With the advent of international criminal courts and tribunals, there are ne bis in idem provisions that restrict both the international and national courts in conducting subsequent prosecutions. Ne bis in idem rule can apply both horizontally and vertically. However, the function of the latter is to adjust the relationship between international courts and national courts. The vertical ne bis in idem effect include both "downward" and "upward" levels. The content and scope of the rule are not uniformly defined. In particular, ways to interpret the two decisive factors ‘Idem’ and ‘Bis’ vary considerably. In the interpretation of the term “Idem”, there is ambiguity as to what stage former prosecution should be taken place in order to prevent a new prosecution. Another ambiguity relates to the term “Bis”; In fact, what the Bis is and in which circumstances second prosecution is double prosecution. Response to that depends on the test that is used by the court: the same conduct test or the same offense test. This paper by examining statutes and case law of international criminal courts and tribunals concludes that former prosecution had to give rise to conviction or acquittal to prevent a new trial. Depending on the upward or downward vertical Ne Bis in Idem rule, application of both tests is possible.