The Amicus Game

Abstract

Despite increased scholarly attention toward analyzing the influence of amicus briefs on case outcomes, we lack a microfounded model for understanding what we observe. Our analysis remedies this gap, modeling a world in which potential filers can advocate for a particular ruling and may provide information to influence a judge’s decision. We show that the influence of an amicus brief depends on the interaction of the group’s bias and contextual factors. Specifically, while the influence of biased groups is sensitive to features of each case, such as the stakes of the issue, moderate group influence is relatively stable. Our findings are also relevant for empirical studies; they indicate that analyses of influence with observational data are likely undermined by a failure to account for strategic group behavior. Notably, analyzing only filed briefs will generate biased estimates of influence unless the researcher accounts for a group’s interest in each particular case.