More of @MorningStarling's arguments:
7. Civilised societies have been killing their citizens since the first civilised society developed. The ancient Athenians and Romans were civilised societies, so were the Aztecs, so to a large degree is the USA today - but all kept the death penalty
Neither the Athenians nor the Romans could be described as civilised societies. The fact that a supposedly civilised society currently is resorting, in some states, to using the death penalty is a massive weakness in any claim to be civilised.
8. Capital punishment is significantly cheaper than keeping someone in prison for decades. It's about 44K per prisoner per year. An execution could be done for a fraction of that, I think I could do it for under 2K per criminal including disposal of the body, less if they have family who want to reclaim it.
On that basis, again, let's not bother with keeping alive people with long term illnesses, the seriously disabled, etc etc. Indeed, why keep any prisoners alive? It would be so much cheaper to kill them. Saving money can never be a justification for deliberate state killing.
9. "Collateral damage" - what do you mean? The fact that innocent people could be wrongly executed? Guess what, people are wrongly convicted already, sometimes having decades of their life taken away from them. Execution is just a natural extension of this miscarriage of justice.
We can release people from prison, we can pay damages as compensation for wrongful conviction. It's not ideal, but it's a hell of a lot better than killing them. Would you feel this relaxed about it if it was you or someone you loved who had been wrongfully convicted and was going to be hanged tomorrow morning?
10. Execution achieves all aims of punishment - the forfeiture of the offender's life. That is the ultimate punishment. Execution might not allow for rehabilitation but rehabilitation is not supposed to be "punishment" - it's supposed to help the offender.
So does life imprisonment achieve all aims of punishment for appropriate offences.
11. On moral, ethical and above all financial grounds, capital punishment is a step that is well worth taking
Deliberate, cold-blooded killing is never either moral or ethical, and finances are irrelevant.