Some authors have pointed out the dichotomy that may be made between two types of appointed experts and the dilemma that may arise. In addition to a neutral expert appointed by the arbitrators, there may be expert witnesses who provide technical advice, usually supporting the party that appointed and paid them[1]. This statement highlights two key distinctions in practice: i) Tribunal- or jointly-appointed expert, considered to be an independent or neutral expert; ii) Party-appointed expert, also described as a 'party's agent.'

The perception of being 'neutral' or a 'party's agent' may create tension and raises the issue of potential conflicts of interest. A conflict of interest is defined in a general manner as a situation in which someone’s private interests are opposed to that person's responsibilities to other people. Some authors define this concept in more detailed manner, being a situation in which the professional or institutional mission entrusted to a person conflicts with his or her own interest, so that the independence, impartiality and objectivity of his or her judgment are impaired. Can be described as an objective conflict (family relations, economic relations) or a subjective conflict (friendships, disagreements)[2].

While most arbitration rules used by institutions generally address conflicts of interest for arbitrators (see also the Guidelines on Conflicts of Interest in International Arbitration published by the International Bar Association), there is usually no direct reference to conflict of interest for expert witnesses, nor are there references to principles regarding this. However, some rules do mention principles of independence, impartiality, or objectivity, particularly for tribunal-appointed experts.

I.The Standards Provided by the UNCITRAL’s Instruments

A.The UNCITRAL Model Law on Arbitration

The 2006 UNCITRAL Model Law on Arbitration (the “UNCITRAL Model Law”) does not explicitly distinguish between tribunal-appointed experts and party-appointed expert witnesses in separate sections. Article 26(1) allows the tribunal to appoint one or more experts, while Article 26(2) provides the parties the opportunity to present expert witnesses. This possibility is related to Article 18 of the UNCITRAL Model Law, which ensures that each party is given a full opportunity to present its case^[3].

Based on the provisions of the UNCITRAL Model Law, we can identify two functions for the use of experts: i) to report to the tribunal on specific issues to be determined by the arbitral tribunal; ii) To provide evidence to the tribunal. Nevertheless, the UNCITRAL Model Law does not specify any standards, such as requirements for independence or impartiality.

B.The UNCITRAL Arbitration Rules

The 2010 UNCITRAL Arbitration Rules explicitly differentiate between expert witnesses and tribunal-appointed experts, particularly through Articles 27 and 29.

The presentation of expert witnesses is addressed in the context of evidence production. According to Article 27(2), witnesses, including expert witnesses, presented by the parties to testify before the arbitral tribunal on matters of fact or expertise may be any individual, regardless of whether that individual is a party to the arbitration or connected to a party. Unless the arbitral tribunal directs otherwise, statements by witnesses, including expert witnesses, may be submitted in writing and must be signed by the individual providing the testimony.

Regarding tribunal-appointed experts, Article 29(1) provides that, after consulting with the parties, the arbitral tribunal may appoint one or more independent experts to deliver a written report on specific issues that the tribunal must decide. A copy of the expert's terms of reference, as defined by the arbitral tribunal, must be communicated to the parties. Further, under Article 29(2), the expert is required, in principle, to submit to the arbitral tribunal and the parties a description of his or her qualifications and a declaration of impartiality and independence before accepting the appointment. While the UNCITRAL Arbitration Rules provide a model statement of independence for arbitrators pursuant to Article 11, no such model is provided for experts. Such statement usually declares that there are no circumstances, past or present, likely to give rise to justifiable doubts concerning the arbitrator’s impartiality or independence.

C.UNCITRAL Notes on Organizing Arbitral Proceedings

The issue of independence and impartiality for experts is, to some extent, addressed by the 2016 Notes on Organizing Arbitral Proceedings (the "UNCITRAL Notes"). The UNCITRAL Notes outline various techniques for managing reports by party-appointed experts, such as agreeing on a joint list of issues for the experts to address, or producing a joint report that highlights points of agreement and disagreement (par. 94-95). It is clear that party-appointed experts are instructed by the respective parties on the issues they are to address. However, this does not imply that the arbitral tribunal relinquishes control over how evidence submitted by party-appointed experts is produced (par. 96-100). The UNCITRAL Notes also recognize potential transparency concerns. To address these, they suggest that "the arbitral tribunal may wish to clarify the nature and extent of communication between the parties or their representatives and their experts, and whether a party might be requested to disclose such communications."

