WikiLeaks and Beyond: Discerning an International Standard for the Admissibility of Illegally Obtained Evidence

Abstract

There is no clear view in international arbitration law as to whether illegally obtained evidence should be admitted and relied on by tribunals. Because arbitral tribunals do not employ a formal evidentiary filter to exclude all inadmissible evidence from the outset, but rather possess a wide margin of appreciation in weighing and assessing evidence, each decision made on the admissibility of evidence is inevitably fact-driven. This predisposition brings with it a danger that different tribunals will reach strikingly different results on seemingly similar questions. By exploring existing case law it is possible to gain a closer understanding of a common standard on the admission and weighing of illegally obtained evidence. Based on a review of selected prominent cases heard before the International Court of Justice (ICJ), the Court of Justice of the European Union (CJEU), the European Court of Human Rights (ECtHR) and international tribunals established under International Centre for Settlement of Investment Disputes (ICSID) or the United Nations Commission on International Trade Law (UNCITRAL) rules, it can be concluded: First, the fact that evidence is obtained illegally will not automatically disqualify such evidence as inadmissible. Second, while a common test for deciding the admissibility of unlawfully obtained evidence still remains to be defined, at least some common legal and policy elements may be distinguished, and serve as much needed guidance. This article analyses the common elements which are often taken into account when deciding admissibility of illegally obtained evidence. It proposes a three-step approach to evaluating evidence that should assist tribunals to reach decisions which are both justifiable and aligned, to the extent possible, with the reasoning expressed in previous international cases.