In my humble opinion I suggest that when it comes to this topic there will never be agreement amongst all and each side will pile stats and emotional pleas on till the cows come home. I have looked at the stats and some seem accurate, and some seem questionable.
However I have found one stat on this subject that is simply indisputable and I believe makes the case
There has NEVER been a repeat offender amongst those put to death. For whatever reason they simply do not commit any further crimes or re-offend once the sentence is carried out. So while the death penalty may or may not act as a deterrent to the general public it has been proven to be a 100% effective deterrent to those that have been subject to it.
So based on this unshakable fact it is hard to understand an opposing view from someone whose argument relies on every second or third word or phrase being "maybe" , "what if", "could happen", "its possible", or the best of them all "you never know.
However if anyone can prove the stat I quoted earlier is wrong and that an individual in fact re-offended after having a death sentence carried out I am certainly willing to re-evaluate my stand on this subject.