On the Nature of Supreme Court Decision Making

How does the U.S. Supreme Court reach decisions? Since the 1940s, scholars have focused on two distinct explanations. The legal model suggests that the rule of law (stare decisis) is the key determinant. The extralegal model posits that an array of sociological, psychological, and political factors produce judicial outcomes. To determine which model better accounted for judicial decisions, we used Supreme Court cases involving the imposition of the death penalty since 1972 and estimated and evaluated the models' success in accounting for decisional outcomes. Although both models performed quite satisfactorily, they possessed disturbing weaknesses. The legal perspective overpredicted liberal outcomes, the extralegal model conservative ones. Given these results, we tested another proposition, namely that extralegal and legal frameworks present codependent, not mutually exclusive, explanations of decision making. Based on these results, we offer an integrated model of Supreme Court decision making that contemplates a range of political and environmental forces and doctrinal constraints.