Death occurs when all vital functions of the body including heartbeat, brain activity (including the activity of the brain stem), and breathing stop irreversibly. Other signs of death include no pupil reaction to light, no jaw reflex (the jaw will contact involuntarily like the knee if tapped with a reflex hammer), no gag reflex (touching the back of the throat will induce vomiting), and no response to pain.

As medical technology improves, physicians, lawyers, religious leaders, and society as a whole must grapple with a changing definition of death. In the 1990s, the advancement in of organ transplant techniques, together with new technological tools to support life even when major organ systems fail, have made it necessary to develop more precise legal definitions of death and forced society to confront new philosophical ideas about death. Challenges for the future include deciding who should receive...