“the state’s first posthumous pardon - a document that finally proves his innocence.”
Though this is commonly believed, it’s completely wrong. Burdick v. United States shows that a pardon carries an ‘imputation of guilt’, and accepting a pardon is ‘an admission of guilt’.
Since the guy’s dead, he can neither accept nor reject the pardon. He also cannot appeal to have his sentence overturned, which is what we should do if he were still kicking.
Hopefully the pardon contained language stating he was innocent of the charges, not just “pardoned.”