It is so easy to call such mistakes "criminal". I believe these verdicts do nothing but establish public executions for vengeance, and they do nothing to further the safety that we all seek.
It would be interesting if the public lawyers who prosecute these cases were held to the same standard. What if prosecutors were held to the same standard? If they make legal mistakes, and fail to convict true criminals (after all, their mistake endangers the public!) shouldn't prosecutors be sent to jail?
My point is, when does a mistake become a crime? I do believe in civil liability for one's actions, I do not believe in criminal penalties when professionals act in reasonable good faith.