This Article identifies a discrepancy between law and epistemology and proposes a way to fix it. Our legal system relies on decisions of multimember tribunals, which include juries, state and federal appellate courts, and supreme courts. Members of those tribunals often disagree with each other on matters of fact. The system settles such disagreement by applying head-counting rules: the unanimity or supermajority requirement for jury verdicts and the majority rule for judges ' decisions. Under these rules, jurors can return an agreed-upon verdict even when their reasons for supporting the verdict are inconsistent with one another. Similarly, judges are authorized to deliver any decision so long as it is supported by a majority of the panel. Disagreements among judges and jurors are consequently ironed out instead of being accounted for as a factor that reduces the reliability of the final decision.
By adopting these rules, our legal system allows jurors to convict the defendant when six of them believe the incriminating account provided by one witness, while rejecting as non-credible the testimony of another prosecution witness, and the remaining six jurors form a diametrically opposite view of the two witnesses' credibility. Moreover, the system authorizes appellate courts to determine by a narrow 2-1 majority that a violation of the accused's constitutional trial right was "harmless beyond a reasonable doubt." Likewise, it accords the status of an unreservedly binding precedent to a 5-4 decision of the United States Supreme Court that determines the meaning of a statutory or constitutional provision.
These rules are fundamentally incompatible with the epistemological principles of rational fact-finding. The epistemology of disagreement maintains that when a person makes a factual finding and then realizes that an equally informed, competent, and honest individual--an "epistemic peer"--arrived at a different conclusion, based on the same information, she ought to scale down her level of confidence in her own opinion. A peer's disagreement is evidence writ large that a person cannot rationally ignore or discount. Rather, it must be given weight and cause one to revisit her original opinion.
This epistemological principle has far-reaching implications for the law. For example, a guilty verdict rendered by a jury cannot be considered unanimous when the underlying reasons contradict each other; a dissent by a single appellate judge should preclude a guilty sentence under the "beyond a reasonable doubt " standard; and a precedent laid down by a narrow majority of the Supreme Court should remain open to reconsideration.
INTRODUCTION I. THE EPISTEMOLOGY OF DISAGREEMENT A. Disagreement as Evidence B. Implications for Law and Legal Theory II. DISAGREEMENTS WITHIN THE JURY A. Theory B. Doctrine 1. The "Bottom Line" Rule 2. The "Hung Jury" Rule III. DISAGREEMENTS IN THE COURTS OF APPEALS A. Theory B. Doctrine IV. DISAGREEMENTS ABOUT MEANINGS OF STATUTES AND CONSTITUTION A. Theory 1. Analytical Background 2. Epistemology at Work 3. Illustrations B. Doctrine CONCLUSION INTRODUCTION
Judges, jurors, and other decision-makers who make factual findings, identify applicable laws, ascertain the meanings of those laws, and determine their implications for individual cases are the lifeblood of our legal system. These decision-makers, however, often disagree with each other. The disagreements span across facts of individual cases and the meanings of statutes, common law doctrines, and the constitution. To address disagreements, the legal system has developed different decision rules for multimember tribunals, which include the unanimity or near-unanimity requirement for jury verdicts and the majority vote for appellate courts' and the Supreme Court's decisions. (1)
Scholars have examined those rules from an economic, political, and psychological perspective. (2) Conspicuously absent from this list is the epistemology of disagreement--a rapidly developing discipline that analyzes the effects of a disagreement on the truth-value of the underlying decision. (3)
This discipline focuses on two big questions. First and most importantly, should a person revise and possibly modify her decision after learning that an "epistemic peer"--a decision-maker with roughly similar information and decisional capabilities--disagrees with it? Relatedly, does the fact that an equally informed and competent decision-maker disagrees with the person's decision reduce the decision's reliability? (4)
As I explain in this Article, both of these questions should be answered affirmatively. (5) When a person's decision encompasses factual findings, the fact that her epistemic peer disagrees with her makes the decision less reliable than the decision-maker originally thought. Any such disagreement is evidence writ large, which the person cannot justifiably ignore, concerning the accuracy of the decision. From an epistemological perspective, a decision-maker must revise her confidence in the decision in a way that takes account of her peer's disagreement.
