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 Texas, the determination of death is governed by the Texas Health and Safety Code. The state follows the Uniform Determination of Death Act, which states that 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, according to ordinary standards of medical practice. The pronouncement of death must be made by a qualified physician. The use of artificial means of support may delay the pronouncement of death until the physician can determine that brain function has ceased irreversibly. It's important to note that while the pronouncement of death establishes that death has occurred, it does not establish the legal cause, manner, or exact time of death; these are determined separately, often through a death certificate or during a coroner or medical examiner's investigation.