The 'political history of truth' promoted by Foucault reaches several times ancient Greek world. In one of those occasions he analyses Oedipus the King, by Sophocles. His point of view is consistent with theorists like Jean-Pierre Vernant whereby tragic contests plays a civic function in the environment of democratic polis. This paper discusses Greek judiciary practices and his mechanisms of truth, pointing tragedy as privileged document and possibly watershed. [ABSTRACT FROM AUTHOR]