The evidentiary rules that apply in international commercial arbitration tend to blend elements from both common law and civil law traditions, creating a flexible and pragmatic approach tailored to the needs of the specific dispute. However, they are generally more akin to the principles found in civil law systems rather than common law systems. Here’s why:

Unlike strict procedural codes found in common law systems (e.g., the Federal Rules of Evidence in the U.S.), international commercial arbitration offers significant flexibility. The parties can agree on the procedural rules, including evidentiary matters, which might combine practices from both legal traditions.

Arbitrators in international commercial arbitration often take a more active role in determining the admissibility and weight of evidence, similar to judges in civil law systems. They have broad discretion to manage evidence, unlike in common law systems, where evidentiary rules are more rigid, and the parties play a dominant role in presenting evidence.

The general approach in international arbitration focuses on the relevance and materiality of evidence rather than strict rules on admissibility. This mirrors the civil law system’s preference for substance over form. In common law systems, rules of evidence tend to be more formal and exclusionary.

International arbitration often emphasizes documentary evidence over oral testimony, aligning more closely with civil law practices. Discovery procedures, especially extensive pre-trial discovery common in common law jurisdictions, are generally limited. The International Bar Association (IBA) Rules on the Taking of Evidence in International Arbitration provide a compromise, offering guidelines that blend both traditions but with a tendency towards the more limited, focused disclosure seen in civil law.

While cross-examination, a hallmark of common law proceedings, is used in international arbitration, it is usually more controlled and limited. The process is less adversarial compared to common law trials, reflecting civil law influences where the judge (or arbitrator) controls the questioning.

Expert evidence in international arbitration may be handled similarly to civil law systems, where experts are appointed by the tribunal rather than the parties. This contrasts with the common law approach where parties often engage their own experts to support their case.

Overall, the evidentiary rules in international commercial arbitration are more aligned with civil law traditions due to their flexibility, the active role of arbitrators, and the focus on the relevance of evidence over formalistic rules. However, the practice also incorporates certain common law features, such as the use of cross-examination and the possibility for parties to engage their own experts. This hybrid approach is designed to accommodate parties from diverse legal backgrounds and ensure fair and efficient resolution of disputes.