It is the same with murder. Depriving one of liberty who has taken a life, or many lives, does not register on the justice meter. If human life has the highest value (and that is debatable, given how it is treated), then the only way to validate its worth is to deprive one who takes it of his or her own life. That used to be known as the doctrine of "just desserts" before we entered into what C.S. Lewis called "The Humanitarian Theory of Punishment."
This trial should have been held in a military court, not a civilian one. Civilians are more likely to be stricken with a malady I call Oprah disease, which is all about feelings and little about objective truth. This malady affects every layer of public and private life. That a majority of jurors concluded that Moussaoui should not be executed because he had a difficult childhood was famously mocked by Stephen Sondheim's lyrics in the musical "West Side Story." One of the gang members says, "Hey, I'm depraved on account I'm deprived."
So, Moussaoui may have been right. He did win, in a sense, by again exposing America's soft moral underpinnings. Moussaoui deserved death. That he won't get it deprives him of justice. He will never have liberty again, but those whose deaths he plotted and rejoiced over will never have life again either. That isn't justice. It isn't even fair.