Testing of Evidence does not Spell Bias: A Look at Hong Kong Court of First Instance's Decision in COB v FCD [2026] HKCFI 4162
When does robust questioning of an expert by an arbitral tribunal cross the line into bias?
The Hong Kong Court of First Instance recently considered, amongst others, this issue in COB v FCD [2026] HKCFI 4162 (“COB”), where a party alleged that the arbitrator had developed a ““grudge” and/or bias” against its quantum expert and had effectively made up his mind to reject the expert’s evidence (COB at [17]).
The Court rejected those allegations (COB at [36]).
The decision is a useful reminder that rigorous scrutiny of expert evidence does not, without more, amount to bias: testing an expert’s methodology, assumptions and evidential foundation is part of the tribunal’s adjudicative function (COB at [28] – [29]).
Background
The underlying dispute arose from a Hong Kong construction project in which the plaintiff was the main contractor and the defendant was the developer.
Following an HKIAC arbitration, the arbitrator issued a final award requiring the defendant, amongst other things, to pay the plaintiff the outstanding payment certified under the construction contract (COB at [1]).
The defendant subsequently sought to set aside the enforcement order on grounds of lack of due process, serious irregularity, breach of natural justice and that enforcing the award would be contrary to public policy (COB at [3]).
A central complaint concerned the treatment of the defendant’s quantum expert, H. The defendant alleged that criticism of H’s evidence caused the arbitrator to develop a “grudge and/or bias” against him and that the arbitrator had prejudged the issues (COB at [5(3)], [17]).
The decision
The Court reiterated that actual bias, which is a high threshold, requires proof that the decision-maker was influenced by partiality or prejudice. The Court cited the English decision in Locabail (UK) Ltd v Bayfield Properties Ltd [2000] QB 451 at 471 in this regard (COB at [18]).
For apparent bias, the test is whether a fair-minded and informed observer, having considered the relevant circumstances, would conclude that there was a real possibility that the tribunal was biased. In this regard, the Court cited its earlier decision in Jung Science Information Technology Co Ltd v ZTE Corporation [2008] 4 HKLRD 776 (COB at [19]).
The Court observed that arbitration is adversarial. Parties and their legal representatives may vigorously challenge witnesses and experts in pursuit of their case, and experienced arbitrators are accustomed to such exchanges. Arbitrators are “… accustomed to such cross-examination and would not be easily led to form bias, or “grudges” as suggested in this case, to the extent that his/her judgment would be clouded by such bias or prejudice, to reach a conclusion without any factual basis or evidential foundation”. (COB at [27]).
More fundamentally, an arbitrator has a duty to evaluate competing expert evidence and decide whether an expert’s conclusions are sound and reliable, which necessarily involves putting questions to experts and testing their cases (COB at [28]).
Thus, where the tribunal has concerns about an expert’s evidence, it “was fair” that such concerns should be raised with the expert, “… instead of keeping these questions unanswered and dismissing them in his final decision”. (COB at [29]).
Thus, while the defendant relied on the arbitrator repeatedly asking H whether his figures were estimates and why he had not sought invoices or actual payment records supporting the claimed expenses as evidencing a grudge and/or bias (COB at [26]), the Court regarded those questions as directed at understanding the basis of H’s assessment and valuation and considered them reasonable, stating that the Court did not view the questions as “oppressive, or harsh, or scathing, or unfair”(COB at [30] – [31]).
Indeed, while the arbitrator did his own research to find the costs of a waste disposal machine and pose questions to H (COB at [5(5)]), the Court did not find that the research and the arbitrator’s questions were “unreasonable and warranted”, especially as the Court found that H was given the opportunity to answer and the parties’ counsel had the opportunity to address the arbitrator as well (COB at [30])
The Court also rejected any suggestion of unequal treatment. The arbitrator had similarly questioned the plaintiff’s expert on her valuation methodology, the relevance of actual costs and payment records and whether quotations amounted to evidence of actual payment (COB at [32]).
The defendant further complained that H should have been permitted to produce another expert report after it became apparent that he had misunderstood an earlier direction (COB at [26]). The Court rejected that argument, finding that the tribunal is the master of the proceedings and is best placed to decide whether further rounds of expert evidence should be permitted (COB at [34]).
Importantly, the Court stated that “[t]here must be an end to the filing of evidence in any case”, and it was within the arbitrator’s case management powers to refuse to give H a further opportunity to put in another report, which would then have had to be considered by the counterparty and the opposing expert (COB at [34]).
Key takeaway
The Court found no factual basis for concluding that the arbitrator was actually prejudiced against H or the defendant, nor any circumstances from which a fair-minded and informed observer could conclude that there was a real possibility of bias (COB at [36]).
Thus, while rigorous questioning by a tribunal may not always occur, when it does occur, this conduct, in and of itself, would not necessarily amount to biasness. As the Court observed, in arbitration proceedings, it would be reasonable to expect a tribunal to put questions to an expert to test their case.
Of course, this is not to say that rigorous questioning by a tribunal may not, in certain circumstances, cross the line such that the tribunal may be regarded as having impermissibly descended into the fray, and thus leading to a breach of the rules of natural justice that may justify a setting aside of the arbitral award.
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