I take it you meant "It's not only irrelevant", based on your prior post?
Perhaps Douglas thinks only murderers get the death penalty, in which case he can be forgiven for taking that view.
What has the bible got to do with a universal definition of morality? Are the courts a Christian institution?
What the jury sees as legal is, as I have pointed out in the very post you are replying to (and you are simply repeating the error), not necessarily the right thing to do. I know it's difficult to divine the correct course of action - that's my POINT.
The law exists to defend the rights that have been afforded by society to citizens. It is not a means of enforcing adherence to random religious beliefs, nor is it a means of exacting revenge.
Defence of the rights of individuals, or groups of individuals, should always seek to have the minimum necessary impact (i.e. - not excessive) on the rights of the defendent; otherwise the system is inherently hypocritical. That is why incarceration is preferable to the extreme measure that is execution.