Despite the fact that amicus curiae participation is the most common method of interest group activity in the judicial arena, there is little consensus as to whether this means of participation influences the decision making of the U.S. Supreme Court. To redress this state of affairs, this research investigates the affect of amicus briefs on the ideological direction of the Court's decisions, with particular attention given to theoretical and methodological issues that have gone unexplored in previous studies. Analyzing group influence during the 1946 to 1995 terms, the results provide particularly robust evidence that pressure groups are effective in shaping the Court's policy outputs. These findings therefore indicate that elite decision makers can be influenced by persuasive argumentation presented by organized interests.
Keywords: Supreme Court; interest groups; pressure groups; amicus curiae
Interest groups are a mainstay in American politics. In their most quixotic form, representatives from pressure groups filled the smoky hallways of the House and Senate patiently waiting for representatives and senators to emerge and willingly hear from the voices of the citizenry. While pressure politics have lost much of this sense of romanticism, due in part to allegations of scandal and corruption, interest groups nonetheless remain a permanent force in Washington politics. And despite the fact that groups are most commonly associated with the elected branches of government-be it through the financing of political campaigns, the dissemination of information to executive agencies, or the everyday lobbying of congresspersons-groups nevertheless play a major role in judicial politics, particularly at the Supreme Court. By setting up test cases and sponsoring cases that others bring into the appellate stages, organized interests are a visible force in the judicial arena. Although interest groups pursue the aforementioned methods with some regularity (e.g., Epstein and Rowland 1991; Wasby 1995), the predominant method of interest group participation in the courts is filing amicus curiae briefs (Caldeira and Wright 1988; Collins 2004). As "friends of the court," groups present jurists with legal, policy, and social scientific information aimed at the broader policy ramifications of a court's decisions. Furthermore, despite the fact that the name implies neutrality, amicus briefs are, in truth, adversarial, almost always urging the courts to endorse a particular policy outcome (Banner 2003). While amicus participation is a common occurrence in lower federal courts (e.g., Martinek 2006) and state courts of last resort (e.g., Songer and Kuersten 1995), the most prevalent venue for amicus participation is the U.S. Supreme Court. In recent terms, more than 90 percent of the Court's cases were accompanied by amicus filings (Kearney and Merrill 2000).
Given the frequency with which groups participate in the Supreme Court, it should not be surprising that scholars have dedicated a great deal of research to examining whether these briefs influence the choices justices make (e.g., Collins 2004; Epstein 1993; Heberlig and Spill 2000; Ivers and O'Connor 1987; Kearney and Merrill 2000; McGuire 1990, 1995; O'Connor and Epstein 1982, 1983; Samuels 2004; Songer and Sheehan 1993; Spriggs and Wahlbeck 1997; Vose 1955, 1959). While there is compelling evidence that amicus briefs influence the justices' decisions to grant certiorari (Caldeira and Wright 1988), there is little consensus as to whether amicus briefs influence the justices' decisions on the merits (McLauchlan 2005, 10; McGuire 2002, 156; Segal and Spaeth 1993, 241; Stumpf 1998,401; Walker and Epstein 1993, 139). This confusion has manifested itself for a number of reasons.
First, many of these studies have examined only a few groups (e.g., Harper and Etherington 1953; Ivers and O'Connor 1987) or issue areas (e.g., McGuire 1990; O'Connor and Epstein 1982). While these studies may provide valuable theoretical insight into interest group impact on the Court (e. …