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    Expert Insights

The Use of Experts in International Arbitration


Proving your case may require relying on the evidence of experts to give their professional opinion on technical issues. The use of experts in disputes is longstanding, both in courts and arbitration, with records from an Admiralty case heard in England in 1345 showing reliance on an expert to determine if a wound was fresh. Historic court cases aside, expert evidence in arbitration (both domestic and international) is ubiquitous.

International arbitration generally recognises two sorts of experts, namely those appointed by the parties (a practice drawn from the common law), and those appointed by the tribunal (a practice drawn from the civil law).

Party-appointed experts are found in arbitration far more often than tribunal-appointed ones, whose appointments are limited to cases where the tribunal considers it would benefit from expert evidence but the parties have failed to appoint their own experts, or (even more rarely) where the parties have appointed experts but the tribunal believes it needs its own expert to assist with its consideration of the evidence of the party-appointed experts.

In this article we will focus on party-appointed experts, how they are chosen and give their evidence, and what the future may hold for them.

The need for experts

Experts differ from advocates and witnesses in that they can give their opinion on the matters on which they are instructed, usually in the form of a report and then by answers to questions posed by the parties at the final hearing. Insofar as their answers are arguments, they are submissions confined only to certain areas.

A benefit of arbitration is that the tribunal can consist of specialists in a field pertinent to the dispute. However, rarely if ever is an arbitrator an expert in every material field, including on the substantive dispute, foreign laws, and the calculation of damages. Certain professions act as experts in international arbitration more than others, including construction professionals (different types of engineers and surveyors), foreign lawyers, and accountants (as experts on quantum). 

Selection and appointment

Under most arbitral rules the tribunal has control of the procedure and whether the parties can call expert evidence, keeping in mind the importance of maintaining a fair procedure that gives each party an adequate chance to present its case. The result is that the rights of parties to appoint experts arises in the procedural order, either agreed between the parties and the tribunal on specific issues of fact, or law or following an application by one of the parties to the tribunal.

Some arbitration rules expressly permit the use of experts. Article 25 of the ICC Rules 2021 permits the tribunal to establish the facts of the case by all appropriate means, and allows the tribunal to hear experts appointed by the parties or by the tribunal itself. Articles 20 and 21 of the LCIA Rules 2020 contain detailed rules on experts too.

A party may have already spoken with a potential expert when identifying the scope of issues on which expert evidence is to be given; more often, the parties agree general areas for expert evidence, and then each search for an expert. Potential experts can be found from online databases of experts, some managed for commercial purposes, and from guides that rank experts in their fields.

Care should be taken to select an expert without any conflict or bias, and who has had experience in giving evidence and being cross-examined before a Tribunal.

Neutrality of party-appointed experts

A problem with the common-law approach to experts is that they can be seen as ‘hired guns’ instructed to fight a party’s case. They are directly hired and paid for by the party, and the expert’s neutrality is thus, to an extent, a fiction.

Various aspects of the expert evidence process can counter this:

  • Transparency, for instance in the qualifications of the expert, in their instructions and the format, substance and then exchange of reports, and the production of a single joint report following a meeting with the opponent’s expert.
  • Cross-examination by the opponent and tribunal, including ‘hot tubbing’ (discussed further below).
  • The procedural laws of the seat of the arbitration and the arbitral rules may give details on neutrality requirements.
  • Professional rules and guidance such as the Chartered Institute of Arbitrators Protocol for the Use of Party-Appointed Expert Witnesses in International Arbitration, Article 4 of which stresses that “An expert’s opinion shall be impartial, objective, unbiased and uninfluenced by the pressures of the dispute resolution process or by any Party… An expert’s duty, in giving evidence in the Arbitration, is to assist the Arbitral Tribunal to decide the issues in respect of which expert evidence is adduced.” Other guidelines include the IBA Rules on the Taking of Evidence in International Arbitration 2020 (Articles 5 and 6), UNCITRAL Notes on Organising Arbitral Proceedings 2016 (paragraphs 92 to 107), and the ICC Techniques for Controlling Time and Costs in Arbitration 2012 (paragraphs 62 to 68).

Exchange of expert evidence

Once the scope of expert evidence is contained in a procedural order, parties generally have a window of time to find and instruct an expert. This can take time, as conflict checks need to be conducted, fees agreed and instructions sent. The expert then needs time to assess the available information, ask for clarifications if necessary, and draft their report by the deadline stipulated in the order.

Expert evidence can initially be given either simultaneously, where the parties swap their reports at the same time, or consecutively, e.g. the claimant serves their report first, following which the respondent has a period of time to file a response.

The experts may then meet to discuss their reports and/or produce a joint report in which they identify and explain areas of agreement and disagreement. The adversarial and joint reports are included in the bundle for the evidentiary hearing, at which the experts may give evidence and be cross-examined individually or together (so-called ‘hot tubbing’ or witness conferencing).

