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 South Dakota, the determination of death is governed by state statutes that align with the medical and ethical standards commonly accepted across the United States. According to South Dakota Codified Law (SDCL) 34-12-1.1, an individual 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 law acknowledges that if artificial life support is in use, the determination of death must be made on the basis of brain function cessation. The pronouncement of death by a physician is a medical judgment regarding the cessation of life functions and does not itself establish the legal cause, manner, or exact time of death. These aspects are typically determined through a death investigation or autopsy when necessary.