Are racial stereotypes a proper basis for legal fact-finding? What about gender stereotypes, sincerely believed by the factfinder and informed by the fact-finder's life experience? What about population averages: if people of a certain gender, education level, and past criminal history exhibit a statistically greater incidence of violent behavior than the population overall, is this evidence that a given person within this class did act violently on a particular occasion? The intuitive answer is that none of these feel like proper bases on which fact-finders should be deciding cases. But why not? Nothing in traditional probability or belief-based theories of fact-finding justifies excluding any of these inferences. Maybe intuition goes astray here. Or maybe something about the traditional theory of fact-finding is wrong. Arguing the latter, this article proposes a new theory of factfinding. In contrast to historic probability and belief-based theories, this paper suggests that idealized fact-finding is an application of likelihood reasoning-the statistical analog of

the ancient legal concept of the "weight of evidence" and the formal analog of modern descriptions of legal fact-finding as a process of comparing the relative plausibility of competing factual stories on the evidence.

This likelihood theory marks a fundamental change in our understanding of fact-finding, with equally fundamental implications for practice and procedure. The theory simplifies fact-finding, describing every burden of persuasion as an application of the same reasoning principle. It harmonizes recent scholarship on fact-finding, showing that work on the cognitive processes of fact-finders can be formalized in a comprehensive and coherent theory of the ideal fact-finding process. It explains evidentiary mores, justifying hostility to naked statistical evidence, for example. And it provides new insights into the effects of subjective beliefs on fact-finding, showing not only the harm that results from asking factfinders to decide cases based on their personal beliefs about the facts, but also the way forward in reorienting factfinding away from prejudice, bias, and subjective beliefs, and toward the firmer ground of the evidence itself.

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