Sounds interesting. The idea is that he would plead guilty to the charges so the court would proceed directly to a death penalty phase. That is, what is usually the second phase of a capital case would in fact be the whole trial: a jury would be chosen and a trial would take place, but the only issue at the trial would be whether Moussaoui should be executed — he would already stand convicted. Presumably, if he “won” the trial (i.e., if the jury did not vote in favor of imposing the death penalty), he would get a sentence of life imprisonment.