The book is a critical review of accountability conducted under the authority of the United Nations Security Council, by the International Criminal Tribunal for Rwanda (ICTR), and the United Nations Transitional Administration in East Timor (UNTAET). It is centred on two case studies: the 1999 events in Rwanda, which constituted genocide, 'the crime of crimes', and the 1999 mayhem in East Timor. The books subjects to testing cross-examination tools to hold accountable persons with 'the greatest responsibility' for serious international humanitarian law violations. A detailed expose is made of conspiracy to commit genocide. Comparison is also made whether joint criminal enterprise, and the forms of co-perpetration embodied in the Statute of the International Criminal Court provide effective alternatives in the case of atrocity crimes. A unique aspect of the book is its high-light of lessons learn in prosecution strategies; approaches in profiling perpetrators, particularly those with the highest level of responsibility for international humanitarian law violations; victors justice; superior responsibility; guilty pleas, and the effectiveness of the East Timor and the Indonesian Ad Hoc Human Rights Court processes. In the final analysis, the book offers a Matrix on Accountability.