When, on 3 May 2011, the Appeals Chamber reversed the decision of Trial Chamber III in the Bemba case that had admitted material on a list of the prosecution into evidence, it addressed various central issues related to the admission of evidence under the legal framework of the International Criminal Court (inter alia, the orality principle). The present article critically analyses both decisions. In particular, it views the Trial Chamber's approach that envisages a multi-tiered process of admitting evidence, in light of the approaches of civil law and common law, and expresses concerns about uncertainties and protraction that may result. As the Court's legal framework does not determine that the processing of evidence follow either the civil-law or the common-law model, this is left for the trial chambers to decide in each case. In determining the preferable approach for each respective case, consideration of the procedural context is key. The Appeals Chamber decision allows for the required leeway of the trial chambers in regulating the processing of evidence, to adopt a way that fits the particular circumstances best.

On 25 September 2009, the Appeals Chamber of the International Criminal Court (ICC) issued a seminal decision on the subject of complementarity in the case Prosecutor v. Germain Katanga. The outcome of the Chamber's decision is that, even if a state has initiated an investigation or prosecution against an individual, the ICC may prosecute that individual for the same crimes or even a more selective range of crimes, so long as the state is willing to close the ongoing investigation or prosecution at the request of the ICC Prosecutor. While this decision is defensible under the language of the Rome Statute, this article concludes that, absent vigilance on the part of the ICC's Office of the Prosecutor, the decision could produce consequences inconsistent with the principle that the ICC is intended to act as a court of last resort. These potential consequences, in turn, suggest that the prosecution's policy of ‘positive complementarity’ – that is, encouraging genuine national proceedings whenever possible – should be at the core of its case selection strategy. At the same time, in those instances when the ICC prosecution determines that, despite activity by a national system with respect to a particular case, it is appropriate for the ICC to take over the case, the prosecution should clearly and publicly explain the factors that led to its decision.

This article analyses the requirements when the ICTY Appeals Chamber may overturn factual findings made by a Trial Chamber and may admit fresh evidence. The conclusion is that the Appeals Chamber should overturn factual findings only when strong reasons so indicate, since trial transcripts cannot provide the same information as did live impressions from the proceedings when the Trial Chamber reached its findings. Fresh evidence should be admitted exceptionally; otherwise the control (corrective) function of the ICTY Appeals Chamber could be weakened, endangering the division of tasks in the court organisation, the effective administration of justice and a final hearing within a reasonable time.