Just read of George Pickering of Texas who was in coma. Doctors said he was brain dead and there was no hope. They wanted to take him off life support. His mother agreed. But father did not and took a gun to prevent the doctors from removing it. After a long standoff with police, it turned out George suddenly showed signs of life. He totally recovered. The doctors were wrong. Nevertheless the father was sent to jail. Nothing was done to the doctors.
Did the doctors really say he was brain dead? Or did they actually say he was comatose, vegetative, or in one of the other minimally conscious but alive states, and the news media reported it as "brain dead" for dramatic effect?
There is a world of difference between "dead" and any state that afflicts the living. A dead brain no more jumps back to life than the dead steak you are about to have for dinner.
And, for the record, I am glad that the father of George Pickering did not take the diagnosis of "irreversible" coma to heart and allow life support to be discontinued. Coma patients have been known to wake up even after years. It seems that the brain does have some regenerative capability.