Well, before we go back and forth many many times, I'll write a conclusion.
As it stands right now, only a small fraction of those that have murdered, are executed. The problem is whether or not this small number is a deterrant against further murders.
Some people believe it is not, because some statistics show that murder rates actually rise in counties that support the Death Penalty.
Some people believe that the death penalty is a deterrant, it just isn't used enough to actually deter people. As it stands right now, only a small fraction of a percentage of murderers get executed.
However, it is not debatable whether or not the death penalty actually is a deterrant unless we start executing a very large percentage of Murderers.