One of the fundamental differences between arbitration and state court proceedings is the significantly less formal nature of the former. This principle also applies to evidentiary proceedings, where the primary source of the rules governing their conduct is the parties’ agreement, particularly the arbitration clause. The parties may later agree on specific rules for evidentiary proceedings.

Regardless, the parties’ freedom in this regard is substantial, and the following possibilities can be noted:

• In institutional arbitration, the parties may decide to apply the rules of one of the permanent arbitration courts – then the rules on evidence contained therein will apply (such as those provided for, for example, in the Rules of the Court of Arbitration at the Polish Chamber of Commerce of January 1, 2025);
  In ad hoc arbitration, the so-called UNCITRAL Rules apply as a rule;
  The parties may establish the rules (they have almost complete freedom in this respect) according to which evidence will be taken in the proceedings.
  The parties may refer in the agreement to generally applicable provisions (e.g., the provisions of the Code of Civil Procedure, which rarely occurs) or to guidelines on the taking of evidence in arbitration proceedings, which international institutions have adopted.[1]
  
  
  [1]IBA Rules on the Taking of Evidence in International Arbitration Adopted by a resolution of the IBA Council 17 December 2020 International Bar Association.

It is also worth noting that, unlike in proceedings before a state court, in arbitration, there is generally no established hierarchy of evidence or rules according to which the arbitral tribunal should assess its credibility – the arbitrators determine this.

Examples of evidence in arbitration

The most frequently distinguished and practically used evidence in arbitration includes, among others:

1. documentary evidence,
2. evidence from witness statements (in principle, parties to arbitration are also considered “witnesses”),
3. evidence from expert opinion.

1. Documentary evidence

Documentary evidence plays the most important role in most arbitration proceedings. The party and its representative’s main task is to collect and present relevant evidence that justifies the facts cited by the party. Quite often, preparing and collecting evidence requires more time and effort than the actual arbitration proceedings.

In practice, it may occur (and often does) that a party lacks access to all the necessary documents to prove specific facts. In these situations, it might be essential to file a motion for the other party or third parties to produce documents. If there are difficulties in obtaining documents, the arbitration tribunal may request legal assistance from the state court (if such support is available in the given jurisdiction). This process is commonly referred to as securing evidence through the state court.

• Evidence from witness statements

Witnesses in arbitration often play a key role in the case’s outcome. Unlike state court proceedings, arbitration proceedings generally have no rules regarding who may be a witness or how the hearing should be conducted.

It is common for witnesses to give evidence in two stages: first, they give a written statement, and then, if the arbitral tribunal finds it justified, they are heard orally.

It should be remembered that the party is responsible for ensuring that the witness appears at the hearing and is prepared for it. Failure to comply with these obligations may result in negative consequences, such as the refusal to admit this evidence at a later stage (if the witness does not appear on the day of his examination) or even the loss of the case if the information held by the witness was crucial to its examination.

• Evidence from expert opinion

Depending on the type and nature of the case and the merits of the dispute, evidence from expert opinions can be gathered. In this situation, it is important to address factors such as the expert’s availability, area of expertise, and experience in advance to ensure the case is considered efficiently and promptly.

In arbitration, each party selects its own expert. It is a rule. Once the opinions are presented, it is customary to confront both experts and question them during a hearing. Like in the case of witnesses, the responsible party typically ensures the expert’s presence and covers their costs, which the other party may fully reimburse if they win the dispute.

Summary

Given the significant role of the principle of the parties’ autonomy in arbitration, it is important to carefully consider the evidentiary proceedings during the drafting phase of the arbitration clause. There is a wide variety of arbitration institutions, each operating under its own rules, often with differing provisions regarding evidentiary matters. Therefore, it is not necessary to detail evidence issues extensively in the arbitration agreement; instead, it is sufficient to utilize the options already available. This approach also ensures certainty for the parties when interpreting the rules governing evidentiary proceedings.

In summary, the evidence procedure in arbitration can differ significantly from that conducted in state courts. Over the years, the rules have been developed through practice and are generally accepted. Therefore, it is important to possess the necessary knowledge and experience in this area to avoid risking the loss of the case.

Literature:

Włodyka S., Szumański A. (red.), System Prawa Handlowego. Tom 8. Arbitraż Handlowy, Warszawa 2015.

---

[1] IBA Rules on the Taking of Evidence in International Arbitration Adopted by a resolution of the IBA Council 17 December 2020 International Bar Association.