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 Pennsylvania, the determination of death is governed by the state's statutes, which align with the general medical and legal standards for defining death. According to Pennsylvania law, a person is considered legally dead when there is an irreversible cessation of circulatory and respiratory functions, or when there is an irreversible cessation of all functions of the entire brain, including the brain stem, as determined by a physician. The use of artificial means of support does not alter the determination of death if these criteria are met. The pronouncement of death is a medical determination that must be made according to ordinary standards of medical practice. It is important to note that while the pronouncement of death establishes that death has occurred, it does not legally establish the cause, manner, or exact time of death. These aspects may be determined through further medical examination or investigation, such as an autopsy or a coroner's inquest.