Understanding the source of voting changes by appellate judges provides an important window into the factors that shape the votes of the judges more generally. We argue that membership changes, by altering the collegial context in which judges make their choices, affect the information environment, long-term collegial considerations, and short-term strategic calculations. As a result, membership change should lead to greater uncertainty and more frequent voting changes among continuing justices in the term following a replacement. We test this proposition by looking at vote change by justices of the U.S. Supreme Court in two separate analyses: justices' votes on search-and-seizure cases since Mapp v. Ohio (1961) and on the progeny of Miranda v. Arizona (1966). Our results support the argument that the collegial context helps explain changes in voting choices. Our analysis suggests that collegial considerations are an important component of judges' behavior and merit further evaluation in a cross-national context.
Theoretical perspectives on judicial behavior provide good reason to expect that collegial court judges-across courts, nations, and levels of the judiciary-are subject to intracourt influence. Judicial scholars know that, despite the importance of ideology, the collegial context in which judges decide cases has a significant effect on how their preferences are expressed. On rare occasions, judges can be quite forthright about the influence their colleagues have on their behavior, offering important insights into what factors influence their behavior. Tom Clark, a U.S. Supreme Court justice from 1949 to 1967, offered such an insight into his decisions leading up to the Court's landmark Mapp v. Ohio (1961) decision. Just before Clark became a justice, the Court decided Wolf v. Colorado (1949). In that case, a six-justice majority declined to extend the exclusionary rule (suppressing evidence obtained in an illegal search) to the states. Through the 1950s, Court majorities held to diis position, and Justice Clark joined these majorities. But in 1961, Justice Clark wrote the majority opinion in Mapp v. Ohio, reversing both Wolf and his own earlier support of that precedent. Justice Clark's writings help explain this interesting reversal. In Irvine v. California (1954), which upheld Wolf, Clark offered the following observations in a concurring opinion:
Had I been here in 1949 when Wolf was decided, I would have applied the doctrine of Weeks v. United States, 232 U.S. 383 (1914), to the states. But the Court refused to do so then, and it still refuses today. . . . [I]t is with great reluctance that I follow Wolf. Perhaps strict adherence to the tenor of that decision may produce needed converts for its extinction (Irvine v. California, 347 U.S. 128, 138 ).
Justice Clark's unusually candid reflections nicely illustrate the quandary that collegial court judges face: their ability to affect decisions rests not only on their own preferences but also on their ability to convince their fellow judges of the merits of their position. In Justice Clark's case, building a majority required both the appointment of new justices allied with his sincere preference and the conversion of continuing justices (Schubert 1962:91-2).
The experience of Justice Clark on the U.S. Supreme Court has been buttressed by scholarly findings in a variety of environments. For example, several scholars have concluded that under some circumstances, female judges behave differently from male judges (see, e.g., Allen & Wall 1987; Songer et al. 1994), and the presence of female judges may even change the behavior of male judges (O'Connor & Segal 1990, but see Palmer 2002). Judges are concerned about the esteem of their colleagues (Baum 2006) and may alter their behavior in order to secure respect. Judges are also frequendy characterized as strategic actors; if they are concerned about the ultimate content of policy, they may take account of the anticipated behavior of their colleagues. …