IFPS man Isn't the suicide suggestion conjecture? Was it not possible that the F/O was starting to have some massive medical event just before the captain left the flight deck and which subsequently developed into him becoming unconscious. iF any post mortem examination is possible, could that be determined?
Answer to your PM question and toxicology is simply yes but only if you have enough tissue available to analyse. Depends upon how much blood is still present in tissues and the exposure to air/temp etc. There is a time limit to this if you are questioning things like carbon mono oxide etc. Hypoxia can not be determine in these cases unless a fully body ( or very large chunks of it) can be found.
(sorry if some of you find it too gory, please feel free to delete it if Mods thing that it is too gory for non medics)