This book is a collection of updated and thoroughly revised presentations from three international conferences organised within the Jean Monnet project entitled “Three Conferences on EU Criminal Justice: Fundamental Rights, Investigation Measures and the Future European Public Prosecutor’s Office – EUJuCo” by the University of Catania, between September 2015 and February 2017, at the Department of Law and the Siracusa International Institute for Criminal Justice and Human Rights. In line with the project—for the benefit of scholars, students and practitioners of law—this book presents, first of all, some contributions dedicated to the Directives, and their domestic implementation, which have progressively reinforced the cornerstone of procedural rights of suspects and defendants in criminal proceedings in the EU Member States so as to facilitate judicial cooperation (Part I). So, it is in this necessary framework that the following contributions must be placed concerning investigative measures and evidence in transnational criminal proceedings, which have to be seen as a cross section of the current state of judicial cooperation in the area of freedom, security and justice, with the related issues of efficiency, coordination, settlement of conflicts of jurisdiction and guarantees (Part II). Lastly, the contributions in the final part concern emblematically the prospect of a supranational justice system, presenting the legislative proposal for the establishment of the European Public Prosecutor’s Office and its developments. By the time this Jean Monnet project had already been concluded, the proposal, by means of “enhanced cooperation”, took the form of EU Regulation 2017/1939, which the contributions naturally take into account (Part III). The editors trust that these essays, also thanks to the proven expertise of their authors, might stimulate critical reflection on a protean and continually evolving subject.