Introduction
"When is a patient dead?" is a hotly debated, emotional subject. Although declaring death involves well-thought-out criteria and test guidelines, some doctors feel that those criteria are self-serving or immoral. The determination of death -- and the way death criteria are applied -- can vary by physician and setting. A patient declared dead or brain dead in one setting might be considered alive in another.[1]

Leslie Kane, MA
One thing is certain: Determining death is a huge and wrenching responsibility that doctors take very seriously.
Unless you insist that death means that every last detectable spark of life is gone, one way or another we make some sort of compromise with how we define death that falls short of complete, utter, total death. The question is, why do we need compromises? Why not wait until every last cell in the patient is dead? Is it for practical reasons? Is it for societal reasons, because if you waited until the last spark of life was snuffed out, there would be fewer organ transplants?
Death criteria affect several vital areas. First, there is the potential for organ donation: Because brain death is considered legal death, surgeons can harvest organs and save other lives. The criteria also affect resuscitation: When a patient's heart has stopped, how long do you keep resuscitation attempts going before you decide that his or her state is irreversible?