Artikel 12bis

1. A person who is being detained or is serving a sentence in the territory of one State Party whose presence in another State Party is requested for purposes of identification, testimony or otherwise providing assistance in obtaining evidence for the investigation or prosecution of offences set forth in article 3, 3bis, 3ter or 3quater may be transferred if the following conditions are met:
a) the person freely gives informed consent; and
b) the competent authorities of both States agree, subject to such conditions as those States may deem appropriate.
2. For the purposes of this article:
a) the State to which the person is transferred shall have the authority and obligation to keep the person transferred in custody, unless otherwise requested or authorized by the State from which the person was transferred;
b) the State to which the person is transferred shall without delay implement its obligation to return the person to the custody of the State from which the person was transferred as agreed beforehand, or as otherwise agreed, by the competent authorities of both States;
c) the State to which the person is transferred shall not require the State from which the person was transferred to initiate extradition proceedings for the return of the person;
d) the person transferred shall receive credit for service of the sentence being served in the State from which the person was transferred for time spent in the custody of the State to which the person was transferred.
3. Unless the State Party from which a person is to be transferred in accordance with this article so agrees, that person, whatever that person’s nationality, shall not be prosecuted or detained or subjected to any other restriction of personal liberty in the territory of the State to which that person is transferred in respect of acts or convictions anterior to that person’s departure from the territory of the State from which such person was transferred.