The condition of having a sound and rational mind; being mentally healthy and having the ability to distinguish right from wrong. In all jurisdictions, being sane is presumed, and it is up to the defense to prove the contrary to be true. Synonymous with sanity. See also insanity and insanity defense. sanity hearing. 1 An examination of one's mental competency to see whether one is mentally equipped to stand trial. 2 A court proceeding, held to determine whether a person's mental health dictat...