Abstract

A central assumption of modern evidence law is that its rules are rules of admissibility only. That is, they tell judges whether or not a given piece of evidence may be viewed by the fact-finder, but they do not purport to tell the finder of fact how to evaluate the evidence once admitted. One can imagine, however, a system of rules that help fact-finders weigh evidence by instructing them, for instance, that the law considers a class of evidence (say, hearsay) to be of "low weight." In fact, such rules - rules of weight - are an old idea with roots in Roman Law. But they have long been ignored by evidence scholars or, when considered, judged to be anachronistic and deeply inconsistent with a system of trial by jury. This Article argues that such hostility to rules of weight is unjustified and that their use should be taken seriously as a possible direction for evidence reform. Given that jury trials are now increasingly rare and that, when a jury is used, its discretion is already constrained in a number of ways, the orthodox view of rules of weight now itself seems outdated. Furthermore, there are reasons to think that such rules could be beneficial for forensic fact-finding. The past use of them by courts, their current role in administrative adjudication, and recent research in cognitive psychology all suggest ways in which rules of weight could make fact-finding fairer, more efficient, and, most important, more accurate. Such benefits make the Supreme Court's recent condemnation of the use of rules of weight in the administrative context that much more difficult to justify.