Traditionally death was declared only when the heart stopped beating. Today the patient can be declared dead by measuring brain stem functions. Brain stem is a part of the central nervous system, which if irreparably damaged, the patient stops breathing, other functions can no longer continue independently and the individual is dead. The heart may continue to function on ventilator and other support for a maximum up to 36-72 hours. This is the phase of brain death.

Brain death is declared by the brain death committee, which involves a team of four doctors who are not involved in the transplant team. This declaration is legal. This team has to perform the tests twice at a minimum gap of 6 hours so as to confirm the findings. This can only be done in institutions recognized for transplantations by the government. It is during this period that organs can be retrieved for transplantation after proper consent.