John James: post-mortem toxicology is absolutely feasible and these days highly accurate providing the correct body is identified. For my sins I have attended a lot of fatal multi-casualty disasters in my career (the vast majority - but not all - thankfully non-aviation related) and I have little doubt that both the pre-mortem medical records and post-mortem toxicology will be respectively scrutinized and run very carefully. A post-mortem - and I hope this doesn't distress any relatives - will also be looking very carefully for medical problems such as tumours etc. which can absolutely cause aberrant behavior. But actually, the incidence of that is really low. It is not zero so most of the anecdotes people have read are true but it is low.