purpose of the study Judicial cooperation in criminal matters within the EU is based on the principle of mutual recognition of judicial decisions and approximation of Member States’ criminal laws. The EAW and the three Framework Decisions related to detention, are instruments created in an effort to improve judicial cooperation in the EU and to ensure an equal treatment of non-residents and residents in criminal proceedings. Their implementation is based on the principle of mutual trust, which implies that conditions of detention and procedural safeguards are equivalent in every State. In reality, however, discrepancies exist, which potentially raise significant fundamental rights concerns. The poor implementation of the Framework Decisions have been highlighted by the European Commission, in its implementation report of February 2014, stressing the need for improvements and harmonisation among Member States.3 The European Commission stated that the rules “have the potential to lead to a reduction in prison sentences imposed by judges to non-residents. This could not only reduce prison overcrowding and thereby improve detention conditions, but also – as a consequence – allow for considerable savings for the budget spent by Member States on prisons.”4 The European Commission’s Green Paper on Detention notes that prison overcrowding and allegations of ill-treatment may undermine the principle of mutual trust. Ensuring mutual trust between Member States is still viewed as an important challenge to overcome, as it would imply that conditions of detention and procedural safeguards are equivalent in every State, while discrepancies prevail in reality. Therefore concerns exist with regard to ensuring that Art. 3 ECHR obligations are adhered to when national authorities implement EU legislation. Member States furthermore highlighted the practical difficulty of finding updated information concerning prison conditions and criminal justice systems of other Member States.”5 This was recently addressed in a judgment that was delivered in the CJEU in April 2016. In that decision which concerned the surrender of two individuals on foot of an EAW, concerns were raised as to the prison conditions of the issuing state, and the resultant article 3 ECHR implications. The Court held that where judicial authorities are in possession of evidence of a real risk of inhuman and degrading treatment, the executing judicial authority must obtain information on prison conditions in the issuing member states and directed national courts to judgments of the ECtHR, decisions and reports of CoE and UN bodies, and furthermore to consider the information obtained from national monitoring mechanisms mandated to visit detention facilities.6 National Preventive Mechanism (NPMs), established in accordance with the Optional Protocol to the UN Convention against Torture (OPCAT), could therefore play an important role in addressing fundamental rights challenges linked to the implementation of the EAW, the Framework Decisions on Detention and other relevant EU legislation. NPMs regularly monitor places of detention, provide State Parties with systematic observations and recommendations on the treatment and conditions in detention, thus increasing the protection of detainees against torture. Currently 24 NPMs have been established within the EU, which carry out monitoring visits and provide valuable expertise regarding the situation in their countries. Comprehensive research carried out at the BIM in the framework of a previous EU-funded project has shown that there is little interaction between judges 3 Report from the Commission to the European Parliament and the Council on the implementation by the Member States of the Framework Decisions 2008/909/JHA, 2008/947/JHA and 2009/829/JHA on the mutual recognition of judicial decisions on custodial sentences or measures involving deprivation of liberty, on probation decisions and alternative sanctions and on supervision measures as an alternative to provisional detention (COM (2014) 57 final) 5 February 2014. 4 Ibidem p.12. 5 Analysis of the replies to the Green Paper on the application of EU criminal justice legislation in the field of detention, p.8 6 Joined Cases C‑404/15, Aranyosi and C‑659/15 PPU, Caldӑrӑru [2016] paras. 88 -89. 14