The determination and pronouncement of when a person has died has medical, ethical, and legal implications. Laws vary from state to state, and death is usually defined in a state’s statutes.

Definitions and terminology may vary from state to state but generally a person is dead when, according to ordinary standards of medical practice, there is irreversible cessation of the person's spontaneous respiratory and circulatory functions. If artificial means of support preclude a determination that a person's spontaneous respiratory and circulatory functions have ceased, the person is dead when, in the announced opinion of a physician, according to ordinary standards of medical practice, there is irreversible cessation of all spontaneous brain function.

Death occurs when the relevant functions cease. But a formal pronouncement of death is not a legal determination of the cause, manner, or time of death.

In Arizona, the determination of death is governed by state statutes which align with the medical and ethical standards commonly accepted. According to Arizona Revised Statutes § 36-849, a person is legally declared dead if there is an irreversible cessation of circulatory and respiratory functions, or if there is an irreversible cessation of all functions of the entire brain, including the brain stem, as determined by a licensed physician. The use of artificial life support may necessitate the latter criteria to be applied. The pronouncement of death by a physician is a medical determination that a person has died, which is distinct from a legal determination of the cause, manner, or time of death. This legal determination is typically made by a coroner or medical examiner through a death investigation.