In the first half of 2026, two significant pieces of guidance were issued for expert witnesses involved in international arbitration.
Firstly, in January 2026, the Singapore Society of Construction Law published the Protocol on the use of experts’ joint statements in arbitration, with the primary aim of creating a flexible, uniform framework for best practices in international and domestic arbitrations.
In July 2026, the Chartered Institute of Arbitrators (CIArb) published the Report on Party-Appointed Expert Witnesses in International Arbitration: Effectiveness and Best Practice. The report recognises the critical role expert witnesses play in arbitration and seeks to ensure that expert evidence is prepared, presented and tested in a way that supports the efficient, fair and informed resolution of disputes.
In this article, we’ll explore both these pieces of guidance in more depth and summarise the key principles for expert witnesses.
The protocol
What are joint statements?
Joint expert statements are prepared jointly by the parties' experts following a meeting between them. They set out all the issues that have been agreed, the issues still disagreed on and the reasons for these differences.
Why was the protocol created?
According to the report, 74% of arbitrators, 74% of external counsel and 60% of in-house counsel support establishing joint expert witness reports or statements as a “norm in every arbitration with a view of achieving effectiveness”.
Despite this support, the use of joint statements in international arbitration has historically lacked a clear procedural framework. The protocol's authors recognise that early and constructive engagement between experts can save time and costs while improving the quality of expert evidence in Singapore-seated arbitrations and beyond.
The seven core principles
The protocol provides seven core principles designed to reinforce expert independence, encourage constructive expert engagement and ensure transparency throughout the arbitral process.
Parties and tribunals are free to adopt (in whole or in part) and adapt the protocol according to the needs of the case.
The principles are drawn on those already found in English Court Civil Procedure Rules (CPR) Part 35 (and Practice Direction), the English Technology and Construction Court (TCC) Guide, the Academy of Experts’ Guidance on Joint Statements and the CIArb International Arbitration Practice Guideline on Party-Appointed and Tribunal-Appointed Experts.
The protocol's seven core principles can be summarised as follows:
- Core Principle 1: Each expert giving evidence in the joint statement must provide a declaration of competence and independence in the agreed form. The tribunal may disregard in whole or in part - or adjust the weight to be placed on - any expert opinion or testimony that fails to comply with its terms.
- Core Principle 2: Expert discussions and associated working materials, including drafts and communications, are to be conducted on a without prejudice basis and may not be used in the proceedings without the parties’ agreement. Unless ordered by the tribunal or agreed by all parties, counsel should not attend expert meetings. If they do attend, their role should be limited strictly to answering questions posed by the experts and advising on matters of law.
- Core Principle 3:Counsel may assist experts in identifying the issues to be addressed in the joint statement and in providing instructions and all relevant and material documents but must not seek to influence the content of the joint statement or participate in its drafting.
- Core Principle 4: Unilateral communications between an expert and the tribunal are prohibited. This is to preserve transparency and due process.
- Core Principle 5: The timing of expert meetings is flexible and should reflect the nature of the case and the kind of expert evidence required. Early meetings before exchange of individual reports are generally considered sensible in complex matters.
- Core Principle 6: Each expert should provide full reasons for disagreeing with the other on any particular issue and, where possible, indicate the quantitative effect of that disagreement on the outcome of the case.
- Core Principle 7: The tribunal has discretion to direct experts to confer after the hearing and produce supplementary statements - jointly or separately - to address issues arising from the tribunal’s determinations during or following the hearing.
The report
The report serves as an advisory resource drawing together data, practitioner perspectives and emerging best practices.
The data is organised around four key themes:
1) Communication between expert witnesses, the tribunal and counsel.
2) Timetables and timing of involvement of expert witnesses.
3) Ensuring the tribunal understands expert evidence.
4) The hearing and post-hearing.
Experts may adopt whichever recommendations apply to their practice or the particular case they are instructed on.
How can expert witnesses benefit from the report?
According to the report expert witnesses can benefit from:
- Insight into how tribunals and parties may perceive the effectiveness and challenges of expert witness evidence.
- Guidance on areas where greater transparency, structure or early engagement may enhance the usefulness of expert witness opinion.
- Context for differing practices encountered across seats, institutions and procedural traditions.
What are the key findings of the report?
Across all four themes, one clear message emerged: expert evidence is considered more effective when tribunals take an active and engaged role in managing it.
In particular, the tribunal should maintain focus on the issues in dispute and engage directly with the methodologies adopted by expert witnesses in their work, rather than treating expert witness evidence as a matter to be left entirely to party presentation.
For example, there is near universal support among expert witnesses (95%) for the proposition that tribunals should put questions to them following submission of first expert witness reports.
The report also makes several references to an expert witness's overriding duty to the tribunal. Although this approach is not universal across all jurisdictions, the report treats it as the prevailing standard in international arbitration.
Conclusion
The protocol and the report reflect a growing emphasis on improving the quality, efficiency and effectiveness of expert evidence in international arbitration. While neither document imposes mandatory requirements across all arbitrations, both provide valuable guidance on how experts, counsel and tribunals can work together to ensure that expert evidence assists, rather than complicates, the resolution of disputes.
A common theme running through both publications is the importance of early engagement, transparency, independence and active tribunal involvement. The protocol offers a practical framework for the preparation of joint statements, while the report provides useful insight into the practices and procedures that stakeholders believe contribute most effectively to the arbitral process.
For expert witnesses, these publications serve as important reference points and signal the continued evolution of expectations surrounding expert evidence in international arbitration.
How can we help
Expert witnesses who embrace these evolving best practices and continue to provide independent, objective and well-reasoned opinions will be best placed to assist tribunals in reaching fair, efficient and informed decisions.
Bond Solon provides training covering all the core skills and knowledge expert witnesses require to fulfil their role compliantly and effectively. We also offer university certified training programmes that are widely regarded as the industry gold standard by instructing parties.