It is widely accepted that most international commercial arbitration cases turn on issues of fact; and questions of fact depend upon the evidential material adduced before the arbitral tribunal. And yet, the topic of evidence in international arbitration literature is somewhat neglected, let alone the question of which laws apply to the taking and evaluation of evidence.
Traditionally, the taking of evidence has been considered to fall within the realm of procedure, and thus to be subject to the law governing the arbitration.2 This chapter takes a step back to examine whether all evidentiary issues are or should be regarded as procedural and tests the boundaries of the substance-procedure dichotomy. As one commentator has put it:
[M]any evidential issues straddle the divide between substantive and procedural law (such as the parol evidence rule or the standard of proof), falling one side or the other depending on which law provides the classification. This is a particular problem in the field of international arbitration where more than one law or rule of law is applicable to the substantive contract, the continuous or individual arbitration agreement and the arbitration itself.3
Against this backdrop, it has been suggested that evidence has a static and a dynamic aspect: under the former, evidence is decisive or relevant for the certainty of a fact, and thus belongs to the realm of substantive law; under the latter, evidence is aimed at the presentation and verification of facts, and thus is subject to procedural law.4 Having in mind the fluid nature of evidence, this study aims to unpack the substance-procedure distinction and to shed light into those issues that lie in the ‘greyzone’.