As four men sat in prison for a murder they didn't commit, records show that state investigators sent proof of their innocence to a North Carolina prosecutor but he never revealed it to the convicted men.

That's not unusual: Just 13 states have a rule requiring prosecutors to come forward if they find "new, credible and material evidence" that an innocent person is serving time. The State Bar in North Carolina is reconsidering the rule, which it rejected in 2009.

The four men and a fifth one who also pleaded guilty in the case received a total of $8 million from the Buncombe County for their wrongful imprisonment.

The American Bar Association wrote the post-conviction rule and recommends it. Each state decides whether to accept it.