This more than any other reason is why capital punishment is wrong. Even though this was for 2nd degree homicide that's irrelevant, errors in judgement convict many innocent people.

https://www.cbc.ca/newsinteractives/features/robert-mailman-walter-gillespie-new-brunswick-wrongful-conviction

The long wait for justice
In 1984, Robert Mailman and Walter Gillespie were convicted for second-degree murder in Saint John. Forty years later, a New Brunswick judge confirmed their innocence. What happened?