Managing Principal Joshua White and Principal Jessica Resch on Expert Hot Tubbing in International Arbitration

Analysis Group and Latham & Watkins recently hosted an event in London for the Chartered Institute of Arbitrators’ (CIArb) Young Members Group on the use of expert witness conferencing in international arbitration, often referred to as “hot tubbing.”

Analysis Group Managing Principal Joshua White and Principal Jessica Resch acted as opposing experts in a hypothetical damages case study. Latham & Watkins Associate Shreya Ramesh took the role of tribunal chair, guiding the experts through the key issues and testing the areas of agreement and disagreement. The case study showed that conferencing is not just a procedural concept, but an approach that can shape how expert evidence is presented, tested, and understood. The discussion was co-moderated by Analysis Group Manager Arjun Dasgupta and Latham & Watkins Associate Evangeline Tsui.

Hot Tubbing Can Take Several Formats

Expert witness conferencing is not a single fixed procedure. The demonstration compared two different approaches: In one, the tribunal led, putting questions to both experts and inviting them to respond to each other’s views in real time, keeping the discussion tightly focused on the issues the tribunal considered most important. In the other, the experts led with the technical points they considered central and engaged more directly with each other’s analysis. This gave the tribunal a different perspective on where the experts themselves saw the points of disagreement.

In practice, many cases may benefit from a hybrid approach: conferencing with a clear structure and agenda, tribunal control where needed, and room for experts to engage directly as issues emerge.

Where Witness Conferencing Can Work Well

At its best, expert witness conferencing can be a highly effective way to clarify technical evidence. Rather than hearing from experts sequentially, sometimes days or even weeks apart, the tribunal hears them address the same question side by side, making it easier to see where the experts genuinely disagree.

This can be particularly useful in disputes involving quantum or valuation questions, where the tribunal often needs to understand not only each expert’s conclusion, but also the reasoning behind it. A well-run conference can surface important practical questions such as which assumptions are driving the difference, which inputs matter most, and whether the experts are using different methodologies or applying the same one differently.

Conferencing can also help identify which disagreements have the biggest impact on the outcome. That is valuable in complex disputes where expert reports may contain numerous differences, but only a few affect the result.

Points for Counsel to Consider

Despite its advantages, expert conferencing is not a cure-all. Counsel and tribunals should think carefully before adopting it.

A key risk is lack of structure. Without a clear agenda, a free-flowing discussion can become unfocused or dominated by the more outspoken expert, who may not have the strongest analysis and evidence.

Preparation is also critical. Expert conferencing generally works best where the areas of agreement and disagreement have already been narrowed, often through joint expert reports or agreed-upon agendas. An overly broad set of questions makes the discussion inefficient; too rigid an agenda loses the benefit of experts engaging directly as issues become clearer during the discussion.

Counsel should also be alive to witness dynamics; some experts are naturally more comfortable in an interactive format than others. An expert who is measured, cautious, or less forceful should not automatically be seen as less persuasive. It is important to ensure the tribunal hears clear, balanced, and focused answers from both sides – the substance rather than the personalities.

A Tool that Rewards Thoughtful Planning

The practical takeaway for counsel is simple: Propose expert witness conferencing where it will help the tribunal better understand the evidence. Carefully plan the issues to be discussed, the order in which issues will be addressed, who leads the questioning, how experts may respond to one another, and where counsel examination fits into the process.

Designed thoughtfully, expert conferencing can be one of the most useful parts of an arbitration hearing. It can expose weak assumptions, clarify real disagreements, and help tribunals make better-informed decisions.