in my opinion there have been 4 pilots and all of them had lots of hours. Basic flying skills had to be there. Not checking speed and altitude and not to answer both are dropping is a huge failure of all of them. Even if one of the pilots, lets say the pilot flying (PF), did not recognize it, what's about the other gentlemen? Why didn't they respond?
In some ways I think this crash is unique because
(1) We have a hull loss with fatalities.
(2) So far as we can guess right now, some degree of pilot error was involved. Perhaps gross error, or even negligence. Perhaps.
(3) Flight crew is alive
(4) Lots of forensics data: CVR, video, United crew that witnessed, relief pilots etc.
Asides of the NTSB investigation (which so far as I know does not assign blame) what's the chance of a criminal prosecution being filed? ( Almost certainly, civil suits will result. ) What's the dividing line between an accident and culpable negligence?
Historically, what precedents do we have for scheduled carrier flight crew being prosecuted for an incident? Do they enjoy any immunities? Have there been any successful prosecutions?