Let me re-phrase... If I'm brain dead and there is zero chance of me feeling pain, they can take my organs. I just want them to be sure I'm brain dead. How i

Let me re-phrase... If I'm brain dead and there is zero chance of me feeling pain, they can take my organs. I just want them to be sure I'm brain dead. How is that determined? (oh and my brain is not an electrical cpu, I understand your analogy but I'm not sure it applies given the complexity of a human brain, for example certain parts of a brain can be "off" while the others are "on")