Cruel? That is debatable. Unusual? Hardly. It used to be extremely common. It is even called for in the Bible.<quoted text>
They have to be young and defenseless, but the death penalty for murderers in prison is cruel and unusual punishment.
Personally I am not in favor of it because if you execute the wrong person there is no taking it back. But if there was a way of being one hundred percent sure that a person did kill someone else, coldly and cruelly I would not be opposed to it at all.