Virginia ? The jury weighing Zacarias Moussaoui’s role in the deaths on Sept. 11, 2001, asked for a definition of “weapons of mass destruction” Thursday as it worked to decide whether the al-Qaida conspirator is eligible for the death penalty.

The jurors obtained the definition as deliberations neared four hours. U.S. District Judge Leonie Brinkema told them the term includes airplanes used as missiles. One of the three convictions on which Moussaoui could receive the death penalty is conspiracy to use weapons of mass destruction.

The jury went home Thursday afternoon, having deliberated more than seven hours over two days.

Meanwhile, federal prosecutors in Philadelphia are investigating a government lawyer, Carla J. Martin, who nearly derailed Moussaoui’s sentencing trial by what Brinkema ruled was improper coaching of witnesses and lying to defense attorneys.