The verdict was received with silence in the packed courtroom, where one row was lined with victims' families.

In their successful defense of Moussaoui, defense lawyers overcame the impact of two dramatic appearances by Moussaoui himself ¡ª first to renounce his four years of denying any involvement in the attacks and then to gloat over the pain of those who lost loved ones.

Using evidence gathered in the largest investigation in U.S. history, prosecutors achieved a preliminary victory last month when the jury ruled Moussaoui's lies to federal agents a month before the attacks made him eligible for the death penalty because they kept agents from discovering some of the hijackers.

But even with heart-rending testimony from nearly four dozen victims and their relatives ¡ª testimony that forced some jurors to wipe tears from their eyes ¡ª the jury was not convinced that Moussaoui, who was in jail on Sept. 11, deserved to die.

The case broke new ground in the understanding of Sept. 11, releasing to the public the first transcript and playing in court the cockpit tape of United Flight 93's last half hour. The tape captured the sounds of terrorists hijacking the aircraft over Pennsylvania and passengers trying to retake the jet until it crashed in a field.