Sudden Onset Rule Law and Legal Definition

Sudden-onset rule refers to a legal principle stating that a medical testimony is unnecessary to prove causation of obvious symptoms of an injury. Under the sudden-onset rule, causation may be inferred by a lay jury, without the aid of medical testimony. [Tucker v. Wibbenmeyer, 901 S.W.2d 350 (Mo. Ct. App. 1995)]. This rule applies when obvious symptoms of an injury follows a trauma immediately, or with only short delay. The most obvious cases are where a person involved in an accident suffers a broken bone or open wound.