The revision process can proceed along one of three different paths. First and most straightforwardly, a decision-maker may decide to modify her initial decision. Alternatively, she may acknowledge that her decision is not as reliable as she originally thought. Finally, she may choose to disavow her factual claims and recast her decision into a subjective opinion, intuition, or value preference. From an epistemological standpoint, if the person digs her heels in the ground and makes neither of these decisional adjustments, her decision would be unjustified, if not altogether irrational. (6)
To illustrate this pivotal insight, consider a case featuring two young associates in a law firm, Anna and Bill, who go out to lunch together and agree to split the check. When the check arrives, Anna and Bill glance at the check and continue their conversation. Ten minutes later, they discover that the check disappeared from the table. Asking the waiter to bring a new check is against social etiquette. Anna calculates that she and Bill must pay for the meal $26 each. She tells Bill about it, but Bill informs her that according to his calculation, each must pay $30. Can Anna justifiably refuse to modify her decision? (7)
Epistemologists widely believe that Anna cannot justifiably refuse to do so. (8) Bill and she have the same information about the cost of the meal. Presumptively, Bill's memory and capacity to make simple algebraic calculations is not inferior to Anna's. Bill's disagreement with Anna consequently constitutes evidence that requires Anna to revise and modify her statement. Perhaps Anna should tell Bill that, since he and she were equally likely to miscalculate the requisite payment, each of them should leave $28 on the table. (9) At a minimum, Anna ought to acknowledge that her decision is not as reliable and creditworthy as she initially thought it was. (10)
The fact that a person's epistemic peer disagrees with her is best conceptualized as second-order evidence. (11) Second-order evidence is a broad category: it includes any information pertaining to the reliability and implications of the primary (first-order) evidence that supports the person's factual findings. From this perspective, Bill's disagreement with Anna constitutes second-order evidence that affects the reliability of Anna's factual finding. This disagreement indicates that Anna may have miscalculated the payment, or, alternatively, missed something when she looked at the check. Hence, if Anna is interested in making an epistemically justified decision, she ought to account for these possibilities and update her initial finding accordingly. Not doing so would be a mistake. If Anna could justifiably ignore Bill's calculation, then Bill, too, could justifiably do the same and stand steadfastly behind his original evaluation. Consequently, both Bill's and Anna's decisions would be deemed creditworthy and reliable, which is patently absurd.
This epistemological insight has profound implications for the law. Specifically, it can help policymakers improve the rules governing non-unanimous decisions of multimember tribunals: the jury, courts of appeals, state supreme courts, and the United States Supreme Court. These tribunals consist of epistemic peers (12): judges and jurors who exercise equal participatory powers in the tribunal's decision after weighing the same evidence and same information about relevant legal issues. At the end of the proceeding, these epistemic peers consult with each other, deliberate and vote. They do not always vote the same way, and for that reason their disagreements must be properly accounted for in the final decision. Unfortunately, rules that presently resolve such disagreements do not achieve this result. (13)
Consider a bank robbery case in which twelve jurors unanimously conclude that the defendant perpetrated the alleged crime. Of the twelve, six base their conclusion on the testimony of a passerby who identified the defendant as a robber, while rejecting as untrustworthy a similar testimony of the bank's cashier. The remaining six form the opposite view: they believe the cashier and assign no credibility to the passerby. From an epistemological point of view, the dissent coming from each group of jurors reduces the reliability of the other jurors' decision. This second-order evidence undercuts the credibility that jurors assign to each witness to a degree that arguably should preclude the jury from convicting the defendant.
Assume now that ten jurors out of twelve unreservedly believe the passerby, while the remaining two jurors do not consider any of the witnesses credible. From an epistemological standpoint, the prosecution's case now becomes stronger than before. Although the defendant can still rely on the two jurors' dissent as second-order evidence, this dissent has weak epistemic...