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 Ohio, the determination of death is governed by the Ohio Revised Code (ORC) 2108.30, which aligns with the Uniform Determination of Death Act. According to this statute, an individual is legally dead if they have sustained either an irreversible cessation of circulatory and respiratory functions, or an irreversible cessation of all functions of the entire brain, including the brain stem. This determination must be made in accordance with accepted medical standards. The pronouncement of death is typically made by a licensed physician, and while it establishes that death has occurred, it does not itself determine the legal cause, manner, or exact time of death. These aspects are often determined through a death certificate, autopsy, or inquest, depending on the circumstances surrounding the death.