You might check your statistics.    The states with highest execution rate also have the some of the highest murder rates.     Although the state is likely to kill an known murderer (as a some innocents(, it seems you also legitimize violence as way to show power.     It works for police, it works for gangs, it works for spouses.     Most people that commit henious crimes aren't particularly worried about capitical punishment and it certainly doesn't deter them.