According to the study published in Proceedings of the National Academy of Sciences it was determined that at least 4% of people who were on death row have been innocent and not guilty of any charges they were on death row for.
So that means that around 4% of people who were executed were likely innocent and should've never been executed.
Actually nobody should be executed even though they've murdered someone or people because all the law and prison system is doing is just murdering someone for murdering someone.
So that means that it's not illegal for the justice system and law to murder someone but they can punish someone for murdering someone or people.
That is not right and I believe it would be more torture just to let the prisoner stay in prison for a long time until they die from natural causes.