With the parties’ input, the tribunal may give standard directions on the use of expert evidence in the arbitration, with more detailed specific directions in cases of witness conferencing.

Single joint experts and joint reports

Although rare, there are benefits to the parties instructing a single joint expert to deal with the issues. A single expert will be cheaper, and will not need to spend time interacting with any other experts. Once the single joint expert produces a report, all of the parties know the full extent of the expert evidence and can rely on it (in the absence of its own expert, the tribunal’s questions of the single joint expert will be narrow).

If appointed, the single joint expert will only engage with the parties and tribunals in ‘open’ communications, meaning there is no scope for communication hidden from the other party or the tribunal (in English law and procedure, there can be Without Prejudice or Without Prejudice Save As To Costs communication with a single joint expert).

However there are challenges which mean single-joint experts are rarely used. The parties may negotiate fruitlessly over the identity of the single joint expert, given their conflicting interests in what the expert may say. It is also difficult to counter the single joint expert’s evidence as there is no right to serve adversarial evidence contradicting or disagreeing with the joint expert, who may simply be wrong in their conclusions. This usually means the party whose case the expert does not support will seek to instruct their own expert, resulting in a lengthier and more expensive process.

‘Hot tubbing’

Traditionally experts would give evidence separately as one of the various witnesses that a party calls whilst it presents its case. Not, only would this mean that the respondent’s expert might be heard days or weeks after the claimant’s expert, making it difficult to do a direct comparison in respect of their answers on the issues, but cross-examination can often blur the issues or create confusion in the mind(s) of the tribunal. Further, experts may be seen as partisan, or biased, or the evidence may appear too technical and not properly establish the information or context that a tribunal is looking for.

To counter this, it is not uncommon for the tribunal to order at some point towards the end of the final hearing that the two experts be questioned at the same time, thereby generating a discussion on the technical issues. This is formally called ‘witness conferencing’, or more informally as ‘hot-tubbing’. ‘Hot tubbing’ as a concept is widely accepted to have originated in Australia in the 1970s but has become more prevalent since then. It is more commonly used in some countries over others in both litigation and arbitration and many practitioners consider ‘hot tubbing’ to provide a more satisfactory expert witness experience.

As with the joint expert report, areas of agreement can arise quickly during such a discussion, and differing views can be analysed point-by-point. Expert evidence lends itself to witness conferencing much more than evidence of fact because experts give evidence based on their professional opinions and experience, and reasonable experts can disagree on the same point.

It is not without its problems, however. A party considering ‘hot tubbing’ will want to ensure it has a good expert. Experts differ in their comfort around peers who may disagree strongly with their professional judgment. Practically, some people will speak more loudly and with more force than others; debate between experts can descend into detail too fine for the matters in dispute, or otherwise become irrelevant. Many of these concerns can be addressed by the parties and tribunal via strict ground rules on speaking; these should be contained in specific directions.

The future of experts and expert evidence in international arbitration

As shown above with the development of witness conferencing, the way experts give evidence has changed over the years, but what does the future hold?

In 2018, the LCIA produced a Note on Experts in International Arbitration that indicated future directions of travel. One point that was highlighted was that experts are increasingly used to determine disputes (so-called expert determination) rather than just giving evidence, especially in cases where the subject matter of the dispute is more technical than legal. They are also found increasingly as tribunal members and in fact-finding roles. Some experts cross-qualify as lawyers and appear as counsel.

Another trend is that as experts become more focused on specific professional areas, their evidence will probably become increasingly fragmented as disputes turn on ever finer technical points. In high-value and complicated disputes, teams of experts may become necessary to address each of the specialist issues.

These factors will impose costs pressures on parties. Unless controls are imposed on costs, for instance in the form of mandatory cost budgeting, parties may be tempted to use experts who are less well-recognised and therefore cheaper. Computer technology including artificial intelligence may drive down costs as they have done in document collection and disclosure.

However the formal uses of expert evidence may change, what is for certain is that the pivotal role of experts in helping parties prove their claims will remain.

Our expertise

With offices in many of the world’s major arbitration centres, including London, Paris, Geneva, Dubai, Hong Kong and Singapore, we are ideally placed to work with you both to prevent and to resolve disputes as they arise, whatever the law, language, rules, industry sector, or subject matter of that dispute may be. Our dedicated multicultural and multilingual specialists conduct arbitrations under both civil and common law systems and regularly act in arbitration-related domestic court proceedings.

Whether you are a state, a state-owned entity, a sovereign wealth fund, a corporate, a sports federation or authority, private business or individual, our strategically focused specialists will work alongside you through every aspect of any arbitration. Please contact Thomas Snider or your usual Charles Russell Speechly LLP contact if you would like to get in touch. 

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