Originating in the Australian Competition Tribunal in the 1970s and refined extensively by the Australian Federal Court, "hot-tubbing" — the practice of taking evidence from opposing experts concurrently, in a panel format, rather than sequentially — has become an established feature of complex construction, infrastructure and energy arbitration in the UAE. For parties and counsel unfamiliar with the technique, understanding how and when it is deployed in DIAC and DIFC-seated proceedings can materially affect hearing strategy.
What Hot-Tubbing Involves:
Rather than each party's expert giving evidence in isolation — examined, cross-examined and re-examined in a purely linear sequence — hot-tubbing brings experts of the same discipline together after all factual evidence has been heard. Each expert typically summarises their position, the tribunal poses questions directly, and the experts respond to and question one another, with counsel's role in shaping the discussion often reduced compared with traditional cross-examination.
Why UAE Tribunals Are Increasingly Using It:
DIAC and DIFC-seated tribunals handling technically complex construction, energy and infrastructure disputes have found concurrent evidence particularly valuable because it:
• Reduces the risk that experts default to entrenched, partisan positions, since views must be justified in real time to professional peers as well as the tribunal • Allows the tribunal to test competing methodologies directly against one another on the same question, rather than reconciling two separate, sequentially delivered reports • Shortens hearing time by removing duplicated background explanation that would otherwise be repeated by each expert in turn • Better reflects the flexible, less adversarial procedural culture that arbitration — as distinct from court litigation — is designed to offer
Where Hot-Tubbing Adds Most Value in UAE Disputes:
Concurrent evidence tends to be most effective in disputes involving:
• Delay and disruption analysis, where competing programme methodologies can be tested question-by-question against the same factual record • Quantum valuation disputes, particularly where the underlying disagreement is more about assumptions than raw calculation • Structural and technical causation disputes, where multiple experts (structural, geotechnical, MEP) may need to engage with overlapping questions of contributing cause
Preparing Experts for Concurrent Evidence:
Experts instructed in DIAC or DIFC-seated arbitrations where hot-tubbing is contemplated should prepare differently from a traditional cross-examination-only hearing:
• Be ready to engage directly and professionally with the opposing expert's reasoning, not just restate a prior written position • Understand and be able to articulate precisely where disagreement stems from differing factual assumptions versus differing professional judgment • Approach the process as a genuine, collegial exchange of professional opinion — tribunals are notably unimpressed by experts who treat the hot tub as an extension of adversarial advocacy • Be prepared for the tribunal, rather than counsel, to lead much of the questioning, requiring experts to respond directly and concisely to technical points
A Note of Caution:
While concurrent evidence has clear advantages for expert testimony, tribunals and commentators have cautioned against extending the same technique to factual witnesses, where the risk of one witness's account subtly influencing another's recollection is a genuine concern. In UAE practice, hot-tubbing is therefore reserved almost exclusively for expert evidence, and its use should be directed only by an experienced tribunal alert to these distinctions.
Getting the Most from Concurrent Evidence:
For parties in DIAC or DIFC-seated construction, infrastructure and energy disputes, the value of hot-tubbing depends heavily on the groundwork laid earlier in the proceedings — joint conferral, agreed factual records, and clearly identified areas of disagreement. Experts who have already engaged constructively with their counterpart through the procedural stages of the case tend to perform far better in a concurrent evidence session than those encountering the opposing expert's reasoning for the first time at the hearing itself.