There are two ways a doctor can declare a person legally dead.
The first is cardiopulmonary death.
It's when the heart stops beating and the lungs stop working.
After cardiopulmonary death, the body cells start to break down due to lack of oxygen.
This is the very beginning of the decomposition process.
Cardiopulmonary death has pretty much always been the best way to declare someone as absolutely dead, or what the medical establishment calls permanently and irrevocably dead.
But about 50 years ago, a group of Harvard doctors led by this guy came up with a second definition for death.
They said a person could be considered dead if the brain had ceased to function.
Brain death was different than a coma or vegetative state, where there are levels of consciousness and brain function.
Their reasoning was that the body couldn't function without the brain and a person without a functioning brain wasn't really a person anymore.
