The Camorra criminal trials, held in Naples, involved more than a thousand people charged with belonging to a criminal organisation, the Nuova Camorra Organizzata (NCO). In the winter of 1982-3 the NCO suffered the desertion of some of its key men who, once arrested, broke the code of silence (omert...), turned against their former associates, and collaborated with the Justice Department. In the initial set of trials their testimony was found sufficiently reliable and convincing to determine the convictions of more than 800 defendants, but in the appeal their credibility was destroyed and the majority of people convicted solely on these witnesses' testimony were acquitted. This study documents the shifting relationship between these witnesses - called pentiti - and the Justice Department. To investigate this dramatic reversal of the defendants' convictions Marco Jacquemet combines analysis of talk and power technologies with a reflection on truth and credibility as communicative representations.