We analyze the design of legal principles and procedures for court decision-making in civil litigation. The objective is the provision of appropriate incentives for potential tort-feasors to exert care, when evidence about care is imperfect and may be distorted by the parties. Efficiency is shown to be consistent with courts adjudicating on the basis of the preponderance of evidence standard of proof together with common law exclusionary rules. Inefficient equilibria may nevertheless also arise under these rules. Directing courts as to the assignment of the burden of proof is then useful as a coordination device. Alternatively, burden of proof guidelines are unnecessary if courts are allowed a more active or inquisitorial role, by contrast with that of passive adjudicator.