Preponderance of evidence

This paper investigates the incentive properties of the standard of proof for a finding of negligence when evidence about injurers' behavior is imperfect. We show that a “more-likely-than-not” decision rule provides maximal incentives for potential tort-feasors to exert care. An injurer is then held liable whenever inadequate care appears more likely than due care, and not liable otherwise. Our analysis provides a deterrence rationale for the exclusionary rules of evidence found in common law and the preponderance of evidence standard of proof.