[Avodah] Brain Death

[David Riceman]

RHM, citing RYGB:

<<The issue is how to define the moment of death.>>

I want to quibble a little.  Hazal were not defining the moment of 
death; they were clarifying that lack of a heart beat establishes a 
hazakah of death.  As proof I'll point out that no one permits murdering 
people who have had heart transplants.

But hazakot are not exclusive, and are facts of nature or sociology, not 
decrees of Hazal.  So the question about brain death is whether it 
establishes a hazakah.  I don't know enough about medicine to even 
approach the question, but I'll add a couple of questions anyway.

We can't actually observe cessation of brain activity, we can only 
define "brain death" using complex machinery.  Are there any examples in 
Hazal of hazakot which can be established only through machinery?

I noticed that wikipedia defines brain death as "irreversible cessation 
...."  Is it possible to measure irreversibility, or do you need a 
second hazakah for that? Are there other examples of serially coupled 
hazakot?

Incidentally, to support RYGB's main point, see chapter 6 of Sa'adyah's 
commentary on Sefer Yetzirah (R. Kafih's edition; the one printed in the 
standard edition is a different book, apparently by someone else).

David Riceman