Experts often seek to apply social science to the facts of a particular case. Sometimes experts link social science findings to cases using only their expert judgment, and other times experts conduct case-specific research using social science principles and methods to produce case-specific evidence. This article addresses the scientific and legal merits of these two approaches and argues for the use of methodologically rigorous case-specific research to produce “social facts,” or case-specific evidence derived from social science principles. We explain the many ways that social fact studies can be conducted to yield reliable case-specific opinions, and we seek to dispel the view that litigation poses insurmountable barriers to the conduct of case-specific empirical research. We conclude that social fact studies are feasible for both plaintiffs and defendants, with or without special access to the parties involved in a case, and provide much sounder conclusions about the relevance of social science to a litigated case than do alternatives based on expert judgment.