According to the Presidential Council on Bioethics, a group of individuals appointed by President George W. Bush to advise his administration on ethical issues related to advances in science biomedical and technology, the need for criteria to define death became important after the invention of the mechanical ventilator, an artificial support for patients who cannot breathe independently due to injury or infirmity (The Presidential Council 2). The definition of death was very simple before the development of ventilators; patients died when the heart stopped beating (post 1946). However, it became possible for circulatory and respiratory function to continue without neurological function with the help of cardiac support devices (Truog and Robinson 2391). Many ethical and philosophical questions arose when many hospitals around the world began using ventilators. Furthermore, it became difficult for doctors to decide the time of death for patients who had irreversible brain functions and were kept under machines. Should a human being with complete brain failure be considered dead? When ...