The editorial board of the Leiden Journal of International Law is pleased to announce a debate on a very important but underexposed topic in international criminal law: witness proofing. Witness proofing is an accepted and well-established practice at the International Criminal Tribunal for the former Yugoslavia (ICTY), the International Criminal Tribunal for Rwanda (ICTR), and the Special Court for Sierra Leone (SCSL). It entails setting up a meeting between a party to the proceedings and a witness, usually shortly before the witness is to testify in court, the purpose of which is to prepare and familiarize the witness with courtroom procedure and to review the witness's evidence. Recently a trial chamber of the International Criminal Court (ICC) prohibited witness proofing. On 30 November 2007, Trial Chamber I held in the Lubanga case that the possibility of witness proofing is not expressly provided for in the ICC Statute and its Rules of Procedure and Evidence, and that no general principle exists in national or international criminal law that would require the ICC to adhere to such a practice. Moreover, and this is the most interesting argument, the trial chamber held that the ICC Statute ‘moves away from the procedural regime of the ad hoc tribunals’ and that as a result witness proofing is not easily transferable to the ICC.