Subject matter experts are regularly used in complex cases before national courts. Across jurisdictions, their role is usually the same: to provide a professional opinion on the basis of their specialized training or experience on a matter of relevance to the dispute. Significant variation exists, however, in the relationship of the experts with the litigants. In civil law countries, local procedural rules typically require courts to appoint experts directly, and to closely supervise any interaction with the parties. In stark contrast, litigants in common law jurisdictions are normally allowed to select, engage, remunerate and privately communicate with ‘their’ experts.
The complex and multi-faceted nature of investment disputes means that experts are also relied upon heavily in treaty arbitration proceedings. They are regularly employed to assist tribunals with legal, technical and valuation matters. Like many other procedural aspects of international arbitration, the manner in which expert evidence is provided depends, to a great extent, on the agreement of the parties. An examination of case law demonstrates that both common and civil law-inspired approaches have been adopted. There are instances where only one tribunal-appointed expert has been used; although, in most proceedings, experts are separately appointed by each side.