Credibility by Proxy

Abstract

Evidence jurisprudence assumes that impeachment rules are intended to help determine the truth of the matter by identifying liars. For example, a witness’s credibility can be impeached with evidence that she has a fraud conviction because in theory that conviction suggests she is deceitful and is therefore likely to lie under oath. Scholars, judges and rulemakers have criticized this system of impeachment, demonstrating again and again that the rules are ineffective at identifying liars and lack any social science basis. Yet the impeachment rules endure. This Article identifies the reason for their endurance in the face of overwhelming evidence: impeachment rules are not and never have been about identifying false statements in order to get to the truth. The purpose of these rules is to identify which persons have the culturally recognized moral integrity or honor to be worthy of belief in court. In other words, impeachment rules enforce not a scientific but a status-based view of truth in which status markers, such as reputation and prior crimes, determine who will be deemed a probable liar. I show this using both historical and modern examples. The effect of this categorical error (confusing status with veracity) is to abandon the avowed purpose of evidence law – truth seeking – in favor of the very different, and potentially contrary goal of norm enforcement. The side-effect is that it perpetuates systemic biases in the justice system. It may be that soon we will have some scientific way to identify liars. In the interim, though, we should abandon status as a proxy for credibility.