@SPLEEN
You're dealing with quite a few misconceptions and those justifications are not "rubbish".
First, the reason the death penalty is more expensive than life in prison is due to mandatory appeals and prisoners fighting for their lives. Because of the legal rights granted to those prisoners, the cost of the lawyers, judges, investors in repeated long trials quickly becomes prohibitive. However, since we already know that we put innocent people to death despite the lengthy appeals process, scaling it back to make it more cost-effective is likely to lead to more innocent people being convicted.
As for "not deterring murder", no, it's not debatable. This is a subject that has been repeatedly studied and for you to call it a "number-juggling game" merely shows that you really don't have any background information on this. In fact, the reasons the death penalty doesn't deter murder turns out to be twofold: it's either a crime of passion or it's not. If the former (most murders are), it happens spontaneously before the guilty party thinks of the consequences. If it's the latter, the guilty party tends to plan and assume they won't get caught. Thus, no deterrent effect.
You also wrote:
"Are we supposed to believe that it's not OK to kill an innocent man but it is OK to put him in prison for life?"
That's a false dichotomy. No one is claiming it's OK to put an innocent man in prison. However, if they've been incorrectly convicted, you can't apologize to a dead man or give them *any* hope of regaining their life.
As for the death penalty, let's face it: it's not about protecting society (life in prison does this better since there's a lower cost to society) or about rehabilitating the prisoners (since they die). It's all about retribution and retribution is merely a pretty word for revenge. By supporting the death penalty, we're telling our children that revenge is an acceptable motivation for behavior. How enlightened :(
Biting the hand that feeds IT
