Brain death is the complete and irreversible loss of brain function, including involuntary functions needed to sustain life. It is determined by the Uniform Determination of Death Act and is different from a persistent vegetative state where the person is still alive. Medical technologies have made it possible to sustain lives of those with severe brain injuries, but has the law kept up? At what point is someone with a severe brain injury or persistent vegetative state legally dead? Those with zero brain activity are considered legally dead.