Lessons Learned in International Arbitration: What Not To Do With Expert Evidence, Quantum and Procedure

Further Insights from Beale & Co’s International Arbitration Practice

In a companion article, we examined the mistakes that parties most commonly make when preparing and presenting their cases in international construction arbitration, from failing to establish a coherent project narrative to fielding the wrong witnesses. This second article turns to three further areas where avoidable errors routinely prove costly: expert evidence, quantum and procedural strategy.

These issues arise with striking regularity across the international arbitrations in which Beale & Co is instructed. In each case, the lesson is the same: the error is not in the underlying position, but in how it is advanced. The following observations are drawn from our practice and are intended as a practical guide to what not to do.

Instructing Partisan Experts

Expert evidence plays a central role in construction arbitration, particularly in relation to delay and quantum. However, one of the most damaging mistakes a party can make is to instruct experts who function as advocates rather than as independent advisers to the tribunal. Tribunals in this field are experienced and well equipped to distinguish between genuine expert assistance and partisan opinion dressed up as analysis.

This is especially apparent in concurrent evidence sessions, where experts are examined side by side. Weak methodologies, unjustified assumptions and overly partisan positions are exposed rapidly in this setting, often with devastating consequences for the instructing party’s credibility.

For claimants, overreliance on supportive but methodologically weak expert opinion can undermine the credibility of the entire case. For respondents, the corresponding error is to deploy aggressive but poorly reasoned critiques that fail to engage substantively with the opposing analysis. This is an approach that tribunals find equally unpersuasive.

The lesson: do not treat expert evidence as an extension of advocacy. Expert evidence is most effective when it is transparent, methodologically sound and genuinely independent. Tribunals are far more persuaded by balanced and reasoned analysis than by conclusions that appear to have been driven by the interests of the instructing party.

Treating Quantum as an Afterthought

Quantum is too often treated as a secondary issue; a purely accounting exercise to be addressed once liability has been established. This is a serious mistake. In practice, quantum is subject to the same rigorous scrutiny as liability, and a failure to give it proper attention from the outset can be fatal to an otherwise well-founded claim.

One of the most common weaknesses we encounter is the use of global or high-level quantum claims that are not clearly linked to specific project events. Assertions of productivity loss or aggregated cost claims, advanced without clear evidentiary support or causal connection, are unlikely to withstand challenge and will frequently be rejected in their entirety.

For claimants, the burden is to demonstrate not only that loss has been incurred, but that it flows directly and demonstrably from the events relied upon. For respondents, the focus must be on testing those causal links with precision and identifying the gaps in the supporting evidence that undermine the claim.

The lesson: do not defer quantum to the end of the process or present it as a global figure untethered from the facts. Successful quantum claims are those that tie costs directly to identifiable project events and are supported by contemporaneous records, not retrospective reconstruction.

Neglecting Procedure as a Strategic Tool

Procedural decisions in construction arbitration are frequently treated as administrative formalities. This is a significant missed opportunity. Decisions regarding bifurcation, the sequencing of issues, the scope and format of expert evidence, and the structure of the procedural timetable can each have a material impact on the trajectory and outcome of the case.

By way of example, bifurcation of liability and quantum may permit early resolution of threshold issues and create meaningful opportunities for settlement. Conversely, compressed timetables or poorly structured hearings can severely limit the effectiveness of technical evidence and curtail a party’s ability to present its case fully.

Both claimants and respondents have a role in shaping procedure, and strategic choices at this stage can materially influence how the tribunal engages with the issues and how effectively each party’s case is communicated.

The lesson: do not treat procedural decisions as mere housekeeping. Every procedural choice should be approached strategically and aligned with the overall case theory. Parties that engage actively and thoughtfully with procedure gain a significant tactical advantage.

Key takeaways

The mistakes examined in this article share a common characteristic: they are avoidable. In Beale & Co’s experience, international construction arbitrations are rarely lost because the underlying case lacks merit. They are lost because of failures in execution: in how expert evidence is deployed, how quantum is presented, and how procedural opportunities are used or squandered. Parties that approach these aspects of their case with the same rigour and strategic discipline as they apply to liability will be materially better placed to achieve a favourable outcome.

If you have any questions regarding the information discussed in this article, please contact the authors.