The *only* reason for capital punishment is retribution, which is based in nothing other than hatred, which is a vile and unhealthy emotion. Nobody--not even "monsters"--deserves to be tortured or killed. Whatever way someone is, there are reasons they are that way, and if you were in their shoes in every conceivable respect then you'd do the same thing they did. Inasmuch as anyone "deserves" anything, everybody deserves whatever's best for them and everyone else involved. For the human race to be truly successful, we have to move beyond judging and condemning each other and start embracing and understanding each other--even the "worst" of us, who are just humanity itself put in an unpalatable light.