I. INTRODUCTION

Are expert witnesses the éminences grises of modern international arbitration proceedings?

Questions of increasing technical, scientific, or forensic complexity abound in international arbitration disputes. Arbitral tribunals, if they are to discharge their duty to render fair, reasoned, and enforceable awards, need the assistance of experts in the fields concerned. Assistance derived from expert testimony presupposes that the arbitral tribunal makes its own critical, informed and independent assessment of expert evidence. That much is uncontroversial.

Matters start to blur, however, in those instances where the complexity of technical issues requires more than expert assistance, and where that assistance crosses a threshold and becomes reliance on expert opinion by the arbitral tribunal. What impact does reliance on expert opinion have on the tribunal’s independent assessment of expert evidence, and its decision-making process?

Reliance on expert testimony is an acknowledged phenomenon, described by Judges Al-Khasawneh and Simma of the International Court of Justice as unavoidable in certain highly complex cases: “reliance on experts is all the more unavoidable in cases concerned with highly complex scientific and technological facts. (…) [T]echnical evolution has brought to surface the tension that inevitably exists between the legal conception of ‘fact’ and of evidence on the one hand, and the conception of facts in the sciences, on the other.”1 (Emphasis added)