The development within the field of criminal law is characterized by transnational tendencies taht have become manifest in the interaction between the legal orders of the nation States and various inter- and supranational legal systems.
In Europe, domestic criminal law has become significantly influenced by initiatives originating from the EU, the Council of Europe and the UN. A still more prominent trend is the internationalization of crimes which were formerly within the prerogative of national jurisdictions, inter alia terrorist financing, money laundering, financial fraud etc. The spill-over of such crimes over the borders has led to competing jurisdictional challenges as to where and how such crime shall be criminalized and adjudicated. Consequently, there has been an unprecedented development in the field of transnational crimes which has been reflected in a string of international and EU instruments and in the practices of various international organizations (World Bank, IMF, FATF, EuroJust etc). In particular, the EU commitment to developing an area of freedom, justice and security with as focus on cross border police cooperation and judicial cooperation in criminal matters has become a still more intense.
The increasingly important field of international criminal justice has been sustained by the work of international criminal courts and tribunals over the past two decades. The unforeseen renaissance of international justice in the 1990s revived the importance of legal findings reached by the justices of the Allied Powers in Nuremberg, and attested to the fact that no person regardless of social ranks and positions enjoys impunity for the crimes of great concern to the international community. The adjudication of international crimes, such as genocide, war crimes and crimes against humanity in the ad hoc tribunals for the former Yugoslavia (ICTY) and Rwanda (ICTR); hybrid tribunals for Sierra Leone (SCSL) and Cambodia (ECCC) as well as in the permanent International Criminal Court (ICC), has led to the expansion and revision of substantive and procedural rules which govern the work of aforementioned judicial institutions. These developments has brought back or lent new urgency to a number of concepts of international criminal law: the crime of aggression in the aftermath of the ICC Review Conference in Kampala, the crime of terrorism in light of the latest early jurisprudence of the Special Tribunal for Lebanon (STL), and the crime of piracy given the pressing need to combat this crime off the Horn of Africa. The growing acceptance by the international community of the need to address the most despicable crimes through fair judicial means has brought some comfort and satisfaction to the victims and their communities who suffered from the bitter consequences of conflicts worldwide. International criminal law has been developing inder the influence of major legal systems characterizzed by very diverse and not easily merged legl traditions, e.g. regarding mens rea, criminal paticipation, evidence requirement and other procedural elements.