d246,
It wouldn't be negligence (on the driver's part) if they were forced to drive an unroadworthy vehicle.
There was no evidence of anything, because there was no cockpit voice recorder or accident data recorder fitted. Therefore, you cannot satisfy the required burden of proof. Possibility, probability and speculation (as acknowledged by Mr Wratten) all fall below that which is needed to find deceased pilots guilty of negligence.
I'm not grasping at straws either. Simply asking why the Reviewing Officers failed to stick to the rules in place at the time of the accident.
Kind regards,
Brian
"Justice has no expiry date" - John Cook