An Aggregation Theory of Character Evidence
Journal of Legal Studies (Forthcoming)
28 Pages Posted: 9 Jul 2021 Last revised: 17 Sep 2021
Date Written: July 19, 2020
Courts frequently depart from Federal Rule of Evidence 404, which prohibits evidence of a person’s prior acts to prove that the person acted according to a certain character or propensity. This leads to verdicts that are unpredictable and based on behavior not at issue in a case. I develop a theory of “aggregation evidence,” which draws on principles of estimation and data aggregation in statistics and ties together evidence from a broad range of contexts. I apply this theory to analyze the effects of character evidence on accuracy, and to understand why and when courts depart from the rule against character evidence. I show that a type of character evidence that I call “objective-chance evidence” stands apart from other forms of character evidence in its ability to improve accuracy. I then argue that a formal exception for this type of evidence may hold the key to a more coherent rule.
An earlier version of this article can be found at the following address on the author page at: https://ssrn.com/abstract=3664837.
Keywords: character evidence, Rule 404, Federal Rules of Evidence, FRE, doctrine of chances, prior-acts evidence, other-acts evidence, propensity evidence, doctrine of objective chances, judgment variability, unpredictability, accuracy, bias-variance tradeoff, shrinkage estimation, hierarchical model
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