The use of statistical techniques to tease out empirical patterns in legal contexts has had a profound impact on legal practice and scholarship over the past few decades. From employment discrimination claims to academic studies of judicial voting patterns, we have learned a lot from regression analyses and other statistical applications. But getting at the deep structure of law has been more difficult with that tool kit. The convergence of big data, network theory, data visualization, and vastly enhanced computational capacities is changing that–now we can begin studying law and legal systems in ways that open up new frontiers for practitioners and academics.
As a practical example, sign on to Ravel Law. You will find a simple search field with no instructions. Plug in a term–I used “climate change.” Whereas in Westlaw and Lexis you receive a list of cases, in Ravel Law you receive something very different. Ravel Law gives you the list of cases, to be sure, but it also displays an interactive graphic representation of the citation network of all cases using the search term. The visual representation allows the user effortlessly and instantly to identify cases citing cases, the strength of each case as a citation source for others, and the timeline of cases in the network. So, if a practitioner wants to identify the “big case” in a topic, or to quickly trace the growth of the topic in case law, Ravel Law finds it for you in seconds, whereas piecing that together through traditional searches would take hours and a lot of mental gymnastics.
On a more theoretical level, tools like those used to power Ravel Law can help academics plumb the deeper structure of legal systems. For example, legal concepts and principles can be broken down into finely grained components, as in the way legal research services such as Westlaw and Lexis have developed their “keynote” and “headnote” cataloging systems. These cataloging systems produce hierarchical concept frameworks placing broad legal concepts such as constitutional law and environmental law at the top and then drill down from those broad concepts through successive levels of increasingly narrow subtopics. Michael Bommarito’s study of opinion headnotes in over 23,000 Supreme Court cases illustrates the branching form of what this hierarchy looks like when laid out graphically. (See Michael J. Bommarito II, Exploring Relationships Between Legal Concepts in the United States Supreme Court). As any lawyer knows, however, cases often are about more than one narrow sub-sub-subtopic. Rather, a particular judicial opinion could involve a combination of numerous broad and narrow concepts from various parts of this hierarchical framework. As Bommarito’s study vividly demonstrates, when mapped over masses of opinions and long time frames these combinations exhibit patterns of concept relationships that are not inherently obvious from an examination of the multitude of discrete components of the concept hierarchy. So, how do these patterns form–how do the multitude of discrete legal concepts get thrown together in thousands of cases over time in ways that exhibit strong conceptual interconnections? The answer lies in the work of the multitude of interconnected institutional agents in the legal system–the lawyers and judges–working within the system’s structure to litigate and decide cases. Factual contexts, litigation strategies, and judicial reasoning combine to bring together a web of legal concepts particular to each case, but as Bommarito’s study shows, over time we find the concept hierarchy as a whole to exhibit various strong and weak concept interconnections. These revealed interconnection patterns are not explicitly built into or otherwise obvious from the concept hierarchy itself, the purpose of which, quite to the contrary, is about disaggregating legal concepts into finely grained discrete concepts; rather, they are macro-scale emergent behavior of the legal system.
Ravel Law and Bommarito’s headnote study are just the tip of the iceberg in what will soon become possible for practitioners and academics through network analytic and other new empirical tools. Welcome to the next generation of empirical legal studies!