For tribunal-appointed experts, the UNCITRAL Notes discuss the expert's role and outline the methods available to the tribunal for structuring the expert’s mandate and relationship with the tribunal (par. 101-107). Two primary functions for such experts are identified: preparing a report on specific issues requiring specialized knowledge, and assisting the arbitral tribunal in understanding certain technical matters. This does not preclude the tribunal from appointing an expert at a later stage in the proceedings, particularly if the evidence provided by party-appointed experts proves inconclusive. In addition to outlining the expert's qualifications, the UNCITRAL Notes emphasize the need for the expert to submit a declaration of impartiality and independence. However, the UNCITRAL Notes specify that this statement is to be obtained by the tribunal (par. 102). The Terms of Reference (the “ToR”) serve as the instrument used to define the scope of the expert's mandate. According to the UNCITRAL Notes, the ToR is also employed "to ensure transparency regarding the relationship between the arbitral tribunal and the tribunal-appointed expert" (par. 106).

II.Selected Guidelines and Practices

A.The Chartered Institute of Arbitrators’ Practice Guidelines

1.Practice Guidelines No. 07 on Party-appointed and Tribunal-appointed Experts

The Chartered Institute of Arbitrators’ Practice Guidelines No. 07 on Party-appointed and Tribunal-appointed Experts (the “CIArb Practice Guidelines”) serves to delineate best practices in international commercial arbitration concerning the appointment and utilization of both party-appointed and tribunal-appointed experts.

Article 3 of the CIArb Practice Guidelines addresses the way expert evidence can be adduced. Notably, the CIArb Practice Guidelines emphases the importance of securing the parties’ agreement on the expert selected by the arbitrators, stating that “it is essential to obtain the parties’ agreement to the expert selected by the arbitrators in order to reduce the risk of later challenges to the expert, their expert report, and/or any award relying on it.” Certain institutional rules may require the tribunal to invite the parties to comment on the choice of any prospective expert. During the expert selection process, the tribunal may also request that the parties provide a list of criteria they believe the tribunal-appointed expert should possess.

The CIArb Practice Guidelines identify three key qualities that tribunal-appointed experts must demonstrate: appropriate qualifications and expertise, availability, and independence and impartiality. Furthermore, the Guidelines stress that the tribunal must manage specific matters relating to the tribunal-appointed expert, such as establishing a communication protocol that governs the interactions between the tribunal, the expert, and the parties.

The CIArb Practice Guidelines highlight the potential risks to independence and impartiality that may arise from private communications or deliberations involving the tribunal-appointed expert. Arbitrators are cautioned against engaging in private discussions or communications with the expert, as this could form the basis for challenges on the grounds of lack of due process, independence, or impartiality. To mitigate these risks, the CIArb Practice Guidelines recommend that all communications between the arbitrators and the expert be conducted transparently, with copies of correspondence provided to all parties, and that any discussions with the expert take place in the presence of the parties. This is particularly important when the expert is appointed by the tribunal, as the risk of challenges is heightened in such cases.

In the context of party-appointed experts, the CIArb Practice Guidelines recognize the interaction between the appointing party and its expert. According to the commentary on Article 4, the party appointing the expert is responsible for directing the expert’s assignment and ensuring that the expert adheres to any instructions provided by the arbitrators regarding the exchange of views or meetings with the opposing party’s expert. These instructions may include directions for the experts to meet to narrow differences of opinion and to produce a joint report outlining points of agreement and disagreement, along with explanations for the discrepancies.

However, the CIArb Practice Guidelines make it clear that, despite being appointed by a party, the expert’s primary duty is to the tribunal rather than to the appointing party. As the CIArb Practice Guidelines state: “The experts should be instructed by the parties that their overriding duty is owed to the tribunal and not to the instructing party.”

2.CIArb Protocol for the Use of Party-Appointed Expert Witnesses in International Arbitration

The Guidelines are supplemented by the CIArb Protocol for the Use of Party-Appointed Expert Witnesses in International Arbitration (the “CIArb Protocol”).

A notable principle outlined in the Preamble of the Protocol is particularly relevant to our discussion: it affirms that “experts should provide assistance to the Arbitral Tribunal and not advocate for the position of the party appointing them.” This principle underscores the expert’s duty to the tribunal, reinforcing the expert’s role as neutral contributor rather than partisan advocate.

Moreover, the Protocol emphasizes that these principles[4] should, to the greatest extent possible, be established before any evidentiary hearing, with the aim of achieving maximum agreement between the experts involved. 

Article 4 of the CIArb Protocol for the Use of Party-Appointed Expert Witnesses in International Arbitration addresses the independence and duty of a party-appointed expert, as well as the essential components to be included in a written expert opinion.

The article highlights three primary conditions related to the expert’s independence: 1) An expert's opinion must be impartial and objective; 2) The payment of reasonable professional fees by the appointing party does not compromise the expert's impartiality; 3) The expert's primary duty is to assist the Arbitral Tribunal in resolving the issues for which expert evidence is provided.

