Has any one of the murders executed ever been pothumously proved innocent?
(*crickets chirping*)
The answer to your question is, “yes”, and many who were within hours of execution that were later proven innocent.
If you think prosecutors would not knowingly convict an accused they knew to be or were most likely innocent, you would be mistaken. Happens all the time. Even when a previously convicted person is declared actually innocent and exonerated by DNA evidence, the prosecutor most often insists the guy was guilty.