Partisan Panel Composition and Reliance on Earlier Opinions in the Circuit Courts

Does the partisan composition of three-judge panels affect how earlier opinions are treated and thus how the law develops? Using a novel data set of Shepard's treatments for all cases decided in the U.S. courts of appeals from 1974 to 2017, we investigate three different versions of this question. First, are panels composed of three Democratic (Republican) appointees more likely to follow opinions decided by panels of three Democratic (Republican) appointees than are panels composed of three Republican (Democratic) appointees? Second, does the presence of a single out-party judge change how a panel relies on earlier decisions compared to what one would expect from a panel with homogeneous partisanship? Finally, does the size of these potential partisan effects change over time in a way that would be consistent with partisan polarization on the courts? We find that partisanship does, in fact, structure whether earlier opinions are followed and that these partisan effects have grown over time—particularly within the subset of cases that we believe are most likely to be ideologically salient. Since legal doctrine is developed by building upon or diminishing past opinions, these results have important implications for our understanding of the development of the law.