Someone said the death penalty's not worth it because it doesn't work as a deterant. Nothing's a deterant for the creme of the criminal crop.
Capital punishment is in good company, on the scale of humaneness of punishment: emprisonment is just a less economical, more temporary solution to those criminals that will never live within lawfulness.
In the mean time lawful people will bear the economic burden of the inmates' upkeep... We've already had threads about this, and the righteous indignation of "more advanced countries" never fails to rear its head. As most people know, no country is irreproachable.. it's just a matter of choosing the right topics for any given country to earn an outright "more advanced" pedigree.
Not all of the USA is for the death penalty (so much for blanket statements!), and make no mistake, it is in the same intent for a healthier society as 'more advanced' nations tax lawful citizens to bear the cost of keeping criminals well-fed that the pro-capital punishment portion of Americans support the death penalty.
Now, the practical execution of the idea is another story..