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 Mississippi, the determination of death is guided by state statutes that align with the medical understanding of death. The state defines death as the irreversible cessation of a person's spontaneous respiratory and circulatory functions, or, in cases where artificial life support is involved, the irreversible cessation of all spontaneous brain function. This definition is consistent with the Uniform Determination of Death Act, which has been adopted in some form by most states. A physician, according to ordinary standards of medical practice, is responsible for making the pronouncement of death. It is important to note that while the pronouncement of death establishes that a person has died, it does not legally determine the cause, manner, or exact time of death. These aspects are typically determined through a death certificate or during a post-mortem examination if necessary.