International criminal justice is based to a large extent on extrapolations from criminal-law research on domestic systems. The difficult exercise of arriving at a common denominator is exacerbated by the systemic dichotomy of the so-called common-law and civil-law models, which, in turn, have now been joined by a third contender: public international law. Each of these has its own methods of approaching the task of solving legal problems. This paper queries the inter-model conversation that is happening so far and asks the question as to whether it is necessary to hold this discussion at a much more fundamental level than it would seem has been the case so far. It does so at the example of the relationship between German and English and Welsh law, but its concerns and conclusions merit consideration for the entire debate between the systems.