Christians and the death penalty

Here is a brief but interesting article about serial killers and why Christians should never be advocates for the death penalty. Simply put, someone who is alive still has the opportunity for redemption, so we as Christians should never eliminate that possibility for another human being. As far as we know, death is the end of all opportunities for redemption. (Although I'm not totally certain about that...but in any case I'm sure Christ would love to see us all live to accept him.) As a pacifist I can't help but think that this should apply to all killing, including warfare.