This article examines the Supreme Court's use of social science research evidence in 28 capital punishment cases decided between 1986 and 1989. The study describes the frequency and major correlates of the justices' citation of social science authorities in the 1986–89 sequence of cases. Social science evidence figured significantly in several death penalty cases, although a majority of the justices were more eager to discredit and discount research conclusions than to use them as premises for their decisions, and prevailing case opinions generally promoted principles that had little to do with empirical evidence concerning the administration of capital punishment. Social science citation patterns in majority and dissenting opinions, and in the opinions of “liberal” and “conservative” Supreme Court justices, in significant respects parallel the Court's shifting doctrinal premises in capital punishment decisions.