Studies show will stick to precedent

While the Spaeth and Segal study cast serious doubt on the influence of stare decisis, it nevertheless demonstrated that it exerts some force, even in those instances where it is least likely to – that is, where a justice has directly considered and previously rejected a ruling. Studies coming at precedent from different angles have contributed additional evidence that precedent matters.

Hansford and Spriggs (2006), for example, found that the “vitality” of precedent, important to federal district and circuit judges, also counts with the justices themselves: they are more likely to accord positive treatment to precedents that have previously been treated positively by the Court. Bailey and Maltzman (2011), employing highly sophisticated measures of justices’ ideologies and the ideological implications of the cases before them, tested whether justices were responsive to precedents in cases where those precedents were seriously contested. They found that the precedents exerted significant effects on the decisions of some, though not all, justices.

Other studies of precedent have begun by recognizing that precedent can operate subtly and indirectly, not so much directing judges to a particular answer as guiding them to think about problems in certain ways or to give more or less weight to certain considerations. Richards and Kritzer’s (2002; Kritzer and Richards 2003) analyses of legal “regimes” centered on key cases that shifted doctrine in major areas of constitutional law. The authors found that the effects of various case factors on justices’ votes changed in the ways suggested by those key cases, indicating that justices allowed precedent to shape the way they approached cases.

Even the subtle method of Richards and Kritzer requires a researcher to make judgments about the content of the law in order to determine whether judges are responding to it. Bartels (2009) largely avoided this difficulty in his study of First Amendment decision making, though at the expense of requiring a greater inferential leap. He assessed the role of ideology in justices’ decisions before and after a key decision establishing that “content-based” restrictions on speech, unlike “content-neutral” restrictions, should be subjected to strict scrutiny. Because strict scrutiny reduces judges’ discretion, application of it should attenuate the influence of ideology. Bartels’ finding that ideology did not predict voting as well in cases involving content-based restrictions suggests that justices take the law in this area seriously.

If willing to take an even less direct approach, one can look for evidence of law’s effect in the influence of other actors on judges. For instance, consider the exceptional litigation success of the Solicitor General’s office (Black and Owens 2012) and other highly experienced Supreme Court lawyers (McGuire 1993), success that cannot be explained entirely by the strategic (or lucky) choice of positions that the justices already favor. A highly plausible explanation of this success is that the justices take these lawyers’ arguments more seriously than other lawyers’, whether because greater experience and skill yields superior arguments or because they earn the justices respect and trust over time.

Recent studies in this spirit include Lindquist and Klein (2006) and Collins (2008). Lindquist and Klein, investigating legal issues that had divided lower courts, found that the Supreme Court was more likely to choose the position supported by a larger number of circuits and by more highly regarded circuit judges. Collins, analyzing all cases with identifiable liberal and conservative positions, found that justices were more likely to vote in favor of the position supported by more amicus curiae briefs. These findings, like those on lawyer success rates, could conceivably be explained in attitudinal terms: the justices might find their arguments convincing on policy, rather than legal grounds. But this reading is implausible for precisely the reason policy attitudes play such an important role at the Supreme Court – because they are typically so strong and easily accessible in the cases the justices hear. Especially as all of these studies controlled for justices’ ideology, among other things, it seems more reasonable to view the findings as evidence that the justices are moved by legal reasoning.2