The framework

The Ordinance gives the tribunal its toolkit

The Arbitration Ordinance (Cap 609) gives the UNCITRAL Model Law the force of law in Hong Kong, with changes. Two of the changes matter for experts. Hong Kong replaced the Model Law's duty to give each party a full opportunity to present its case with a duty to give a reasonable opportunity (s.46(3)(b)). And the tribunal must use procedures that suit the case and avoid unnecessary delay or expense (s.46(3)(c)). Together they give a tribunal room to limit expert evidence: one expert a discipline, page limits, or no late reports.

The tribunal is not bound by the rules of evidence. It may receive any evidence it considers relevant and gives it the weight it thinks right (s.47(3)). So in a Hong Kong arbitration an argument about a weak or conflicted expert is usually about weight, not admissibility.

Two further powers complete the toolkit. Any expert report the tribunal may rely on must be sent to the parties (s.52, which adopts Model Law art 24(3)). Unless the parties agree otherwise, the tribunal may also decide how far to take the initiative itself in finding the facts and the law (s.56(7)). It may order samples, observations and tests on property in issue (s.56(1)(d)(ii)). The duty of fairness in s.46 still applies: the parties must be able to deal with whatever the tribunal does.

The Ordinance was last amended in 2022. These provisions have not changed since 2011. The Department of Justice ran a consultation on amending the Ordinance from 28 September to 27 October 2026, with a Bill targeted for early 2027. None of its 25 issues touches the provisions on procedure and evidence.

“to act fairly and impartially as between the parties, giving them a reasonable opportunity to present their cases and to deal with the cases of their opponents”

“When conducting arbitral proceedings, an arbitral tribunal is not bound by the rules of evidence and may receive any evidence that it considers relevant to the arbitral proceedings, but it must give the weight that it considers appropriate to the evidence adduced in the arbitral proceedings.”

“an arbitral tribunal may, when conducting arbitral proceedings, decide whether and to what extent it should itself take the initiative in ascertaining the facts and the law relevant to those arbitral proceedings.”

The rules you choose: HKIAC, IBA, CIArb

The HKIAC Administered Arbitration Rules 2024 have no article on party-appointed experts. The tribunal's general powers over evidence in art 22 do the work. Each party proves the facts it relies on (22.1). The tribunal decides admissibility, relevance, materiality and weight (22.2). It decides how a witness or expert is examined (22.5), and it may send an expert out of the hearing room (22.7). Tribunal-appointed experts are in art 25. The tribunal sets the expert's terms of reference after consulting the parties. The parties see the report and may comment on it. Either side may still call its own experts at the hearing. And art 11 applies by analogy, so a tribunal expert is held to the arbitrators' standard of impartiality and independence, and can be challenged.

The IBA Rules on the Taking of Evidence in International Arbitration (2020) say more about party experts. The report must describe the expert's instructions, state his independence from the parties, their lawyers and the tribunal, and describe the methods, evidence and information used (art 5.2). The tribunal may order the experts to meet and to record what they agree, what they do not, and why (art 5.4). At the hearing the tribunal has complete control (art 8.3) and may have witnesses questioned together, which the Rules call witness conferencing (art 8.4(f); in the 2010 Rules this was art 8.3(f)).

The CIArb Protocol for the Use of Party-Appointed Expert Witnesses (2007) differs from the IBA Rules in one main respect. The experts meet before they write their reports, to list the issues and the tests they will run (art 6). The expert's opinion must be impartial and objective (art 4.1, in the text CIArb publishes today). No revised Protocol has been issued, though CIArb's July 2026 Report on party-appointed experts signals one. The same Report found the Protocol little used.

Neither the IBA Rules nor the Protocol applies unless the parties or the tribunal adopt them. In P1 v D, an HKIAC tribunal's first procedural order said it would be guided by the IBA Rules, which applied as guidelines and were not binding [3.37]. That is one example. We found no published source on how often HKIAC tribunals adopt any of these instruments.

“The arbitral tribunal may determine the manner in which a witness or expert is examined.”

“in such a manner that witnesses be questioned at the same time and in confrontation with each other (witness conferencing)”

“After consulting with the parties, the arbitral tribunal shall establish terms of reference for the expert, and shall communicate a copy of the expert's terms of reference to the parties and HKIAC.”

“4.1 An expert's opinion shall be impartial and objective.”

“the IBA Rules only applied as guidelines and were not binding or mandatory”

Borrowing from the Hong Kong courts

The Rules of the High Court (Cap 4A) set out a Code of Conduct for expert witnesses in Appendix D. The Code applies by its terms to experts instructed for proceedings in the court (O.38 r.35(2)). It does not bind an expert in an arbitration unless the parties or the tribunal adopt it. Nothing stops a tribunal adopting it, and it is a natural default in Hong Kong because every expert who now gives evidence in the High Court must sign its declaration. We found no published source on how often tribunals do so. The Code's most useful rule for a construction case is paragraph 13. At the experts' meeting the expert exercises his own professional judgment. He must not act on any instruction or request to withhold or avoid agreement.

