The last man executed in the UK was innocent, as were several before that. Suspicions over the validity of our hangins was part of the reason for abolition - we were quite quick on the drop and generally exoneration came only after the fact.
Then you have the hangman who tried (and failed) to kill him self.
The biggest problem with the death penalty, though, is that is "very murdered deserves death" you have to execute your executioners or the law is an Ass.
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