Abstract: Within a few years of Lateran IV’s prohibition of priestly involvement in trial by ordeal, England moved definitively toward a criminal justice system based on trial by jury. This paper will explore the underlying assumptions of king, council and justices at the time of the criminal trial jury’s introduction (c. 1220) as to the jury’s precise function within a prosecutory system that countenanced only capital sanctions for those convicted of felony. Unearthing these assumptions will require careful consideration of earlier ordeal procedure and other kinds of juries in the late twelfth and early thirteenth centuries, most notably juries of presentment, coroners’ inquests, and juries tasked with responding to writs de odio et atia. It will also require situating trial by jury within the broader context of felony adjudication with its manifold escape valves, including benefit of clergy, sanctuary, abjuration and pardons. The paper will rely on a re-examination of primary source materials and engagement with the existing secondary literature to grapple with the broad questions of what constituted serious criminal wrongdoing, what jurors were expected to know and do in adjudicating felony cases, and the extent to which jurors’ verdicts were based on knowledge or belief in the guilt of an individual, as opposed to such factors as reputation, rumor or expected recidivism. With regard to the issue of jury independence, the paper will query whether juries engaged in unilateral nullification of the law, or whether verdicts that appear to be contrary to the law reflect instead a consensus of judge and jury. Related to this is the macro-level question of what constituted the law, including the related matters of how jurors were to know the law and respond to it. As a think piece, this paper will test several hypotheses regarding problems fundamental to the history of English criminal law, some of which may prove unresolvable.