Amicus curiae and the role of information at the Supreme Court

Conventional wisdom holds that amicus briefs provide the Supreme Court with information that is not otherwise supplied by litigants and that the Court finds this information useful. While several studies explore the information that amici contribute to the Court in certain notable cases, judicial scholars have no systematic knowledge regarding the nature of information furnished by amici or the Court's use of it in its opinions. We argue that amici curiae briefs are important because they reduce information problems at the Court by helping the justices anticipate the impact of their opinions. To test conventional wisdom, we examined all party briefs on the merits and amicus briefs filed in the 1992 term. We found that the conventional wisdom is largely inaccurate. First, amicus briefs often contribute unique arguments, but they also commonly reiterate their party's brief. Second, the Court's majority opinions are not more likely to use arguments from amicus briefs that offer new information. In fact, the Court is much less likely to adopt arguments from amicus briefs that exclusively add arguments not found in their party briefs, even after controlling for a variety of alternative explanations. The implication is that amici influence is not a function of the independent information they convey.