A few weeks ago, in the Nuon et al. case, the Co-Investigating Judges of the ECCC formally warned the Defence counsel that they are prohibited from conducting their own investigations and that any breach of the prohibition may result in the application of sanctions against them.
Indeed, unlike the ad hoc Tribunals, the investigation in the ECCC is conducted by the two independent Co-Investigating Judges and not by the parties. It was emphasized in the Order that “there is no provision which authorizes the parties to accomplish investigative action in place of the Co-Investigating Judges, as may be the case in other procedural systems.”
The Co-Investigating Judges noted that it "is apparent that the Defence seeks to base their investigation communication on their repudiation of the civil law process wherein the judicial investigation is conducted solely by the investigating judge".
Indeed, the format of the preliminary investigation affects the format of the trial. Where the parties do not conduct their own investigations, they have no case to present. There is no case for the Prosecution and no case for the Defence in the ECCC. Under the Internal Rules of the ECCC, it is the Chamber that controls the presentation of evidence. For instance, pursuant to Rule 91, the Chamber shall hear the witnesses and experts in the order it considers useful. The Co-Prosecutors and the Defence “shall be allowed to ask questions with the permission of the President.”