This dissertation explores the nature and extent of amicus curiae participation and impact at the Roberts Court. While previous literature has addressed amicus activity and influence in prior eras of the Court, in specific issue areas, and in specific cases, none has focused in a systematic way on the Roberts Court. Compiling data from the 2007-08 through 2011-12 terms of the Roberts Court, this study first examines the levels and categories of amicus participation during this time period. Amicus activity at the Roberts Court is ubiquitous, and exhibits an “arms race” phenomenon, being relatively ideologically balanced.
Second, this study analyzes the impact of amici on the ideological direction of the justices’ votes at the Roberts Court. To address this topic, a number of statistical models are estimated, controlling for other known influences on judicial decision-making. The results demonstrate that amicus briefs positively impact the direction of justice votes across the ideological spectrum in both routine and politically salient cases. When, how, and to what degree amicus briefs matter depends on the level of amicus brief disparity, the ideology of the justice, the issue area of the case, and the prestige of the amicus participants involved. The greater the amicus brief advantage in a case, the greater the amicus influence. Moderate justices, as a rule, are more influenced by amicus briefs than more ideologically extreme justices. However, unlike amicus briefs, an advantage of amicus cosigners in a case typically does not impact the direction of the justices’ votes.
These findings shed light on the larger debate in the judicial behavior literature regarding whether justice votes are simply a result of judicial attitudes (attitudinal model), or if legal rules and arguments (legal model), and/or public opinion (interest group model) shape judicial decision-making. While affirming that judicial attitudes are the most significant predictors of the justices’ votes, the results indicate that the legal persuasion model best describes amicus influence. Amicus curiae briefs matter for the relevant information they provide to the justices, and most justices, regardless of ideology, are impacted by this information
