I offer the Henry Lee McCollum case to point out that the death penalty is sometimes meted out when the crime is particular heinous, not when the certainty of guilt is particularly high.
"As regular readers may recall, Scalia specifically pointed to a convicted killer named Henry Lee McCollum as an obvious example of a man who deserved to be put to death."
MSNBC
"'For example, the case of an 11-year-old girl raped by four men and then killed by stuffing her panties down her throat,' Scalia wrote in Callins v. Collins. 'How enviable a quiet death by lethal injection compared with that!'
He was referring to Henry Lee McCollum, who at the time had already been on death row for 12 years. McCollum's conviction was overturned on Tuesday when DNA evidence implicated another man in the case. McCollum had been on death row for almost 30 years."
Huffpost For more on the McCollum/Brown Case see this
link.
Earlier I offered the James Earhart case. He was convicted primarily on the basis of a forensic technique (comparative bullet lead analysis) that was said to be probably not salvageable by the 2016 PCAST report. I am not certain that he was factually innocent or guilty, but I am certain about one thing.