Practice Direction 6.1 governs the Construction and Arbitration List. Paragraph 15 sets a standard sequence for expert evidence. The court identifies the subjects and the number of experts and frames specific questions for each subject (15(2) to (4)). The experts exchange provisional reports without prejudice (15(5)). They meet, again without prejudice, to agree a common opinion on the questions (15(6)). They sign a joint report of what is agreed and what is not (15(7)). Final reports then deal only with the remaining questions and say why the other expert's views are wrong (15(8)). The sequence is a court direction, not an arbitration rule, but a tribunal can adopt it in a procedural order. It differs from the usual arbitral order of full reports, reply reports and then a joint statement.

In the Construction List a single joint expert is the court's starting point (Redland Precast [15]). Arbitration still runs mostly on party-appointed experts.

“the experts in each subject are to meet on a without prejudice basis to agree a common opinion on the questions within their subject.”

“A reference to an expert witness in this Part or Appendix D is a reference to an expert who has been instructed to give or prepare evidence for the purpose of proceedings in the Court.”

“An expert witness shall exercise his independent, professional judgment in relation to such a conference and joint report, and shall not act on any instruction or request to withhold or avoid agreement.”

“why any opposing expert's views on each such question are wrong.”

“Single joint expert evidence is preferred and has been used as the starting point for expert directions by the Construction Court.”

What the Hong Kong courts have said

Four decisions of the Hong Kong courts set the limits.

Paklito Investment Ltd v Klockner East Asia Ltd (1993). A CIETAC tribunal appointed its own experts. Their report went beyond the case put, and the losing party had no chance to comment on it or to call evidence in reply. Kaplan J refused to enforce the award, because the party had been unable to present its case. The decision was under the old Ordinance (Cap 341), and the only text available is a copy on the judge's own website, so it is cited here and not quoted.

Hebei Import & Export Corp v Polytek Engineering Co Ltd (1999). The Court of Final Appeal enforced a CIETAC award although the tribunal's experts had inspected equipment, with the chief arbitrator present, without notice to one party. That party had received the experts' report and had every chance to comment on it and to challenge it [13], [102]. The lack of notice gave some cause for complaint [24], but a party that wants to rely on an irregularity must say so promptly. It cannot carry on with the arbitration and keep the point up its sleeve for use after the award [75]. V v M (2026) applies the same rule to a party that complained, after the award, that the tribunal had not appointed its own expert: it should have asked for one [60].

Pacific China Holdings Ltd v Grand Pacific Holdings Ltd (2012). An ICC tribunal struck out new authorities that one party's foreign-law expert had put into the joint expert report, and refused leave to rely on them. The Court of Appeal held that this was a case management decision within the tribunal's discretion [68]. Only an error serious enough to undermine due process justifies setting aside, and a party that has had a reasonable opportunity to present its case will rarely show that [105]. The Court of Final Appeal's Appeal Committee refused leave to appeal and endorsed that approach ([2013] HKCFA 13 [5]).

CS v HKR (2024). The parties to a reclamation sub-contract chose an experienced quantity surveyor as arbitrator. He used his own expertise to prefer one quantum expert's valuation on some points and the other's on others. Mimmie Chan J refused leave to appeal. An arbitrator may accept one expert's valuation over another's, and may take parts of each, and that is a question of fact, not law [34]. The Court of Appeal dismissed an appeal on other questions and affirmed her order in July 2026 ([2026] HKCA 1142). The practical lesson is to raise the arbitrator's own expertise at the first procedural meeting. HKIAC's checklist for that meeting asks the question (item 17).

“A party who has had a reasonable opportunity to present its case would rarely be able to establish that he has been denied due process.”

“an arbitrator is entitled to accept the valuation of one expert over another's, and doing so is neither "plainly wrong" nor "open to serious doubt".”

“The respondent was given a copy of the experts' report and an opportunity to deal with it.”

“a party to an arbitration who wishes to rely on a non-compliance with the rules governing an arbitration shall do so promptly and shall not proceed with the arbitration as if there had been no non-compliance, keeping the point up his sleeve for later use after an award is made”

“This naturally extends to where the arbitrator decides to accept one part of an expert's valuation, and another part of another expert's valuation, on the basis of the arbitrator's own expertise.”

“it was open to M to apply for such appointment if it considered that it was necessary to do so, instead of waiting for the Tribunal to order the appointment on its own accord.”