Legal proof comes under scrutiny in theatrical criminal trials in early seventeenth-century England. I maintain that probability is a bundle of related concepts that have received different emphases in different cultures at different times; that the practice of adjudicating alleged crimes via England's adversarial, jury-oriented, and performance-based system involved both established and emerging concepts of probability; and that plays including Ben Jonson's Volpone, John Webster's The White Devil, and Shakespeare's Measure for Measure expressed some of the tensions concerning these differentiated notions and the practices that relied on them. Practices consistent with the modern meanings of probability were already present in the law courts of early modern England, though they were articulated according to older, rhetoric-based definitions of probability or labeled as something other than probability. This elasticity in the way probability is conceived and put to use shows up in the three plays under consideration here. Volpone mocks the tools which triers of fact use to gauge witness credibility-oathtaking, consideration of reputation, expectations about how guilty or innocent people "act" in court-and satirizes the expectations that jurors share about what guilt should look like and the "show" the accused should put on, thus incarnating an everyday kind of "expectation" probability that becomes the focus of the mathematicians' attempts to devise a calculus modeled on "the reasonable man" later in the seventeenth century. In The White Devil the drawing of inferences from circumstantial evidence in Vittoria's trial invokes the same kind of probabilistic reasoning which supposedly bolsters jury verdicts, yet the performativity of her testimony complicates the probability underlying law's epistemology of near-certainty. Measure for Measure reifies the epistemological or degree-of-belief probability inherent in the emerging standard of proof-the "satisfied conscience," yet in the depiction of the processes of judgment also explores a skeptic's argument against law's claim to near-certainty.