The concept of brain death evolved because advancements in medical science permitted unprecedented artificial maintenance of vital body functions by external means. Although the concept of brain death is accepted clinically, ethically, and legally in the United States, there is no national standard for the determination of brain death. There is evidence that variability and inconsistency in the process of determining brain death exist both in clinical settings and in State statutes. Several studies demonstrate that medical personnel determine brain death in variable ways, and have variable understandings of the definition of brain death. The declaration of death has significant legal consequences such as probate proceedings and liability issues for wrongful death. Inconsistencies in the determination of death may therefore be medically, ethically, and legally problematic.