Scientific Models of Legal Reasoning

Economics, Artificial Intelligence, and the Physical Sciences

Scott Brewer

• Publisher: Routledge
• Year: 2013
• eBook ISBN:
  9781136524837
• Topic: Philosophy
• Subtopic: Philosophy History & Theory

First published in 1998. This five-volume series contains some of this century's most influential or thought provoking articles on the subject of legal argument that have appeared in Anglo-American philosophy journals and law reviews. This volume offers a collection of essays by philosophers and legal scholars on economics, artificial intelligence and the physical sciences.

LEGAL PRECEDENT: A THEORETICAL AND EMPIRICAL ANALYSIS^*

WILLIAM M. LANDES and RICHARD A. POSNER

University of Chicago Law School and
National Bureau of Economic Research

I. INTRODUCTION

IN a legal system such as ours, in which legislative bodies confine themselves for the most part to prescribing general norms of conduct rather than highly specific rules, the published decisions of courts and administrative agencies interpreting and applying the legislative enactments are important sources of the specific rules of law. When the parties to a legal dispute are unable to agree on the meaning of the governing statute as applied to their dispute, litigation may ensue in which that meaning will be an issue for the court to resolve. The court's resolution will define the specific requirements of the statute in the circumstances presented by the case and thus create (subject to a qualification noted below) a specific rule of legal obligation applicable to like circumstances.

The rules produced by the process of adjudication are distinctive in being implicit rather than explicit rules.¹ The rule promulgated by a decision is not the court's express statement, if any, of a rule; rather, it is the court's holding that is, the minimum rule (whether or not expressly articulated) necessary to explain the outcome of the case. The rule created by a single decision will therefore tend to be extremely narrow in scope; a broader rule will generally require a series of judicial decisions—a string of holdings—for it is only from a series of decisions, each determining the legal significance of a slightly different set of facts, that a rule applicable to a situation common or general enough to be likely to recur in the future can be inferred.

A factor pushing in the same direction is that the authority of a rule declared in a single decision is limited unless the rule is declared by a higher court for the guidance of a lower one in the same jurisdiction. Especially in appellate litigation, most of the judge-made rules urged on the court are those of a coequal court, or those declared in the earlier decisions of the same court; such rules have persuasive force, but are not binding. Where, however, the rule has been, as it were, solidified in a long line of decisions, the authority of the rule is enhanced. The rule then represents the accumulated experience of many judges responding to the arguments and evidence of many lawyers and is therefore more likely to be followed in subsequent cases.

The distinctive attributes of decisional rules are captured in the term that the legal system uses to describe such rules: “precedents.” In ordinary language, a precedent is something done in the past that is appealed to as a reason for doing the same thing again. It is much the same in law. The earlier decision provides a reason for deciding a subsequent similar case the same way, and a series of related precedents may crystallize a rule having almost the same force as a statutory rule. Accordingly, legal precedents are more accurately described as inputs into the production of judge-made rules of law than as the rules themselves; but this refinement will be ignored in this paper to simplify the exposition.

The use of precedents to create rules of legal obligation has, to our knowledge, received little theoretical or empirical analysis.² This paper presents and tests empirically an economic approach to legal precedent that is derived mainly from the analysis of capital formation and investment. We treat the body of legal precedents created by judicial decisions in prior periods as a capital stock that yields a flow of information services which depreciates over time as new conditions arise that were not foreseen by the framers of the existing precedents. New (and replacement) capital is created by investment in the production of precedents.

The basic data for the empirical analysis are case citations appearing in judicial opinions. An initial problem is that a case citation is not the same thing as a precedent. Sometimes a case is not cited as a precedent; an example is a citation of the decision of a lower court (or courts) in the same case. Our samples exclude this obvious nonprecedential citation and other, less obvious, ones.³ In some instances, counting citations may result in underestimating the true number of precedents by excluding the precedent that is so effective in defining the requirements of the law that it prevents legal disputes from arising in the first place or, if they do arise, induces them to be settled without litigation. In the limit, such a “superprecedent” might never be cited in an appellate opinion yet have greater precedential significance than the most frequently cited cases. But such cases are probably rare. If a case is highly specific, it will hardly qualify as a “superprecedent”; by definition it will control only those infrequent cases that present virtually identical facts to those of the case in which it was originally announced. If it is highly general, and therefore more likely to be an important precedent, it is unlikely to decide—so clearly as to prevent disputes or litigation from arising—the specific form of the question presented in subsequent cases.

Citations by scientists and other scholars to scientific and scholarly books and articles (rather than by lawyers and judges to cases) have been studied extensively by historians of science, by sociologists, and by economists.⁴ Scholarly citations, however, are not examples of the use of precedent. The normal function of the scholarly citation is not to adduce authority for a proposition but to give credit for prior original work, to refer the reader to corroborative or collateral findings by other scholars, and as a method of incorporating by reference relevant theorems, proofs, etc. Since the second and third functions of scholarly citation have counterparts in judicial citation, studies of scholarly citation may have relevance to understanding judicial citation, but the present paper does not explore the possible parallels between scholarly and judicial citation.

The idea of analyzing judicial citation practices for regularities that might refute or support hypotheses derived from capital theory will no doubt strike some lawyers, both practicing and academic, as a dubious undertaking. Not only are many lawyer...

Table of contents

• Front Cover
• Half Title
• Title Page
• Copyright
• Contents
• Introduction
• Law and Scientific Method
• Rules Versus Standards: An Economic Analysis
• Legal Precedent: A Theoretical and Empirical Analysis
• Reflections on Taxman: An Experiment in Artificial Intelligence and Legal Reasoning
• The Decline of Law as an Autonomous Discipline: 1962–1987
• Artificial Intelligence and Law: Stepping Stones to a Model of Legal Reasoning
• Arguments and Cases: An Inevitable Intertwining
• A Theory of Preliminary Fact Investigation
• The Curvature of Constitutional Space: What Lawyers Can Learn from Modern Physics
• Acknowledgments