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 Delaware, the determination of death is governed by state statutes that align with the medical and ethical standards commonly accepted. According to Delaware law, a person is legally declared dead when there is an irreversible cessation of all spontaneous brain functions, known as brain death, or when there is an irreversible cessation of spontaneous respiratory and circulatory functions. The use of artificial life support may complicate the determination of death, but if a physician, adhering to accepted medical standards, concludes that there is irreversible cessation of brain function, the individual can be pronounced dead. The formal pronouncement of death by a physician does not, however, establish the legal cause, manner, or exact time of death; it merely establishes that death has occurred. The legal determination of these aspects may require further investigation or certification by a coroner or medical examiner.