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. Article 20 Special investigative techniques 1. If permitted by the basic principles of its domestic legal system, each State Party shall, within its possibilities and under the conditions prescribed by its domestic law, take the necessary measures to allow for the appropriate use of controlled delivery and, where it deems appropriate, for the use of other special investigative techniques, such as electronic or other forms of surveillance and undercover operations, by its competent authorities in its territory for the purpose of effectively combating organised crime. 2. For the purpose of investigating the offences covered by this Convention, States Parties are encouraged to conclude, when necessary, appropriate bilateral or multilateral agreements or arrangements for using such special investigative techniques in the context of cooperation at the international level. Such agreements or arrangements shall be concluded and implemented in full compliance with the principle of sovereign equality of States and shall be carried out strictly in accordance with the terms of those agreements or arrangements. 3. In the absence of an agreement or arrangement as set forth in paragraph 2 of this Article, decisions to use such special investigative techniques at the international level shall be made on a case-by-case basis and may, when necessary, take into consideration financial arrangements and understandings with respect to the exercise of jurisdiction by the States Parties concerned. 4. Decisions to use controlled delivery at the international level may, with the consent of the States Parties concerned, include methods such as intercepting and allowing the goods to continue intact or be removed or replaced in whole or in part. Article 21 Transfer of criminal proceedings States Parties shall consider the possibility of transferring to one another proceedings for the prosecution of an offence covered by this Convention in cases where such transfer is considered to be in the interests of the proper administration of justice, in particular in cases where several jurisdictions are involved, with a view to concentrating the prosecution. Article 22 Establishment of criminal record Each State Party may adopt such legislative or other measures as may be necessary to take into consideration, under such terms as and for the purpose that it deems appropriate, any previous conviction in another State of an alleged offender for the purpose of using such information in criminal proceedings relating to an offence covered by this Convention. Article 23 Criminalisation of obstruction of justice Each State Party shall adopt such legislative and other measures as may be necessary to establish as criminal offences, when committed intentionally: (a) the use of physical force, threats or intimidation or the promise, offering or giving of an undue advantage to induce false testimony or to interfere in the giving of testimony or the production of evidence in a proceeding in relation to the commission of offences covered by this Convention; (b) the use of physical force, threats or intimidation to interfere with the exercise of official duties by a justice or law enforcement official in relation to the commission of offences covered by this Convention. Nothing in this subparagraph shall prejudice the right of States Parties to have legislation that protects other categories of public officials. Article 24 Protection of witnesses 1. Each State Party shall take appropriate measures within its means to provide effective protection from potential retaliation or intimidation for witnesses in criminal proceedings who give testimony concerning offences covered by this Convention and, as appropriate, for their relatives and other persons close to them. 2. The measures envisaged in paragraph 1 of this Article may include, inter alia , without prejudice to the rights of the defendant, including the right to due process: (a) establishing procedures for the physical protection of such persons, such as, to the extent necessary and feasible, relocating them and permitting, where appropriate, non-disclosure or limitations on the disclosure of information concerning the identity and whereabouts of such persons; (b) providing evidentiary rules to permit witness testimony to be given in a manner that ensures the safety of the witness, such as permitting testimony to be given through the use of communications technology such as video links or other adequate means. 3. States Parties shall consider entering into agreements or arrangements with other States for the relocation of persons referred to in paragraph 1 of this Article. 4. The provisions of this Article shall also apply to victims in so far as they are witnesses. Article 25 Assistance to and protection of victims 1. Each State Party shall take appropriate measures within its means to provide assistance and protection to victims of offences covered by this Convention, in particular in cases of threat of retaliation or intimidation. 2. Each State Party shall establish appropriate procedures to provide access to compensation and restitution for victims of offences covered by this Convention. 3. Each State Party shall, subject to its domestic law, enable views and concerns of victims to be presented and considered at appropriate