Evidence Law and the Jury: A Reassessment

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McGill Law Journal


The common law of evidence is counterintuitive because it seeks to facilitate the search for truth by regulating fact- finders’ access to and evaluation of evidence. Since truth seems most likely to emerge when ad judicators reason freely from all available information, this puzzling strategy of seeking truth through evidentiary regulation demands some explanation. The orthodox explanation is that evidentiary regulation functions as a form of judicial control over the jury. Because juries are untrained, non-professional adjudicators, they are said to lack the competence to evaluate evidence. On this view, evidence rules are primarily directed at constraining jury decision making and preventing jury error. This jury-centred view has been criticized, and scholars have advanced other explanations for truth-seeking evidence rules. Some suggest that evidence law operates chiefly to promote the search for truth within the context of the adversary system , while others contend that evidence rules are primarily directed at managing the risk of witness dishonesty. This article examines the claim that evidence law represents a form of jury control, and also considers some competing explanations for evidence rules. The author argues that no single principle explains the law of evidence. A complex set of explanations is needed to account for the historical origins of the rules and to justify them analytically. Moreover, the salience of these various explanations can only be judged in particular doctrinal contexts. Jury-related rationales are most persuasive why ere there are solid reasons to believe that juries have trouble evaluating the particular form of evidence at issue. Social-scientific research does not support the conclusion that juries are generally incompetent adjudicators, but it does indicate that juries struggle with specific types of evidence. Consequently, the question whether a particular evidence rule can be justified on jury-control grounds depends, first, on the specific competencies required to evaluate the evidence and, second, on what is known about jury psychology and behaviour.