Objective Chance and the Rule against Character Evidence

Abstract

A central principle of U.S. law is that individuals should be judged in court based on their actions and not on their character. Rule 404 of the Federal Rules of Evidence therefore prohibits evidence of an individual’s previous acts to prove that the individual acted in accordance with a certain character or propensity. But courts regularly deviate from or altogether ignore this rule, resulting in arbitrary judgments based on an individual’s prior acts rather than on evidence regarding the events at issue in a case. This raises serious constitutional and fairness concerns, deepens racial and economic inequality in the criminal justice system, and creates a range of socially harmful incentives. I address this problem from a new angle—a scientific one. I argue that a type of evidence that I refer to as “objective-chance evidence” is at the center of the unpredictability surrounding the rule against character evidence. I apply a simple statistical model to resolve longstanding confusion regarding the nature of objective-chance evidence, and to demonstrate the need for a new approach to objective-chance evidence in the courts. I argue that central to a more logical and effective rule against character evidence is 1) a proper understanding of objective-chance evidence as a particular category of character evidence, and 2) an “objective-chance exception” that replaces the rule against character evidence with a 403-type balancing for objective-chance evidence. In turn, these steps permit a proper interpretation of Rule 404 and a stricter adherence to the rule against character evidence. Finally, I examine the feasibility of an objective-chance exception, and I demonstrate broad and significant implications for minimizing error in case outcomes and reducing inequality based on race and economic disadvantage in the criminal justice system. An earlier version of this article can be found at the following address: https://ssrn.com/abstract=3664837.