Kent asks why capital defense costs more than it needs to. His answer is apt to the Loughner case in which the question arises, but let me suggest a broader answer.
Capital defense costs more than it needs to because we indulge its excesses. When we stop indulging them, they'll disappear.
Case in point: Timothy McVeigh. McVeigh's defense cost $13,780,835.83. And it wasn't even a real defense. It was a story woven about some third character who was said to have been involved. Even assuming the story were true, which it was not, it would not have constituted a defense or even mitigation. If Mr. X were also involved, that would not dilute McVeigh's actions or his culpability for them. And this would be true even if McVeigh had not gone on "Sixty Minutes" to calmly explain, not merely that he had done it, but why he had done it (as part of an undeclared war on the USA).
It's beyond absurd that the taxpayers should have had to pay nearly fourteen million dollars for the non-defense of a man who bragged about his guilt. Maybe we thought we could afford absurdities at the time, but we know now that we can't.
To coin a phrase, we need to cut and cap. States should cap defense expenditures in capital cases at $1,000,000. The idea that we cannot fairly determine factual guilt and blame for that amount of money is ridiculous. If, in some wildly exceptional case, the court were to determine that it was impossilbe to provide a constitutionally adequate defense for that amount, the court could add up to another $250,000. But that's it. The days of spending without limit are over.
We don't need to end the death penalty. We need to end the limitless indulgence we have given those who seek to bleed us dry to evade it.