Because national judges and police officers cannot act beyond their respective borders, states have methods on interstate cooperation in criminal matters designed to overcome these difficulties. The simplest and most common method is that of mutual legal assistance, in which the requested state carries out action on behalf and at the request of another state for purposes relating to proceedings. Many methods of cooperation are autonomously identifiable and separately regulated both in domestic and international law, including extradition, which is the surrender of a person by state A to state B, at the request of state B. Extradition is done for the sake of reciprocity. Where reciprocity is not guaranteed, extradition is not possible. Foreign prisoners encounter difficulties on account of such factors as different language, culture, customs, and religion. The problems of communication and the necessity to take account of their special needs and problems place an additional burden on prison administrations. The Convention of the Transfer of Sentenced Persons studied problems relating to the treatment of foreigners in prison and considered drawing up a model agreement for the transfer of foreign prisoners. The purpose is to facilitate the transfer of foreign prisoners to their home countries in order to serve the remainder of their sentences by providing a simple and expedient procedure. In facilitating the transfer of foreign prisoners, the convention takes account of modern trends in crime and crime policy. Either the sentencing state or the administering state may request transfers. The first condition is that the person to be transferred is a national of the administering state. The second is that the judgment must be final and enforceable. The third condition concerns the length of sentence still to be served. The fourth condition is that the person concerned must consent to the transfer. The fifth condition is intended to ensure compliance with the principle of dual criminal liability. The sixth condition is the agreement of the sentencing state. The seventh condition is the agreement of the administering state. 3 footnotes