The opportunity to confront and contradict testimony and other evidence is a fundamental tenet of litigation in virtually every legal system: It is accepted that evidence presented by one party cannot be received unless the other party is afforded the opportunity to respond to it. One form of evidence is oral testimony, and one of the most important ways in which this evidence can be challenged is through cross-examination of the witnesses presenting it.

But oral testimony is accorded differing values by various legal systems and, as a result, the extent to which cross-examination is accepted and appreciated in international arbitration, where procedures derive from those systems, frequently varies depending on the backgrounds and training of the persons participating in it. Thus, since legal systems vary considerably in the ways in which they permit the parties to obtain and present evidence, international arbitration proceedings do also, depending on the procedural approach that the parties have agreed on or that the arbitrators impose.

The most important differences in procedure are between those of civil law and common law countries and, in particular, the ways in which they deal with oral presentations by witnesses. Civil law countries, as many American lawyers learned in complying with the procedures of the Iran-United States Claims Tribunal, deal with evidence on the basis of a distrust of the value of oral testimony. As a result, civil law procedure does not generally permit parties (including high ranking officers of a corporate party) to be treated as witnesses—as opposed to presenters of their or their companies' position in the case—and placed under oath or the equivalent. In addition, in civil law systems witnesses are often not permitted to discuss their testimony in advance of their giving it and may be questioned initially at the hearing by the tribunal rather than by the parties' representatives.

The distrust of oral testimony in civil law proceedings is also shown in the ways in which such testimony in the proceedings is preserved. It is unusual for a stenographic record to be kept of the words used by the witnesses or the persons who question them; rather, the presiding officer summarizes the witness's testimony in writing that the witness, after review and comment by the parties’ lawyers, signs, creating another in the series of documents that the parties present over time to make up the record of the case.

There is less emphasis, therefore, on the “showdown” hearing or trial of Anglo-American procedure, which is the only phase in which witnesses may have evidence adduced from them: In Anglo-American procedure, material of an evidentiary nature that is produced or exchanged prior to the trial is preliminary and preparatory and is not part of the record of the case.