Brian Simpson argued that any general explanation for why states accede to international humanitarian treaties can only be valuable if based empirical case studies. His meticulous study of the British Government papers on the Genocide Convention reveal the “hidden practices” behind the British Government’s time lag in acceding to the Genocide Convention, a treaty negotiated only a few years after British involvement in the Trial of the Major War Criminals, better known as the Nuremberg Trials. As Carty notes, political events involve a powerful blend of counter-positions and political spin and consequently, given the rhetoric used by states, the hidden practices are challenging to deduce or construct as they are ‘largely secret and one obtains only sporadic glimpses of [them]’.Therefore, studies on contemporaneous state conduct are hampered by the very fact that the events are ongoing. However, when state archives reveal those hidden practices, they permit wonderfully rich empirical studies of state conduct during critical historical moments. Inspired by Simpson’s investigation, this paper provides an empirical case study of Irish Government papers on the Genocide Convention. Its purpose is to investigate why Ireland delayed accession to the Genocide Convention for over two decades, why the Irish Cabinet eventually decided to accede in 1968 and why there was a continuing delay until ratification in 1976. It demonstrates how each of the critical elements, identified in Simpson’s study, varies in significance in the Irish case study. Here, in contrast to their British counterparts, Irish Government departments were more cohesive on issues of doctrinal law and on their political analysis of the Convention. Status-oriented concerns were acutely influential for External Affairs and over time, its officials persuaded Justice and the Attorney General’s Office that Ireland’s standing within regional and global communities was critical and dependent on a more positive human rights treaty image. Although domestic pressure among Irish parliamentarians and NGOs was very limited until the early 1970s, it provided Foreign Affairs with useful incentive for in their deliberations with other departments. Finally, similar to the British engagement, bureaucracy, political leadership and doctrinal law were all significant factors.