Brain death is used as an indicator of legal death in many jurisdictions, but the definition varies.
Why Is Brain Death Important?
This issue is critically important to deceased organ donation.
Medical technology has advanced to the point where mechanical ventilation can provide oxygen to the lungs of a person who has ceased breathing on their own. And the heart may actually keep beating temporarily if it continues to receive oxygen, even after brain death. If oxygenated blood continues to flow, organs can remain viable, suitable for transplant, and may be used to save lives.
Unfortunately, the body begins to deteriorate rapidly once breathing and heartbeat stop. After a short period of time, organs such as the heart, liver and kidneys are no longer suitable for transplant.
For people who believe that brain death does not qualify as halachic death, the possibility of deceased organ donation is greatly restricted.
Brain Death in the United States
The United States currently uses the Neurological Standard, or whole brain death.
In 1981 the President’s Commission for the Study of Ethical Problems in Medicine and Biomedical and Behavioral Research studied this issue. The Commission accepted the neurological standard as one of two valid standards for determining death. (The other is the traditional cardiopulmonary standard.) But, the issue was not settled after this report.
In 2008, the President’s Council on Bioethics issued a 150 page white paper titled “Controversies in the Determination of Death.” Their main conclusion was to reconfirm the neurological standard as valid. However, they did discuss some remaining controversies in detail.
Brain Death in Israel
Brain death is legally accepted as halachic death, according to Israel’s Chief Rabbinate.
The Brain-Respiratory Death Law, 5768 – 2008, sets out strict standards under which organ donation and transplantation can take place. (See Requirements of the Brain-Respiratory Death Law.)
However, even with these standards in place, some rabbinic authorities disagree and do not approve of this law. (See Remaining Controversies page)
For more on this subject, see Wikipedia or the Halachic Organ Donor Society – Medical FAQS.