Of note:
A mental-health professional was quoted this morning on one of the U.S. news channels as saying "My obligations and responsibilities regarding patient confidentiality just came to an end on a French mountainside."
Expect the laws to change regarding PC - especially for professions that hold such a great responsibility for the lives of others.
Regarding the presence of CC or a relief pilot in the cockpit to cover the temporary absence of one pilot:
By law (at least in many jurisdictions) seated pilots are required to be strapped into their seats during flight. And may be required to have their O2 masks on when alone at the controls (in case of a rapid decompression event).
Exactly how is a pilot so restrained, and in the cramped confines of the cockpit, going to attack or disable the second person in the cockpit so rapidly that (s)he cannot call for help, or unlock the cockpit door for assistance to enter?
The mere presence of another human, with eyes and a brain and a moral conscience (as opposed to a passive video system) changes the psychological dynamics in the cabin, compared to being alone. There are some things it is simply much harder to do - psychologically - when someone else is present and observing you.
Think not? Why did this co-pilot wait until he was alone to take this action? Egypt Air shows that he could have - with some probability - brought the aircraft down even with the PIC trying to stop him in a full fist-fight.
But doing it alone - in "secret" and hidden from the eyes and judgements of others - made it easier.
@NigelOnDraft - the "Commander" of an aircraft is the person with 4 stripes on his/her shoulders. Regardless of whether that pilot is PF or PM, in the left seat, or in the loo, or taking a kip in the crew rest area.
If the rules say a second person shall take his position (certainly not his place as a pilot) when absent, it is implicit that that person is also "deputized" - to monitor the remaining pilot, not for flight actions as such, but for possible physical or mental impairment. As well as simply being a pair of hands to open the d**n door when needed.
On the continuing allusions to the FO possibly having suffered hypoxia - how did this happen to him alone? The pilot was functional enough to knock and bang on the door.
On the "premature" release of evidence and some conclusions from the investigation:
Once you have reasonable suspicion of a criminal act ("probable cause"), time is of the essence. You have to start looking for additional clues RIGHT NOW, before they get destroyed. The FO's discarded down-check notice was in the trash - and might well have been lost except for prompt action by authorities.