Friends of the Circuits: Interest Group Influence on Decision Making in the U.S. Courts of Appeals*

Objective. Though there is an extensive literature focused on the participation and efficacy of interest group amici curiae in the U.S. Supreme Court, there is little rigorous analysis of amici curiae in the U.S. Courts of Appeals. Here, we systematically analyze the influence of amicus curiae briefs on U.S. Court of Appeals decision making to provide insights regarding both judicial decision making and the efficacy of interest groups. Methods. We use a probit model to capture influences on appellant success in the courts of appeals from 1997–2002. Results. We find that amicus briefs filed in support of the appellant enhance the likelihood of that litigant's probability of success, but that amicus briefs filed in support of the appellee have no effect on litigation outcomes. Conclusion. Amici can help level the playing field between appellants and appellees by serving to counter the propensity to affirm in the U.S. Courts of Appeals.