> For example a braindead person is "undisputedly" dead
No, they’re not. If they were indisputably dead we’d just say dead. The qualifier means it’s something other than actually dead.
You could quibble that after medical death biological processes continue in various cells and organs for a while though. And of course there’s the old first responder’s adage that the patient isn’t dead until he’s warm and dead. Cold and dead, as in fished out of ice water, isn’t necessary dead dead.
This is a good example of a premise that isn’t generally acceptable. If we agree that persons who lack agency have no right to not be killed then we can kill infants, the severely mentally ill, involuntarily commited persons, and arguably severely physically disabled persons.
Not to mention, determining who does and doesn’t have agency and thus a right to not be killed strikes me as considerably trickier than the basic medical definition of dead, which is basically no heartbeat. Hence the observation that cold and dead might not really be dead. Severe hypothermia can make the pulse undetectable.
> basic medical definition of dead, which is basically no heartbeat
This is an extremely reductive statement. There is no unified medical definition of death, precisely because it's a highly controversial topic.
Closest to what you're trying to say is UDDA (which, ironically, is currently being revised), and it explicitly mentions brain death: "An individual who has sustained either (1) irreversible cessation of circulatory and respiratory functions, or (2) irreversible cessation of all functions of the entire brain, including the brain stem, is dead."
No, they’re not. If they were indisputably dead we’d just say dead. The qualifier means it’s something other than actually dead.
You could quibble that after medical death biological processes continue in various cells and organs for a while though. And of course there’s the old first responder’s adage that the patient isn’t dead until he’s warm and dead. Cold and dead, as in fished out of ice water, isn’t necessary dead dead.