Photo of Sean P. Sullivan

I'm a law professor at the University of Iowa.

My research interests include

  • Evidence Law
  • Antitrust Law
  • Law and Economics

I do interdisciplinary research—combining methodologies from law, economics, and statistics to find new ways to approach traditional legal issues. I am particularly interested in using game theory, probability, and controlled experiments to revitalize procedural and doctrinal dialog in areas where standard legal research methods have stalled.

Evidence Law

My primary interest in evidence law is using probability theory and theoretical statistics to unpack and reinterpret difficult evidence problems. For example, one of my forthcoming publications, A Likelihood Story, tackles a century-old evidence-law puzzle: how to conceptualize the fact-finding process. This paper shows that mounting frustration with decades efforts to devise a probability-based theory of fact-finding owes to a mistaken focus on probabilities: we should really be looking at likelihoods. These are fundamentally different concepts. A probability approach to fact-finding asks about the personal beliefs after seeing the evidence; a likelihood approach asks what the evidence alone shows. I argue that the same simple and intuitive rule of likelihood reasoning describes every burden of persuasion in use today.

Antitrust Law

My interest in antitrust issues stems from the growing role that economics plays in this area of law. But its role could be bigger still. For example, in What Structural Presumption?, I show how a seemingly innocuous bit of legal formalism has subtly displaced necessary economic analysis in an important area of merger law. In a similar vein, I am interested in re-examining the old and potentially outdated legal factors thought to represent necessary conditions for competing firms to engage in anticompetitive coordination. I am also interested in finding cross-subject applications for antitrust and business-law principles. In a forthcoming publication, Powers, But How Much Power?, I use concepts from both antitrust (collusion) and agency law (principal-agent interaction) to reinterpret and partially defend Supreme Court doctrine on the constitutionality of delegations of legislative powers.

Law and Economics

Finally, I am interested in a variety subjects that might be classified as traditional law-and-economics topics. Much of this work involves the individual decision-making problems that arise from, and comprise, the civil justice system. For example, in Why Wait to Settle?, I conduct a rare empirical test of the popular theory that delays in the settlement of lawsuits could be the result of informational asymmetries between litigants. Using data from an economic experiment in which subjects engage in mock lawsuits for real money, I find that the introduction of informational asymmetries increases settlement delay by as much as 90%. In addition to my experimental work on legal negotiation, I am also coauthor of the experimental economics chapter of the Oxford Handbook of Law and Economics.