The transnational gathering and use of criminal evidence is a complex and sensitive matter that affects basic principles inherent in national criminal justice systems. Replacing the mutual assistance regime (letters rogatory) by a mutual recognition regime intends to facilitate the admissibility of evidence obtained from the territory of another Member State. How much harmonization of criminal procedure is needed to guarantee the free movement of criminal evidence in the EU? Do we have to develop common procedural safeguards in the EU, or can we build in human rights clauses or procedural public order clauses by which respect for fundamental rights can be a ground for the non-recognition, non-execution or postponement of the order from the issuing state? John Vervaele is Professor in Economic and Financial Criminal Law at the University of Utrecht and Professor in European Criminal Law at the College of Europe of Bruges. The main topics in his research field are: enforcement of Union law; standards of due law, procedural safeguards and human rights; criminal law and procedure an regional integration; comparative economic and financial criminal law. He has realized a lot of research in these areas, both for Dutch Departments and European Institutions and also worked as a consultant for them.