I really don't know the answer to that question. It is the difficulty with this question that underlies my doubt about whether this was in fact unlawful homicide at all.
One needs to keep carefully in mind the distinction between what I will call obligation and what I will call duty. By the former, I mean moral obligation, in a good samaritan sense. By the latter, I mean a legal obligation.
In general, the law (at least in Australia, and perhaps subject to a qualification in the case of medical practitioners in certain circumstances, and perhaps for professional rescuers whilst engaged in their profession) does not impose any obligation to rescue another (ie the embark upon a rescue...once commenced, there may be some obligation to continue, and subject to recent statutory modifications some obligation to exercise due care in doing so). If I see someone drowning at the beach, and I do not make any effort to rescue them, even if it is within my capability to do so and could be done without danger to myself, I am not liable for standing there and doing nothing. Morally, I may be obliged to, but legally, I am not duty-bound to do so.
The question then arises, was there something about the relationship between Gabe and his wife (by which I mean, their relationship as buddies) that changes that position. I have some doubts that that relationship changes anything at all. Again, while there may be a moral obligation to assist, I doubt there is a legal obligation created. One of the reasons for that is that in practical terms, for many of us, we have little or no choice in who is our buddy, at least in some circumstances (I am think about going out on a boat on your own and being paired up with someone unknown by the DM, for example). And we certainly do not have the capacity to, for example, assess their capability beforehand. Importantly, for example, we have no ability to assess their ability to self-rescue, no capacity to assess the likelihood of uncontrolled panic, no knowledge of their level of fitness and other health-related aspects of diving. Those factors I think militate against the imposition of legal duty upon a buddy. On the other hand, of course, one of the things that the law of negligence cares deeply about is vulnerability, and one could argue that one's buddy is vulnerable in the sense that they will be looking to you to act in the event that they get into trouble. That, after all, is one of the primary purposes of diving in buddies I would have thought. I am not suggesting they have an expectation that you will be able to act competently so as to effect rescue, but at least act appropriately in trying to assist and if unable to do so to raise the alarm. However, in my view the law in Australia would likely come down on the side of obligation but no duty.
Assuming there is a duty, however, what then? It is then necessary to determine what the appropriate response in a given set of circumstances is. And one of the greatest difficulties here is that while the law tries to assess the reasonableness of your response objectively, one of the factors that will be relevant to that will be factors subjective to the putative rescuer. We are trained, even as rescue divers, not to attempt rescue unless it is reasonably safe to do so. That will involve a very personal judgment in each case, and depend upon subjective feelings of comfort and self-assessment of ability. This will change from diver to diver, and from time to time and place to place for any particular diver. The point I am trying to make is that it is very difficult to be able to say a priori what reasonable conduct requires of us, and that is usually a good indication that there is no legal duty to act. So while we might like to think the law would impose a duty on our buddy to try and help us, we might at the same time be reluctant to allow the law to look through the retrospectoscope and critically analyse our conduct as a rescuer.
I think it would be a sad day when the law imposed a legal obligation to rescue with consequences on the rescuer for failing to do so, or failing to do so adequately. There would be nothing more disasterous than a rescuer feeling pressured by legal obligation to attempt or continue an attempt at rescue, and thereby falling victim themselves (that is not to say that some would not feel such pressure from a moral obligation, but I would rather die trying to rescue someone because I thought it was the right thing to do, than because I was afraid that the victim might sue me, or worried that my liability insurance may not cover me etc).
Rest assured that this case has sufficiently troubled me to prompt me to do some more research on rescue, which I hope to turn into an article for our local sports law journal. So any insights or comments (polite ones of course) would be welcomed.
