The European Union has proposed a European Investigation Order to facilitate the transfer of evidence between member states. Ryan has suggested that “[t]he creation of a European Community wherein persons, goods and capital could move freely between borders brought with it new opportunities for the free movement of crime” . This thesis sets about investigating how the European Union institutions legislating for the transfer of evidence may affect the criminal process in Ireland and in particular the right to a fair trial and protection of fundamental rights. The European Criminal Process is examined. The history of the criminal justice competency of the EU is detailed. The roles played by various European institutions in the criminal process are considered. Important principles such as mutual legal assistance and the stronger principle of mutual recognition are considered, as are human rights within the EU. Evidence exchange and in particular the European Investigation Order is considered. A chapter considers the rationale/demand for the creation of the EIO including looking at the objectives of the European Investigation Order. This chapter outlines the current procedures in place at an EU level and compares them against the proposed operation of the EIO. The Irish approach to the exclusion at trial of improperly obtained evidence is compared with that of other EU countries. The traditional modes of trial (inquisitorial and adversarial) are compared first. The exclusionary rule of evidence will be used to compare how numerous European jurisdictions deal with evidence which is improperly obtained. It is hoped that by the end of the thesis, the reader will have an understanding of the developing European criminal process and the new European Investigation Order. It is intended to consider whether or not the EIO would be suitable for adoption by Ireland.