People die in many ways, but in medicine there are only two reasons a person can be declared dead: Either the heart has stopped or the brain has ceased to function, even if the heart is still beating. A person may serve as an organ donor only after being declared dead. (Until then, transplant surgeons are not allowed even to interact with a dying patient.) This common-sensical rule underpins organ donation in the United States and many other countries. Most donor organs today are obtained after brain death, defined by most state laws as a condition of permanent unconsciousness...