On 7 September 2009, the International Co-Prosecutor filed two Introductory Submissions, requesting the Co-Investigating Judges to initiate an investigation concerning five suspected persons. These two submissions are divided into what is known as Case Files 003 and 004.
The International Co-Investigating Judge charged Ao An in Case 004 on 27 March 2015 and expanded the charges on 14 March 2016. On 16 December 2016, the Co-Investigating Judges concluded the judicial investigation against Ao An and the case was severed, creating Case File 004/02. The severance was ordered because the charged person has the right to be informed of the decision on the charges brought against him without undue delay, and in order to issue the Closing Order in a reasonable time according to the Internal Rules 67 and 21(4) whether it be a dismissal order or indictment.
On 16 August 2018, the Co-Investigating Judges issued two separate closing orders in the case against Ao An, due to a disagreement about whether Ao An is subject to the ECCC’s personal jurisdiction as a senior leader or one of the persons most responsible for crimes committed during the period of Democratic Kampuchea.
The National Co-Investigating Judge was of the view that Ao An does not fall under the ECCC’s personal jurisdiction under either category and dismissed the case against Ao An for that reason. The International Co-Investigating Judge was of the view that Ao An is subject to the ECCC’s personal jurisdiction as one of the most responsible persons, and that there is sufficient evidence to indict him for the genocide of the Cham and crimes against humanity, as well as domestic offences under Cambodian law.
The Co-Lawyers for Ao An and National Co-Prosecutor filed appeals against the International Co-Investigating Judge’s Closing Order (Indictment), whereas the International Co-Prosecutor filed an appeal against the National Co-Investigating Judge’s Closing Order (Dismissal). The Pre-Trial Chamber held three days of in camera hearings on the appeals against the closing orders on 19, 20 and 21 June 2019.
On 16 December 2019, the Pre-Trial Chamber filed its considerations on the appeals against the closing orders. It unanimously declared “that the Co-Investigating Judges’ issuance of the Two Conflicting Closing Orders was illegal”. Since the Chamber had “not attained the required majority of four affirmative votes to reach a decision based on common reasoning on the merits”, the judges attached their respective opinions to the unanimous considerations.