The international criminal courts and tribunals have heard thousands of witnesses in cases of extreme complexity and breadth. Their evidentiary record is overwhelming, with live witness testimony standing out as one of its defining features. Keeping in mind the arguments and policies of judicial efficiency and fairness, this article empirically examines the trends and patterns in viva voce witness numbers at the International Criminal Tribunal for the Former Yugoslavia (ICTY), for Rwanda (ICTR), and the International Criminal Court (ICC). We observe clear differences between institutions and individual cases, and discuss the underlying reasons for such divergences. As well as providing a general overview, we demonstrate the complex interaction between case-related characteristics, institutional and situational contexts, and the number of witnesses called at trial.

This article introduces some quantitative and qualitative analysis on the use of written witness statements in lieu of oral testimony at trial to assess in practice the impact of the rules on the admissibility of written witness testimony before the International Criminal Tribunal for the Former Yugoslavia, the International Criminal Tribunal for Rwanda, and the Special Court for Sierra Leone. It traces pieces of evidence admitted under the newer, more liberal, rules on written witness testimony from admissibility to judgment, to establish what impact, if any, these rules have had in practice and whether the critique that such rules might jeopardize fair-trial standards has been realized. The analysis illustrates that the newer rules on admissibility are used with relative infrequency in some tribunals, but that the admission of such statements could raise the question of equality of arms in others, given that the more liberal rules on written statements tend to be used more frequently by the prosecution than by the defence. It will be shown that some chambers have continued to emphasize the importance of oral testimony and have taken a very cautious approach when weighing written testimony, whilst others have suggested that written testimony that was not subject to full cross-examination should not, in principle, be given less weight than oral testimony. The ‘totality of the evidence’ approach in weighing the evidence will be analysed from a practical standpoint, and it will be shown that recent Appeals Chamber jurisprudence suggests that trial chambers may need to take a more particularized approach to pieces of evidence in the future.

The Nicaragua case demonstrates the Court's competence in receiving and interpreting evidence, and in making reasoned findings of fact, even in the most complicated evidentiary context, as is often presented in cases involving use of force and armed conflict. The Court applied well-established standards for evaluating the conflicting evidence presented to it. In particular, the Court determined that greater weight should be given to statements against interest made by high-level government officials than to a state's self-serving declarations. The Court also determined that statements by disinterested witnesses with first-hand knowledge should receive greater weight than mere statements of opinion or press reports. In applying these guidelines, the Court found, correctly, that (i) the United States had used military and paramilitary force against Nicaragua both directly and indirectly, by organizing, financing, arming, and training the Contra guerrillas to attack Nicaragua; (ii) the evidence did not support a finding that the United States exercised direct control over the Contras’ day-to-day operations; and (iii) there was no evidence that Nicaragua supplied arms to guerrillas fighting against the government of El Salvador during the relevant period, or carried out an armed attack against that state. While Judge Schwebel's dissent criticized the last of these findings, in fact, the evidence fully supported the Court's conclusion. In subsequent decisions during the past 25 years, the Court has continued to rely on the approach to evidence first elaborated in the Nicaragua case and has continued to demonstrate its competence as a finder of fact, including in cases involving armed conflict (Bosnia Genocide) and complex scientific and technical issues (Pulp Mills).

This article is intended to be a report of the oral proceedings in the Application of the Convention on the Prevention and Punishment of the Crime of Genocide (Bosnia and Herzegovina v. Serbia and Montenegro), detailing what took place in the Peace Palace and considering the arguments of the parties relating to the procedure adopted in the proceedings. These include the preliminary question of whether or not the International Court of Justice has jurisdiction in the case, a question which has been reopened by Serbia and Montenegro following the 2004 judgment in the Legality of the Use of Force cases; the question of the impact of the workings of the ICTY on the current proceedings; the issue of new documents which has arisen, given the very long gap between the written and oral proceedings; the burden and standard of proof adopted by the Court and what inferences it may draw; and the methodology for hearing witness testimony in the Court. Each of the parties addressed the Court on these procedural issues in some detail, in addition to their pleadings on the substance of the merits of the case.