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In 1968, the Ad Hoc Committee at Harvard Medical School defined death as an irreversible coma (brain death) and specified the criteria. Nowadays, its conclusions remain the main reference on a global level.

A few years after the work of the Ad Hoc Committee, neuropathological studies showed that in brain death, the linchpin was the damage to the brain stem. Whether it is due to an injury to the skull, anoxia or a haemorrhage, a major lesion in the brain leads to a high level of intracranial pressure, which crushes the brain stem and destroys it. This part is especially responsible for controlling the respiratory system.

In the traditional theoretical approach, whose roots are American, the neurological criteria of death relate to the “whole brain”, as the Anglo-Saxons say. However, basing themselves on neuropathological studies, Great Britain, then India, moved away from this vision of the problem (brain death) and adopted criteria focusing on the brain stem alone. “In practice, that doesn’t change much because, even according to the conception that brings the whole brain into play, clinical tests relate to the reflexes of the brain stem”, explains Steven Laureys.

Initiated in 1971 by a Scottish neurologist, J.B. Brierley, a third minor trend spread to the United States, then Europe. Adopted by philosophers and lawyers, it is based on the concept of “neocortical death”: human beings are characterised by their consciousness and their social interactions; consequently, if the extent of the brain lesions prevent any conscious relations with the external world, they must be considered dead. “This life is not a life”, the supporters of this trend believe, who include patients in a vegetative state and anencephalitic children among the number of dead, thus justifying the right to remove their organs for transplantations.

This conception of death has been a hot topic in the ethical debate. In particular, there was the case of Terri Schiavo, which moved the whole of American society and was on the front pages of the world’s newspapers. “The vegetative state cannot be assimilated with brain death”, Steven Laureys specifies. “Recovery cannot be excluded in certain cases, during the first few months.”

Today still, the definition of death on the basis of the criteria of brain death is contested by doctors, philosophers and ultraconservative Catholic theologians. For them, the only acceptable criteria is an irreversible halt to blood circulation.