This essays explores several epistemological related elements in the early modern English jury trial environment. Witnessing, credibility, testimony, doubt, suspicion, equivocation, conscience, fact, and oaths are frequent topics in law and literature studies. In one way or another, all of them raise questions of truth-telling, fact-finding, and epistemology. This environment included oath taking, the credibility of oath and non oath takers, the rhetorical origins of credibility criteria, casuistry, and the legal language of ‘satisfied conscience’, and the interplay between ‘truth’ and ‘mercy.’ It also discusses the consistency, tension, and/ or conflict between conceptual elements and the practices of grand jurors, jurors, and judges.