There are probably many categories: for example -
a) - obvious cases of severe injury and loss of so much blood that it causes cardiac arrest. Pretty easy to say that if the patient refuses blood in this situation, he has pretty much committed suicide for "religious" reasons.
b) - chronic illness which is likely to be fatal. Not taking blood might cause the person to die a little quicker, but they were going to die from the disease anyway.
c) - sometimes (ugly to say) blood transfusion is given during ordinary surgery in conditions where it could have been avoided. If a person refuses this, and for some reason complications set in, and they die - it would be difficult to say no blood caused it. Might well have happened anyway.
Anyway, like PSacremento says - we would look more reasonable (on a topic in which the JWs are vastly short of reason) if we just avoid making statements that cannot be reasonably proven.
That was my point.