Rome Statute of the International Criminal Court 2. 3. (b) The case has been investigated by a State which has jurisdiction over it and the State has decided not to prosecute the person concerned, unless the decision resulted from the unwillingness or inability of the State genuinely to prosecute; (c) The person concerned has already been tried for conduct which is the subject of the complaint, and a trial by the Court is not permitted under article 20, paragraph 3; (d) The case is not of sufficient gravity to justify further action by the Court. In order to determine unwillingness in a particular case, the Court shall consider, having regard to the principles of due process recognized by international law, whether one or more of the following exist, as applicable: (a) The proceedings were or are being undertaken or the national decision was made for the purpose of shielding the person concerned from criminal responsibility for crimes within the jurisdiction of the Court referred to in article 5; (b) There has been an unjustified delay in the proceedings which in the circumstances is inconsistent with an intent to bring the person concerned to justice; (c) The proceedings were not or are not being conducted independently or impartially, and they were or are being conducted in a manner which, in the circumstances, is inconsistent with an intent to bring the person concerned to justice. In order to determine inability in a particular case, the Court shall consider whether, due to a total or substantial collapse or unavailability of its national judicial system, the State is unable to obtain the accused or the necessary evidence and testimony or otherwise unable to carry out its proceedings. Article 18 Preliminary rulings regarding admissibility 1. When a situation has been referred to the Court pursuant to article 13 (a) and the Prosecutor has determined that there would be a reasonable basis to commence an investigation, or the Prosecutor initiates an investigation pursuant to articles 13 (c) and 15, the Prosecutor shall notify all States Parties and those States which, taking into account the information available, would normally exercise jurisdiction over the crimes concerned. The Prosecutor may notify such States on a confidential basis and, where the Prosecutor believes it necessary to protect persons, prevent destruction of evidence or prevent the absconding of persons, may limit the scope of the information provided to States. 2. Within one month of receipt of that notification, a State may inform the Court that it is investigating or has investigated its nationals or others within its jurisdiction with respect to criminal acts which may constitute crimes referred to in article 5 and which relate to the information provided in the notification to States. At the request of that State, the Prosecutor shall defer to the State's investigation of those persons unless the Pre-Trial Chamber, on the application of the Prosecutor, decides to authorize the investigation. 3. The Prosecutor's deferral to a State's investigation shall be open to review by the Prosecutor six months after the date of deferral or at any time when there has been a significant change of circumstances based on the State's unwillingness or inability genuinely to carry out the investigation. 4. The State concerned or the Prosecutor may appeal to the Appeals Chamber against a ruling of the Pre-Trial Chamber, in accordance with article 82. The appeal may be heard on an expedited basis. 5. When the Prosecutor has deferred an investigation in accordance with paragraph 2, the Prosecutor may request that the State concerned periodically inform the Prosecutor of the progress of its investigations and any subsequent prosecutions. States Parties shall respond to such requests without undue delay. 6. Pending a ruling by the Pre-Trial Chamber, or at any time when the Prosecutor has deferred an investigation under this article, the Prosecutor may, on an exceptional basis, seek authority from the Pre-Trial Chamber to pursue necessary investigative steps for the purpose of preserving evidence where there is a unique opportunity to obtain important evidence or there is a significant risk that such evidence may not be subsequently available. 7. A State which has challenged a ruling of the Pre-Trial Chamber under this article may challenge the admissibility of a case under article 19 on the grounds of additional significant facts or significant change of circumstances. 11