In which other cases has oral testimony been given in proceedings at the International Court of Justice and other standing international tribunals dealing with inter-State cases? In particular, in which ICJ or other inter-State case or cases has an expert or witness been subjected to cross-examination by the other party?
Semir Sali correctly pointed out four cases in which witnesses were called and examined at the ICJ. In the Corfu Channel Case – the first contentious case at the ICJ – several Naval officers were called as witnesses and were examined in chief and cross-examined. Also, witnesses were called and examined in the ELSI case (US v. Italy). At the merits phase of the Bosnia Genocide Convention case, both parties called a number of experts and witnesses. In particular, each side called very senior British military officers - General Dannatt and General Sir Michael Rose - to testify. Examination for Serbia was done by Prof Ian Brownlie QC and for Bosnia by Joanna Korner QC
As Semir Sali and Serena Forlati both point out, in the Nicaragua case (Nicaragua v US), Nicaragua called a number of witnesses to testify. However, as the US did not appear at the mertis stage, these individuals were not cross examined. Indeed it was Judge Schwebel that took on the task of probing these withnesses
Witnesses have also been called and examined at the International Tribunal for the Law of the Sea. as with the ICJ this happened in the very first case at ITLOS - the MV Saiga Case (St Vincent v. Guinea)
One interesting feature that unites almost all of these cases is that in all but one of the cases mentioned here, examination and cross examination was carried out mainly by English barristers! The one exception is the ELSI case (US v. Italy) where examination and cross-examination was carried out by American lawyers on both sides (Abraham Sofaer for the US and Keith Highet for Italy).
UPDATE: Caroline Foster, who has done tremendous work on expert evidence in international tribunals, has posted a comment to my original post in which she points out other inter-state cases in which experts have been called as witnesses and cross examined. She refers to a number of inter-State arbitral cases as well cases at ITLOS and the WTO. She also raises interesting questions about how international cases dealing with expertise should be handled.