The most persuasive argument for me against capital punishment is the risk of the state executing a person quite innocent of the charges laid against her/him.

Surely too ghastly to contemplate, even if that means we all have to live with greater risk of being murdered: we have to hope for the best without the deterrent effect of the death penalty, plus knowing that a murderer may serve out a sentence and emerge from prison to kill again.

In effect, to save one innocent life we accept that other innocents are likely to – and do – die.

How to calculate that risk?

Not that many people are murdered, so compared to lots of other risks it is pretty small for most people, although in some inner city areas in the UK it must be notably higher.

But for other purposes (eg the evil Precautionary Principle) the argument is turned on its head. Nothing must be accepted (eg a new drug) which puts even one life at risk! Are you saying that the life of a human being can be costed? How heartless are you? 

Here is one policy area where the British state kills about 1000 innocent people each year, with the aim of avoiding the birth of Down Syndrome babies. Yet in this massacre roughly 10% of the babies killed actually do not have Downs at all.

So does anyone know why it is morally wrong for the state to execute the most vile and vicious proven murderers, but morally OK for the state to kill so many healthy and innocent babies for health-care policy reasons?

Just asking.