Because mutual recognition is now enshrined in the Lisbon Treaty as a basic principle for judicial cooperation in criminal matters, a consistent interpretation and application becomes all the more important. Nevertheless, no legally binding definition of mutual recognition is provided and a quick scan of the relevant instruments cannot but lead to the conclusion that mutual recognition appears in as many shapes and sizes as there are instruments referring to it. There seems to be no common understanding of what mutual recognition is, can and cannot be and how consistency is to be guaranteed. Therefore this article critically reviews mutual recognition as a principle and assesses
the inconsistencies in the application thereof. The analysis is based on two hypotheses that could clarify the divergent evolution of the principle. The first hypothesis to explain the divergent evolutions is linked to the action radius and the proposition that mutual recognition is the cornerstone of judicial cooperation only. The second hypothesis suggests that the reason for these divergent evolutions is the lack of a common understanding of what mutual recognition entails, what it means or should mean in practice. Based on a thorough analysis of the relevant policy documents, treaties and judicial cooperation instruments (including their preparatory documentation and transcripts from debates in various fora) it is recommended to no longer distinguish between police, customs and judicial cooperation and move ahead with the introduction of mutual recognition as a basic principle for international cooperation in criminal matters in its entirety. Furthermore, the suggestion is made to introduce a lex mitior principle as a new automatic correcting mechanism to temper the effect of mutual recognition from the perspective of the persons involved.