The source of every survey figure in this segment. The Report says its findings are perceptions, not measurements, and that its in-house counsel sample was particularly limited (para 1.4.3). It does not give the number.
03
The client's view
Choosing and paying for experts.
Ben Bury, Director, General Counsel at Gammon Construction Limited, speaks for the client: the party that chooses and pays for the expert. His slides are topics and questions, not conclusions. They ask when a contractor should appoint an expert and who it should appoint; whether the client sees its own lawyers steering the expert; and what value for money looks like. The figures come from the Chartered Institute of Arbitrators' 2026 Report on party-appointed experts. They record what 419 respondents perceive, not what was measured, and the Report says its in-house counsel sample was small.
Choosing the expert, and when
Most of the people CIArb surveyed in 2026 want the expert in early: 71% favour appointment before the arbitration starts, and the Report records Sir Robin Knowles's view that engaging experts only at the hearing stage is inadequate. It still happens late. External counsel blame cost (53%); experts say the main cause is that their role is not understood (42%) (CIArb 2026 para 14.1.2). Two choices follow for a contractor. The first is between a shadow (consulting) expert, whose communications stay privileged, and a testifying expert, whose instructions will be seen. The second is the retainer: what it says about conflicts, and about the expert's firm. In the English courts it is the court, not the parties, that decides whether a conflict matters (Toth v Jarman [112]).
“71% of all respondents favouring appointment during the pre-arbitration stage.”
“engaging expert witnesses only at the evidentiary hearing stage is inadequate.”
“Communications with experts who are not expected to testify (i.e. consulting experts) remain privileged and non-disclosable.”
“it is for the court and not the parties to decide whether a conflict of interest is material or not.”
Who thinks experts are over-instructed?
The 2026 Report asked each group whether experts are over-instructed by counsel, meaning instructions that improperly shape, constrain or direct the expert's opinion (para 5.1.1). Arbitrators (66%), external counsel (60%) and in-house counsel (100%) said often or very often. Experts disagreed: 73% said never or not often (paras 5.1.3 to 5.1.5). Two cautions go with the figures. The Report describes its findings as perceptions, not measured practice, and it says its in-house sample was particularly limited; it does not give the number (para 1.4.3). The question for a client is whether it sees its own lawyers steering its expert, and what it would do about it.
“In-house counsel reported the highest perceived incidence of overinstruction”
“A decisive majority of 73% said that they are "never" or "not often" over-instructed.”
“the findings presented in the Report reflect perceptions, experiences and professional judgments of respondents, rather than independently verified empirical measurements of practice.”
Value for money
Expert evidence is usually a large share of the cost of an international arbitration (CIArb 2026 para 12.1.6), and the ICC Commission reminds arbitrators that experts do not work for free. A client wants evidence that survives cross-examination and cost that stays under control. In the survey, in-house counsel were unanimous against a fact witness doubling as an expert (para 33.1.1), and 83% of them wanted short summaries of reports and expert presentations at the hearing (paras 26.1.1 and 38.1.1). Three questions stay open. Late instruction looks cheaper but, the Report says, compresses the expert's time and raises the overall cost (para 14.1.5). The Hong Kong Construction Court starts from a single joint expert (Redland Precast [15]); arbitration still mostly uses one expert on each side. And an expert appointed by the tribunal does not necessarily cost the parties less (Bell, GAR Guide 2025).
“Retained expert witnesses do not work for free, nor are they inexpensive.”
“the appointment of an expert by the tribunal does not necessarily result in considerably fewer expenses for the parties”
“However, such short term cost savings can prove counterproductive because late instructions compress the time available to produce more robust reports and increase the intensity of the expert witnesses' analysis, ultimately raising overall costs.”
“Single joint expert evidence is preferred and has been used as the starting point for expert directions by the Construction Court.”
Go deeper
Issues for Arbitrators to Consider Regarding Experts: An Updated Report of the ICC Commission on Arbitration and ADR
An arbitrator's view, not survey data.
Katherine Bell, 'Expert evidence in construction disputes: arbitrator perspective', GAR Guide to Construction Arbitration (6th edn)
Toth v Jarman
- [100]-[102] A conflict does not automatically disqualify; the key question is independence; a material or significant conflict will likely lead the court to decline to act on, or admit, the evidence; disclose early.
- [108], [111]-[113] Conflicts not obviously immaterial must be disclosed, at latest with the report (earlier if permission for a named expert is sought); it is for the court, not the parties, to decide materiality; parties cannot agree to keep it from the court.
- [114], [119]-[120] Expert's CV should disclose possible conflicts; recommended declaration of no undisclosed conflict and duty to update.
Judgments of the courts of England and Wales are quoted from Find Case Law under the Open Justice Licence v1.0.
Redland Precast Concrete Products (China) Ltd v AES Steel Mould (Hong Kong) Ltd
CIArb International Arbitration Practice Guideline: Party-appointed and Tribunal-appointed Expert Witnesses
2021 International Arbitration Survey: Adapting arbitration to a changing world
Decide who in the business can call an expert, and when. The survey's answer is early: 71% of respondents favour appointment before the arbitration starts (CIArb 2026 para 2.1.5). The Report calls late instruction a departure from good practice (para 13.1.4).
Keep the shadow expert and the testifying expert distinct in your own mind, even if they come from the same firm. Communications with a consulting expert stay privileged (ICC 2021); a testifying expert's instructions will be described in the report (IBA Rules art 5.2(b)).
Put conflicts in the retainer: the expert's own earlier work on the project, the firm's other instructions, and what happens if a conflict appears later. In the English courts it is the court, not the parties, that decides whether a conflict matters (Toth v Jarman [102], [112]).
Budget for the whole job, not the report. The Report says late instruction compresses the expert's time and raises the overall cost (CIArb 2026 para 14.1.5), and 60% of in-house counsel said an agreement on recovering costs would not fix late instruction (para 15.1.1).
Ask for a short summary with each report and an expert presentation at the hearing. 83% of in-house counsel favoured each (CIArb 2026 paras 26.1.1 and 38.1.1).
Do not let a fact witness double as an expert. In-house counsel were unanimously against it (CIArb 2026 para 33.1.1), and in Hong Kong an expert's connections with a party go to the weight of the evidence (Redland Precast [31]).
The figures are perceptions. The Report says its findings reflect respondents' perceptions and professional judgments rather than independently verified measurements, and that its respondent pool was particularly limited for in-house counsel (para 1.4.3). The 100% figure is a unanimous view within a small group. It is not a measurement of practice.
A single joint expert is the Hong Kong Construction Court's starting point (Redland Precast [15]), but CIArb's 2015 Guideline records why parties resist it: an unfavourable opinion leaves them nothing to challenge. In the 2021 QMUL survey, counsel also warned of a tribunal-appointed expert becoming a de facto fourth arbitrator.
The cost warning cuts both ways. Expert fees increase the cost of an arbitration (ICC 2021), but an expert appointed by the tribunal does not necessarily cost the parties less (Bell, GAR Guide 2025), and under Cap 609 s.54 and HKIAC Rules art 25.4 the parties may still call their own experts to answer the tribunal's expert.