Friends You Can Trust: A Signaling Theory of Interest Group Litigation Before the U.S. Supreme Court

• Date: 01 September 2017
• DOI: http://doi.org/10.1111/lasr.12280
• Published date: 01 September 2017

Friends You Can Trust: A Signaling Theory of

Interest Group Litigation Before the U.S. Supreme

Court

Lucia Manzi Matthew E.K. Hall

How do interest groups influence U.S. Supreme Court justices to vote in favor

of their preferred outcomes? Following prior research on the influence of the

Solicitor General, we develop and expand on the signaling theory of interest

group influence via amicus curie briefs. We argue that an interest group’s

ideological reputation and the nature of the ideological signal it sends in its

brief both function as powerful heuristics that convey information to the justi-

ces depending on the justices’ own ideological preferences. When an organi-

zation files an amicus brief advocating for an outcome seemingly contrary to

its traditional preferences (i.e., an unexpected signal), this signal should be

more noticeable and credible than a signal in accordance with a group’s con-

ventional views (i.e., an expected signal). However, unexpected signals should

have greater influence on justices who share the brief filer’s preferences. We

test our signaling theory on the terms from 1991 through 2002. We find that

unexpected signals (but not expected signals) are associated with Supreme

Court voting, and the influence of unexpected signals appears to be particu-

larly strong among justices who share the ideological preferences of the brief

filer.

The rising number of amicus curiae briefs filed in the U.S.

Supreme Court has attracted increased scholarly attention to the

effect of interest group advocacy on the Court. The substantial

and growing participation by amici suggests that interest groups

believe these activities are influential, and empirical evidence sug-

gests they might be right. Earlier research shows that Supreme

Court justices rely so heavily on information in amicus briefs,

that they often signal their need for these documents to interest

groups (Hansford and Johnson 2014). Moreover, previous works

have found that amicus briefs do not just influence the justices’

final decisions on the merits of a case (Box-Steffensmeier et al.

The authors presented an earlier version of this article at the 2014 Midwest Political

Science Association Annual Meeting. The authors wish to thank Ben Denison, Paul J. Hig-

son, Ana Petrova, Nate Sumaktoyo, and Dwight B. King for their help and support. The

authors would also like to thank the four anonymous reviewers for their helpful

comments.

Please direct all correspondence to Lucia Manzi, Department of Political Science, Uni-

versity of Notre Dame, Notre Dame, IN 46556; email: lmanzi@nd.edu.

Law & Society Review, Volume 51, Number 3 (2017)

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C2017 Law and Society Association. All rights reserved.

2013; Collins et al. 2013, 2015), they also affect the justices’ deci-

sion to hear a case in the first place, namely to “grant certiorari”

to a legal case coming from a lower court

1

(Caldeira and Wright

1988; Owens and Black 2011). In addition, other studies suggest

that amicus briefs may have a significant effect on the likelihood

of dissenting opinions (Collins 2008a). Finally, the influence of

amicus briefs appears to extend to all justices across the ideologi-

cal spectrum (Collins 2008b). Nevertheless, the nature of their

influence remains the topic of much disagreement among schol-

ars. Why are amicus curiae briefs so influential? Do all interest

groups stand the same chance of influencing all of the justices, or

are some groups better positioned to influence certain justices in

certain ways?

We address these questions by extending Baily, Kamoie, and

Maltzman’s (2005) signaling theory beyond the Solicitor General

to all interest groups filing amicus curie briefs in the U.S.

Supreme Court. Specifically, we argue that amicus participation

functions as a heuristic signal: Every amici sends a signal to mem-

bers of the court, which includes heuristics, or “mental shortcuts,”

based on the filer’s ideological preferences in relation to the justi-

ce’s preferences and the brief ’s ideological position on the case.

These heuristic signals help the justices deal with the high num-

ber of amicus briefs by allowing them to quickly and easily iden-

tify credible information.

Consequently, an interest group’s ability to influence a justice

depends on the group’s ideology, the justice’s ideology, and the

nature of the ideological signal sent by the group. Justices are

particularly inclined to trust interest groups that share their ideo-

logical preferences and interest groups advocating outcomes con-

trary to their traditional ideological preferences. Amicus briefs

should be especially likely to influence justices when both condi-

tions are present; i.e., a justice and brief filer share ideological

preferences and the brief filer sends an unexpected ideological

signal. As a result, influential legal advocacy only partially

depends on an interest group’s inherent features (i.e., its ideol-

ogy); amicus influence also depends on a specific litigation strat-

egy (sending unexpected signals) and the nature of the signal

receivers (the justice’s ideology).

The U.S. Supreme Court offers an ideal venue to test our sig-

naling theory of interest group influence for several reasons.

First, the highly formalized and routinized process of amicus fil-

ing renders lobbying activities easy to observe and measure.

1

The U.S. Supreme Court chooses the cases it wants to hear. In order for a case to be

accepted for review by the Supreme Court, a majority of justices has to vote in favor of

accepting the case, or to “grant certiorari,” in the legal jargon of the Supreme Court.

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