This article explores the “fair trial”as a good practice for the construction of public proof. If proof signifies closure on matter(s) at hand, and publicness is taken to signify both “access to”and “participation in”the construction of proof by the publics concerned, the authors contend that the “fair trial”is a good example of building public proof and that its backbone constraints can be of great interest to the defenders and advocates of participative Technology Assessment (pTA), especially citizens’juries.