burden of proof
n. the requirement that the plaintiff (the party bringing a civil lawsuit) show by a "preponderance of evidence" or "weight of evidence" that all the facts necessary to win a judgment are presented and are probably true. In a criminal trial the burden of proof required of the prosecutor is to prove the guilt of the accused "beyond a reasonable doubt," a much more difficult task. Unless there is a complete failure to present substantial evidence of a vital fact (usually called an "element of the cause of action"), the ultimate decision as to whether the plaintiff has met his/her burden of proof rests with the jury or the judge if there is no jury. However, the burden of proof is not always on the plaintiff. In some issues it may shift to the defendant if he/she raises a factual issue in defense, such as a claim that he/she was not the registered owner of the car that hit the plaintiff, so the defendant has the burden to prove that defense. If at the close of the plaintiff's presentation he/she has not produced any evidence on a necessary fact (e.g. any evidence of damage) then the case may be dismissed without the defendant having to put on any evidence.