In addition, Article 4 specifies the necessary content of an expert opinion. Besides procedural details, the critical elements for assessing independence and impartiality include:

• A statement disclosing any past or present relationship with any of the parties, the Arbitral Tribunal, counsel or other representatives, other witnesses, or any other person or entity involved in the arbitration.
• A statement outlining all instructions received from the appointing party, the basis of the expert's remuneration, and a declaration as provided in Article 8 of the Protocol.

Article 8 of the CIArb Protocol for the Use of Party-Appointed Expert Witnesses in International Arbitration provides a sample declaration for experts, translating such principles and underscoring their obligation to maintain independence and impartiality when producing evidence. In this declaration, the expert affirms that their primary duty is to assist the arbitral tribunal in resolving the issues for which expert evidence is presented, and the expert pledges to adhere to this responsibility throughout the arbitration process. The expert explicitly confirms that his opinion is impartial and objective, acknowledging his duty to bring to the tribunal's attention any matters that could potentially affect his opinion. Furthermore, the expert commits to promptly notifying the parties and the tribunal of any necessary corrections or modifications to the opinion as the arbitration progresses.

The Protocol reinforces the arbitral tribunal's authority to determine the admissibility, relevance, materiality, and weight of the evidence, in line with Article 27(4) of the UNCITRAL Arbitration Rules. Failure to meet the standards set out in the expert's declaration may result in the arbitral tribunal disregarding the expert's written opinion and testimony, either wholly or in part, as deemed appropriate under the given circumstances.

This framework ensures the integrity of expert evidence by aligning the expert's role with the tribunal's evaluative functions, thereby safeguarding the fairness and transparency of the arbitration process.

B.Selected arbitration rules

1.The 2021 ICC Arbitration Rules

The International Chamber of Commerce (the “ICC”) Arbitration Rules 2021 address the issue of experts under the provisions related to Establishing the Facts of the Case (Article 25). According to these rules, the arbitral tribunal may decide to hear experts appointed by the parties (Article 25.2). Additionally, after consulting with the parties, the tribunal may appoint one or more experts, define their terms of reference, and receive their reports. Upon a party’s request, the tribunal is obligated to provide the parties with an opportunity to question the expert during a hearing (Article 25.3).

The Rules for Expertise of the ICC, in force since 1 January 2003, further detail the framework for the appointment and conduct of experts. These rules allow the arbitral tribunal to outsource an expert. As a general matter, it is provided that before being proposed as an expert, a prospective candidate must sign a declaration of independence and disclose in writing any facts or circumstances that could raise doubts regarding their independence in the eyes of the party requesting the proposal. This information must be communicated to the party by the Centre, which will also set a deadline for any comments or objections (Article 3, (3)). It is explicitly required that every expert must remain independent of the parties involved in the proceedings, unless all parties have agreed otherwise in writing (Section III, Article 7, (3)).

IBA Rules on the Taking of Evidence in International Arbitration are generally used to complete the ICC Rules art. 25 (3)[5]. It is also relevant to note that the CIARB Practice guidelines and its Protocol are drafted in line the IBA Rules.

2.LCIA Arbitration Rules 2020

For tribunal-appointed experts, Article 21.2 stipulates that any such expert must remain impartial and independent of the parties throughout the proceedings. The expert is required to sign a written declaration confirming their impartiality and independence, which is submitted to the arbitral tribunal and shared with all parties involved.

Regarding witnesses in general, Article 20.8 provides the possibility for the arbitral tribunal to administer an oath or affirmation to a witness. Further guidance on the role of tribunal-appointed experts is provided in Paragraph 280 of the LCIA Guidance Note for Parties and Arbitrators. It emphasizes the expert's duty to remain impartial and independent. The arbitral tribunal is encouraged to request the expert to formally confirm their independence and impartiality by completing a statement to that effect. Before finalizing the expert’s appointment, the tribunal should also confirm the expert’s scope of work and engagement terms. Once the expert's statement of independence and impartiality is completed, it should be communicated to all parties to ensure transparency and maintain trust in the arbitration process

VTA’s Model Arbitration Clause: “Mọi tranh chấp phát sinh từ hoặc liên quan đến hợp đồng này sẽ được giải quyết bằng trọng tài tại Trung tâm Trọng tài Thương nhân Việt Nam (VTA) theo Quy tắc tố tụng trọng tài của Trung tâm này”. “Any dispute arising out of or in relation with this contract shall be resolved by arbitration at the Vietnam Traders Arbitration Centre (VTA) in accordance with its Rules of Arbitration”.

The Vietnam Trade Arbitration Center (VTA) is responsible for organizing and coordinating the resolution of business disputes through institutional arbitration, with jurisdiction over disputes including: (i) disputes arising from commercial activities between parties; (ii) disputes involving at least one party engaged in commercial activities; and (iii) disputes as prescribed by law to be resolved by arbitration.