What criteria do doctors use to confirm someone is dead?

The 1981 Uniform Determination of Death Act (UDDA), accepted by the American Medical Association and the American Bar Association, defines death as sustaining "either;

(1) irreversible cessation of circulatory and respiratory functions, or

(2) irreversible cessation of all functions of the entire brain, including the brain stem..."

Although the UDDA has been adopted in all 50 states, each state uses it as a baseline only and may have stated exemptions to the definition.