Ah, the justice system:

Mr. Moussaoui’s lawyers urged him not to plead guilty, but they could not tell him why.

"Incredibly," the brief said, "defense counsel had evidence specifically found to be material and exculpatory as to Moussaoui, but at the time of the plea his lawyers could not discuss that evidence or even tell Moussaoui it existed. No plea can be knowing and counseled under these circumstances."