After a historical review of the use of psychological data in death penalty litigation and a discussion of why it once promised to play a unique role in such litigation, the authors assess the Supreme Court's record in using and evaluating psychological data over the past two decades. They show a period of conflict between law and social science in capital jurisprudence that has been marked by increasingly well- documented empirical realities of and competing doctrines and opinions on capital punishment. The Supreme Court has articulated constitutional rules that render social science data irrelevant to the legal question at hand. Although the Supreme Court's contempt for empirical data regarding the death penalty has left social science researchers still interested in capital jurisprudence with significantly limited constitutional arenas in which to present their findings, it has not eliminated all of their critically important roles in capital litigation. Social science scholars can still assist lawyers who are working to affect State legislation on death penalty issues or who are litigating discriminatory practices in jury selection and prosecutorial charging practices in death penalty cases at the local level. Social scientists are still needed in individual trials to provide evidence about the devastating effects of family violence, child abuse, drug abuse, poverty, and racism, all classic issues in the lives of most persons facing the death penalty. 88 references