Friends of the Supreme Court: Examining the influence of interest groups in the United States Supreme Court, 1946--2001

Despite the fact that numerous studies exist examining the influence of amicus curiae participation in the U.S. Supreme Court, there is little consensus that this method of interest group activity actually influences the decision making of the justices. This dissertation remedies this state of affairs by developing a theoretical framework in which the influence of amicus participation is viewed in light of extant theories of judicial choice. Specifically, I consider amicus curiae briefs as sources of legal and political information for the justices and examine whether their influence is mediated by judicial ideology (i.e., dependent upon the congruence of the information in the briefs with the policy preferences of the justices). I also examine the potential for repeat player amici to wield particular influence. I subject my hypotheses to empirical validation by examining the votes of all justices during the 1946--2001 terms, with special attention given to search and seizure and free expression law, two issue areas that allow for particularly rigorous hypothesis testing. The results indicate that, not only do amicus curiae briefs influence the decision making of Supreme Court justices, but also that this influence is not mediated by judicial ideology. As such, amicus briefs are able to persuade ideologically-driven justices to support the positions advocated in the briefs (though the effectiveness of repeat players is uneven). Given this, I interpret the results as evidence that the law matters to the justices. Clearly, the justices' attitudes play a role in their decision making. But, by providing the justices with persuasive communication regarding how the law should be applied in any given case, amicus briefs highlight that decision making on the Supreme Court is more than a function of the justices' attitudes and values. By persuading the justices to adopt positions consistent with the legal argumentation in the briefs, amicus briefs provide us with an insight into one way in which the law matters to Supreme Court decision making.