We are talking about being judged in a criminal case in a Court of Law - I don't see how an Ombudman would fit into that situation.
AFAIK Ombudsman are never employed in criminal cases.
As for the idea of specialist jurors who have a detailed knowledge of the merits of the case in hand, this idea has been mooted for complex fraud cases - mainly by the prosecution who find it very difficult to secure convictions in that type of case - I don't think the original poster who started this thread had the idea that not enough flight crew were being prosecuted!
