Legal practitioners and courts deploy, apply, and adjudicate evidence concepts daily. Yet, the United States legal profession rejects efforts to generate rigorous empirical evidence about itself–evidence that would inform day-to-day practices. To justify its resistance, the profession recites arguments identical to those articulated in the 1940s by interest groups resisting medicine’s then-evolving insistence on randomized evaluation of new drugs. Why does the U.S. legal profession resist rigorous empiricism? And what can be done about it?