DEFINITION OF HUMAN DEATH
It is important for social, legal, and religious purposes to determine what constitutes
death in humans. It is important for legal purposes to determine whether the death was natural (the result of illness) or whether a homicide was committed, as well as the order and timing of inheritance, whether life insurance should pay off, when health insurance should be discontinued, or when a country's leader ceases to be president. It is important for social and psychological purposes to determine when the grieving process should begin or when one becomes a widow or widower. It is important for religious purposes to determine when rituals should be performed.
Traditionally, the flowing of "vital" bodily fluidsÑblood and breathÑwas considered essential to human existence. These were measured by listening to the heart, feeling the pulse, and observing the breath flow. When they stopped
irreversibly, the individual was considered dead. With the development of organ transplantation, it became necessary to determine precisely which bodily functions were critical in declaring that the organism as a whole had died. Waiting to confirm that blood and breath had irreversibly ceased flowing could mean that it was too late to procure organs for transplant. More fundamentally, people began to question whether the essential characteristic of being alive was merely this fluid flow.
With the development of the ventilator, it was possible to maintain respiration, and therefore the beating of the heart and the flow of blood, even though the integration of bodily functions, which was under the control of the brain, was no longer possible. In 1968 a committee at Harvard Medical School proposed that
individuals be considered dead when their brain functions ceased irreversibly, even if they continued to breathe on a ventilator and their hearts continued to beat. According to the committee, this state could be determined medically by a series of neurological and clinical tests. Other groups have since proposed other tests. The view that individuals should be considered dead when all brain functions are destroyed had also been proposed by many philosophers and theologians. In 1970 the state of Kansas adopted this as a legal definition of death. Now all American jurisdictions have followed suit, as have most other countries around the world. The law now specifies that humans are dead when there is an irreversible cessation of all function of the entire brain. The only exception is New Jersey, which permits people to insist on the use of heart and lung criteria for death pronouncement if they specify this desire in advance.
This controversy is not completely resolved. The choice of which functions are essential is a value question and not one that can be resolved by medical science. Some cultural groups, including Japanese, native Americans, and Jews, continue to believe that humans should not be treated as dead until blood and breath irreversibly cease flowing. On the other hand, philosophers, theologians, and others increasingly question whether it is correct to insist that every function of the entire brain must cease before an individual as a whole can be considered dead. It is now clear that isolated nests of cells may remain alive in the brain because they continue to receive blood and that isolated nerve reflexes and hormonal functions can be maintained in what is otherwise a functionless brain. Some persons in a permanently unconscious state can breathe on their own because brain stem cells are alive, even though no other brain functions survive. These individuals are not legally dead by criteria based on whole-brain function. Some now advocate that such individuals should nevertheless be pronounced dead based on what is called a "higher-brain definition." This is not yet the law in any jurisdiction, however.