The article examines the place and function of prosecution in matters falling within the subsidiary jurisdiction of international criminal courts. It is argued that the emergence of a distinct class of cases concerning offences against the administration of international justice has given rise to a subsidiary layer of jurisdiction and, with it, to a set of specific models for discharging the prosecutorial function. Drawing on the practice of international criminal tribunals and the International Criminal Court, the author traces the evolution of the bearers of that function: from judges relying on their inherent powers to respond to attacks upon the judicial process, through the offices of the prosecutor, to the court appointed amicus curiae prosecutor. The article contends that the present configuration of prosecution in subsidiary jurisdiction cases remains fragmented and essentially reactive in character, and advances the view that further specialisation and institutional consolidation of this function are needed if international criminal justice is to be effectively shielded from offences directed against its very administration.