IMO, there are 3 crimes which duly-merit the death penalty: murder (not killing), rape and child molestation. Animal torture & abuse merits a blowtorch/pliers, for 2hrs.
The problem, in the case of rape and child molestation, is you run the risk of perpetrators just killing their victims. If the penalty is death anyway, why not just kill and dispose of the body so they can't talk.
Capital punishment for murder I agree with. For the other two, life without parole seems more sensible to me.