A Primary Activity Approach to Proof Burdens

The question of which party should bear the burden of proof on a given factual issue remains one of the most important and problematic in evidence and procedure. This paper approaches the question from a relatively unstudied perspective, viewing litigation as a device for influencing primary activity behavior rather than as a standalone search for truth. Its main finding is as follows: when a given evidentiary contest concerns the primary activity behavior of one of the parties, placing the burden of proof on the other party maximizes the incentive impact of that contest. Though counterintuitive, the finding accords with a striking regularity in existing law. The adversary of the incentive target typically does bear the burden of proof with regard to the target's primary activity behavior. Thus, in tort, the plaintiff bears the burden on the defendant's negligence, but the defendant typically bears the burden on the defense that the plaintiff was contributorily negligent. And in contract the plaintiff bears the burden on the defendant's nonperformance, while the defendant bears the burden of proof on his defense that the plaintiff failed to perform