Records on the trial and sentencing for heresy of French warrior Joan of Arc dating to 1431 have been studied by a variety of fields. The present work explores the primary sources and several of these studies in the aim of analyzing the political significance of the forms adopted during the trial. From a perspective poised between the history of law and procedural law, the article clarifies aspects of the practical functioning of the Roman Canon inquisitorial procedure at the end of the Middle Ages, and, more widely, the phenomenon of the capillarization of the political power by means of the production of truth. The article concludes that, although Joan of Arc’s trial was clearly politically motivated, several of its dimensions correspond to the procedural practices of the time, leading us to an understanding that the influence of power over trials does not necessarily manifest in a direct violation of procedural rules, but rather in their very design and the ways in which they are put into operation.