Folks,
this is an important thread on an important issue, which thankfully occurs very rarely. A few points.
1. Dealing with an incapacitated flight crew member is something that should be in every airline's SOPs. I am rather taken aback by the lack of a single contribution which starts "our airline's SOPs are to do ...." There are a bunch of decisions to be made; about when, how and where, and by whom, to try resuscitation, which are not trivial and should not have to be made on the fly. And these SOPs should be regularly reviewed.
2. Many of the contributors to this thread have obviously not had to deal with medical emergencies and their main corollary, dead people, on a regular basis. The question: what do I do if my crew dies on me? is valid and requires an answer a little more grounded than expressing condolences and sending a card.
3. Ancient Geek has done nothing more than relate an experience and make a triage suggestion. In doing so, he has contributed more in terms of points 1 and 2 above than any of those contributors who criticise him for it (and, in contrast to those who berate him for his contribution, he has been neither impolite nor inappropriate).
I didn't know whether he is right or wrong about iris response as an appropriate way of deciding whether resuscitation is worthwhile. So I asked my partner, who is a dialysis nurse; they quasi-regularly have such emergencies.
She says check pulse, breathing, maybe eyes (iris contraction), but that there is no single indication that someone is dead. Lack of iris contraction indicates brain damage of some sort, but one cannot thereby conclude that the victim is dead. She says that resuscitation must always be tried. But of course she operates in a relatively unconstrained situation.
They perfom CPR, on a special board, because almost everything else is too flexible to perform it properly. The defibrillators may only be used by a doctor (they don't have a "layperson's defibrillator"). I asked what one would do if it happened to a captain in-flight. It is obviously not possible to perform CPR on someone in a seat, but she doesn't know if one could effectively apply a lay defibrillator on a sitting person.
There are other people I could ask; for example, an acquaintance who is a full-time emergency-response doctor. But I think this is enough for now. This commentary just goes to support point 1 above.
It looks as if iris-response is just one of a constellation of things to try, none of which, either alone or all together, forms a universally valid decision criterion for death.
4. Concerning the trope that only a registered medical doctor may determine death in England and Wales and the US and other countries, prima facie it rather misses the interesting point, which is: what do you do if it happens in your presence? It is a question which most people who put themselves out of quick access to medical services (for example, most people who go sailing, backpacking, trecking, rock-climbing, mountaineering, cross-country skiing, even hunting and angling) are wise to ask themselves, and indeed such guidance is available.
However, there is a point here for aircrew. Crew may be wise first to ask whether there is a doctor on board and solicit hisher help without delay. If there is, and heshe is willing, then heshe can perform the relevant determinations and guide response. (There may be the problem of persuading a doctor to undertake the responsibility.) If not, then the legal issue is irrelevant and the crew must do what they think best. The very best is that they follow established guidance in their SOPs, because if they improvise, and someone disagrees later with what was done, they might have a liability problem which they would not necessarily have (although their airline might have) if it's in SOPs.
5. There is obviously a tension between the necessity to revive someone suffering from cardiac arrest, and the risk to flight involved in removing them to a place in which this may be attempted. This risk should be mitigated through a proper risk analysis and determination of appropriate procedures to mitigate risk, and we are back to point 1 above.
PBL