[M 91 u2 K]

And killing murderers is self defense also.

Since 1971 10,000 people have been killed by people who were convicted on murder and released.

And the Death Penalty is used to punish and deter prisoners from killing guards.

[wmichgrad]

Since 1971 10,000 people have been killed by people who were convicted on murder and released

Life without parole would solve that problem.

And the Death Penalty is used to punish and deter prisoners from killing guards

If it's not a deterrent to keep people from killing a person in the first place, then I doubt that is what keeps them from killing guards. I would think the pain and suffering that would be inflicted by other guards should they kill one is more of a deterrent.