an interesting summary of the arguments against capital punishment from, of all places, the Foreign and Commonwealth Office website(!)
Common myths about the death penalty
"The death penalty is a deterrent"
This is not proven. Numerous studies have failed to establish that execution deters better than a long jail sentence. For example, the USA has the highest murder rate in the industrialised world, and rates are highest in Southern States where most executions occur.
"Murderers deserve no mercy"
All persons are entitled to full protection before the law and full observance of their human rights., including the right to a fair trial and the right to seek pardon or commutation of the sentence. Criminals must be brought to justice. But there are other means of doing this. And, with the death penalty, miscarriages of justice are irreversible.
The international community has agreed that even the worst offenders at the Rwandan and Yugoslav war crimes tribunals cannot face the death penalty. Criminals must be brought to justice. But there are other means of doing this.
"Most countries have the death penalty"
Not so. In 2002, 111 countries had ended capital punishment in law or practice. Only 84 retain it, and many of those have moratoriums*. The international consensus is now moving towards abolition.
"Most people want the death penalty"
Poll after poll finds that the more people know about the death penalty - and possible alternatives to execution - the more public support for the death penalty drops. That is why Britain works to encourage more debate about the death penalty in countries which retain it.