Definition reprinted with permission from Committee on Psychiatry and Law, of the Group for the Advancement of Psychiatry: Mental Health Professional and the Legal System
The degree of probability to which factual assertions must be proven to allow a moving party to prevail in litigation. For example, the state must prove a criminal defendant's guilt "beyond a reasonable doubt" in order to obtain a conviction. A person's mental illness and harmfulness must be shown by "clear and convincing evidence" before involuntary hospitalization is legal. A plaintiff must demonstrate malpractice by a "preponderance of the evidence" in order to win damages in a personal injury action. (see also burden of proof).