Common Law Evolution and judicial impact in the age of information

Abstract

All common law systems draw from the past. As judges draft opinions, they cite to relevant case law to guide their decision-making. These citations provide a record of how new legal developments draw on previous holdings. This Article presents the first thorough data-driven analysis of how different patterns of drawing from precedent are related to the influence a judicial opinion has on the evolution of the law. We show that there are previously undiscovered patterns in the way that common law systems evolve. By focusing on two measures of the age of the references cited in a judicial opinion—reach (average age of cited works) and range (variance of ages cited)—we find that there is one type of citation behavior that is strikingly more likely to be used in highly influential opinions. Cases featuring low reach and high range are more than twice as likely as other types of cases to go on to be highly influential opinions. Evidence for these conclusions are based on three sets of judicial opinions that span a century of time and diverse jurisdictions—the U.S. Supreme Court, the Supreme Court of Canada, and the Supreme Court of India. While these three jurisdictions vary in the way they cite to precedent, the single referencing pattern found to exist behind especially influential cases suggests there is a nearly universal commonality in the evolution of the law. Our findings help us better understand how common law high courts draw from the past to support important legal holdings. In addition to our substantive findings, this article demonstrates the power of computational legal studies of large datasets to generate novel analyses and findings of previously undiscovered empirical legal patterns.