept. 11 attacks. Moussaoui denies any connection to them and says he was training for a possible future attack.

The actions and abilities of FBI and other federal agents will be key issues at the trial, given the hefty legal burden prosecutors carry in the case. Prosecutors will try to link Moussaoui to Sept. 11 by arguing that the FBI would have prevented the attacks if only Moussaoui had told the truth to the FBI about his terrorist links when he was arrested in August 2001.