Jury science is fraught with difficulty. Since legal and institutional hurdles render it all but impossible to study live criminal jury deliberation, researchers make use of various indirect methods to evaluate jury performance. But each of these methods are open to methodological criticism and, strikingly, some of the highest-profile jury research programmes in recent years have reached opposing conclusions. Uncertainty about jury performance is an obstacle for legal reform—ongoing debates about the ‘justice gap’ for complainants of sexual offences has rendered (...) these problems stark. This paper proposes a way to advance the debate. (shrink)