of his or her personal liberty in that territory in respect of acts, omissions or convictions prior to his or her departure from the territory of the requested State Party. Such safe conduct shall cease when the witness, expert or other person having had, for a period of fifteen consecutive days or for any period agreed upon by the States Parties from the date on which he or she has been officially informed that his or her presence is no longer required by the judicial authorities, an opportunity of leaving, has nevertheless remained voluntarily in the territory of the requesting State Party or, having left it, has returned of his or her own free will. 28. The ordinary costs of executing a request shall be borne by the requested State Party, unless otherwise agreed by the States Parties concerned. If expenses of a substantial or extraordinary nature are or will be required to fulfil the request, the States Parties shall consult to determine the terms and conditions under which the request will be executed, as well as the manner in which the costs shall be borne. 29. The requested State Party: (a) Shall provide to the requesting State Party copies of government records, documents or information in its possession that under its domestic law are available to the general public; (b) May, at its discretion, provide to the requesting State Party in whole, in part or subject to such conditions as it deems appropriate, copies of any government records, documents or information in its possession that under its domestic law are not available to the general public. 30. States Parties shall consider, as may be necessary, the possibility of concluding bilateral or multilateral agreements or arrangements that would serve the purposes of, give practical effect to or enhance the provisions of this article. Article 19. Joint investigations States Parties shall consider concluding bilateral or multilateral agreements or arrangements whereby, in relation to matters that are the subject of investigations, prosecutions or judicial proceedings in one or more States, the competent authorities concerned may establish joint investigative bodies. In the absence of such agreements or arrangements, joint investigations may be undertaken by agreement on a case-by-case basis. The States Parties involved shall ensure that the sovereignty of the State Party in whose territory such investigation is to take place is fully respected. 25