One day thru genetics or other means we will have better remedies for such rare offenses, maybe an injection or implant to modify behavior and bring the offending party to a better condition through a better understanding of human nature
If some creep came into your home, raped your wife and daughters, slit their throats and left with a grin on his face, would behavior modification satisfy your sense of justice? (Feel free to call it revenge.)
I have no problem with the death penalty.