RESUMEN
It is not infrequent for physicians or lawyers who only occasionally deal with medical expert opinions to have difficulty understanding terms used in a legal context. A question of proof relating to consequences of an accidental injury can refer to the accidental injury itself and it seems relatively unknown that the term accident can apply to both the event and the damage/harm to health. The special situations with mental injuries (psychotrauma) are not dealt with in this article.This article explains the concepts and terms that are frequently used in relation to questions of causality and explains the fundamentals of medical causality assessment, from the viewpoint of both medical expertise and law. The focus is on private and public accident insurance, but the law relating to accidents at work of public officials and liability are also considered.