12. Expert Witness

Introduction. An expert witness is a specialist engaged by either a party or the arbitral tribunal to provide independent, professional opinions on technical or complex issues that fall outside ordinary knowledge and that a lay fact witness cannot address. In arbitration, expert evidence may be presented by the parties, or the arbitral tribunal may retain its own expert when additional neutral assistance is required.

Arbitrator expertise when considering expert evidence. Although the arbitral tribunal must decide the case based on the evidence presented by the parties, an arbitrator with technical or industry experience may draw on that background to understand the issues, evaluate expert reports, and ask informed questions. This is one reason why the selection of an arbitrator can be strategically important. However, there are clear limits to how an arbitrator may rely on personal expertise. The arbitral tribunal cannot introduce new technical conclusions, methodologies, or factual assumptions that were not put into evidence. Doing so would undermine procedural fairness by depriving the parties of the opportunity to address and challenge the material relied upon. When the arbitral tribunal appoints its own expert, appropriate protocols must be established to ensure transparency and fairness.

Nature of the expert evidence. A well‑qualified expert witness can clarify complex concepts, explain industry standards, and provide analytical frameworks that assist the arbitral tribunal in reaching a reasoned decision. Arbitrators expect experts to provide objective, independent analysis rather than advocacy. Any perception of bias can significantly diminish the weight given to the expert’s evidence. Where the arbitral tribunal has concerns about the objectivity of the parties’ experts, it may appoint its own expert to balance the record. This differs from court proceedings, where expert evidence is almost always left to the parties. An arbitral tribunal‑appointed expert may work alongside party‑appointed experts and will be scrutinized in the same manner as any other expert witness. Although an expert witness may be an employee of a party, this is sometimes viewed as problematic because it may raise questions about independence. Where no technical issues arise, expert evidence is unnecessary.

Multiple rounds of expert reports. The arbitral tribunal must also determine the number of rounds of expert reports and the sequence in which they will be exchanged. The parties will generally voice their views at the case management conference.

Strategic considerations when selecting the expert witness. For in‑house counsel, selecting the right expert is a critical strategic decision. The most persuasive expert is not necessarily the one with the most impressive credentials, but the one who understands the commercial context, communicates clearly and effectively, and can withstand rigorous cross‑examination. This is one of the most important decisions to be made by a case team.

Key considerations

1. When should a party decide whether expert evidence is necessary?

A party should assess the need for expert evidence early on in the dispute, ideally when defining the issues, to determine whether technical, financial, or industry‑specific matters require specialized knowledge. Retainers should be put in place early on to secure the best possible expert evidence.
2. What makes an expert witness strategically valuable?

An expert is valuable when they combine technical competence with the ability to explain complex concepts clearly, situate them in the commercial context, and withstand rigorous cross‑examination. By explaining complicated concepts to an arbitral tribunal, they assist with the adjudication.
3. How important is independence in selecting an expert?

Independence is critical as it goes to the weight that can be given to the evidence. Arbitrators give little weight to experts who appear biased or overly aligned with a party’s narrative, regardless of their credentials and experience.
4. Can an employee of a party serve as an expert witness?

Yes, but it is often viewed as problematic because the arbitral tribunal may question the expert’s objectivity, which can diminish the persuasive force of the evidence. If there are financial constraints and there are no other options, an employee may be the only option.
5. How should parties approach the selection of an arbitrator when expert issues are expected?

Parties should consider appointing an arbitrator with relevant industry or technical experience, while recognizing that the arbitrator cannot substitute personal expertise for evidence.
6. What limits apply to an arbitrator’s use of personal expertise?

An arbitrator may use their background knowledge to understand the issues and question the expert witnesses, but they cannot introduce new technical conclusions or assumptions not presented in evidence. This would open the door to a potential review.
7. When might the arbitral tribunal appoint its own expert?

The arbitral tribunal may appoint its own expert when the parties’ experts appear biased, when their methodologies diverge significantly, or when the tribunal requires neutral assistance. The appointment of an arbitral tribunal expert witness will require protocols in order to ensure procedural fairness.
8. How should parties manage the exchange of expert reports?

The parties and the arbitral tribunal must agree on the number of rounds, the sequence for delivery, and the timing of expert reports, all of which should be set out clearly in the scheduling order. The exchange can be simultaneous or one after the other.
9. What role does methodology play in the persuasiveness of expert evidence?

A transparent, well‑explained methodology enhances credibility. Arbitrators scrutinize assumptions, data sources, and reasoning, and will discount opinions that lack analytical rigor. An internal employee with expertise can often be deployed to ensure that the analytical standards are met.
10. How can in‑house counsel maximize the effectiveness of expert evidence?

In‑house counsel should engage experts early in the dispute, ensure they have full access to the factual record, and work closely with them to present opinions that are clear, objective, and aligned with the overall case theory. In-house counsel should remain actively involved throughout each iteration of the expert report, providing guidance where necessary to maintain coherence, accuracy, and strategic consistency.

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Key considerations