Between 2003 and 2007 in Argentina a series of legislative and judicial measures were carried out. Those mesures allowed to resume the trial for the crimes committed during the last military dictatorship. To reopen the trials, it was crucial to classify dictatorial crimes as "crimes against humanity". This article analyzes how two attempts to blame the armed organizations -Montoneros for the deaths of the militants who participated in the "Operacion Contraofensiva" and the Ejercito Revolucionario del Pueblo for the murder of Colonel Larrabure- contributed to construct a hegemonic interpretation of that one criminal category.