Hong Kong Courts Reject Allegations Of Arbitrator Bias And Lack Of Independence And Impartiality

The Hong Kong courts recently rejected allegations of arbitrator bias and a lack of independence and impartiality in three separate decisions delivered over a five-week period (O v. S [2026] HKCFI 4910, COB v. FCB [2026] HKCFI 4162 and MB v. HB [2026] HKCFI 4437).

Although the decisions concerned challenges to arbitral awards rather than the arbitrators themselves, the same well-established legal test for apparent bias is relevant in both contexts, namely: whether an objective fair-minded and informed observer, having considered the relevant facts, would conclude that there was a real possibility that the tribunal was biased.

The decisions illustrate the approach of the Hong Kong courts to apparent bias and the closely related concept of independence and impartiality, as well as the high bar that applicants will face to establish apparent bias or a lack of independence and impartiality and successfully rely on them to challenge arbitral awards.

They also contain valuable judicial discussion of arbitrator disclosure obligations, the application of the International Bar Association Guidelines on Conflicts of Interest in International Arbitration (IBA Guidelines), the treatment of witnesses, and the implications of a witness giving evidence before the same arbitrator in different arbitrations.

The most recent decision features a detailed discussion of the legal framework in relation to apparent bias and a definitive finding rejecting allegations of bias for the purpose of challenging an HKIAC award (O v. S [2026] HKCFI 4910). The two earlier decisions feature technically preliminary findings on bias and independence and impartiality made for the purposes of deciding whether to grant security for HKIAC and ICC awards pending challenges by the award debtors, albeit in both cases the court made clear that it did not consider the complaints against the arbitrators would ultimately succeed (COB v. FCB [2026] HKCFI 4162 and MB v. HB [2026] HKCFI 4437, previously reported here in relation to the security issue).

Key points on bias

• Actual or apparent bias are not themselves specified grounds to challenge an arbitrator or an award rendered by them under the Hong Kong Arbitration Ordinance (Cap. 609) (Arbitration Ordinance). If established, however, actual or apparent bias may give rise to: (i) "justifiable doubts concerning the arbitrator's impartiality or independence", such as to justify a challenge to the arbitrator pursuant to section 25 of the Arbitration Ordinance / Article 12 of the UNCITRAL Model Law; (ii) a ground for setting aside the award pursuant to section 81 of the Arbitration Ordinance / Article 34 of the UNCITRAL Model Law; and/or (iii) a ground for resisting enforcement of the award pursuant to Part 10 of the Arbitration Ordinance.
• The Hong Kong courts will be slow to make findings of actual or apparent bias. Actual bias has an especially high threshold (requiring that "the decision maker was influenced by either partiality or prejudice, and it has been demonstrated that he was actually prejudiced"), and has been described as "largely redundant" given the ground of apparent bias (COB v. FCB [2026] HKCFI 4162, discussed below, citing the English case of Locabail (UK) Ltd v. Bayfield Properties Ltd [2000] QB 451).
• In determining whether there is apparent bias pursuant to the "objective fair-minded and informed observer" test, the court is likely to carefully consider and accord significant weight to the content of the award itself (where available), although all other relevant circumstances will also be considered (O v. S [2026] HKCFI 4910). 

Key points on disclosure and witnesses

• The IBA Guidelines and relevant literature may provide a "starting point" for analysis, but whether an arbitrator should make a disclosure will depend upon the circumstances (O v. S [2026] HKCFI 4910).
• A failure to discharge a duty of disclosure will not automatically lead to a conclusion that there is a real possibility of bias (O v. S [2026] HKCFI 4910).
• Disclosure will not necessarily be required simply because an arbitrator has previously considered evidence from a witness in an earlier unrelated arbitration, but probably will be required where (for example) extreme or adverse comments were made on the integrity of the witness in the earlier case (O v. S [2026] HKCFI 4910).
• Where an arbitrator is prevented by confidentiality from making a disclosure, for example about a witness in a previous case, they may have to consider not accepting the appointment (O v. S [2026] HKCFI 4910).
• Witnesses giving evidence in arbitrations should expect to be subjected to robust cross-examination, including questions from the tribunal in appropriate circumstances, and this in itself is unlikely to justify allegations of actual or apparent bias (COB v. FCB [2026] HKCFI 4162).

1. No apparent bias where presiding arbitrator had ruled against witness in previous case

In O v. S [2026] HKCFI 4910, the award debtor applied to set aside an HKIAC partial award which it alleged was tainted by apparent bias because the presiding arbitrator had in an earlier (apparently unconnected) arbitration ruled against a witness who gave evidence for the award debtor in the later arbitration.

Background 

The dispute arose under an investment management agreement pursuant to which US$117 million was invested by the award debtor as investment manager into a bond issued by a third-party company. The award creditor claimed in the arbitration that (amongst other things) the agreement had been terminated or automatically expired, the managed assets should be returned to it, the investment in the bond represented a dissipation of its funds at a time when there was already a dispute between the parties, and it was entitled to damages for the award debtor's failure to return the managed assets.

On the agreement of the parties, the proceedings were bifurcated into phase 1 addressing liability and already quantified damages, and phase 2 for damages yet to be quantified.

At the phase 1 oral hearing, the founder and chairman of the bond issuer's parent group gave evidence as a witness for the award debtor. In the partial award, the tribunal observed that it was "puzzling" that the witness was apparently familiar with the bond but was unable to provide details about it. It expressed sympathy with the award creditor's dissipation argument, but considered it unnecessary to make a finding because it had already ruled in favour of the award creditor on termination and the return of the managed assets. The tribunal also deferred until phase 2 the determination of questions not just of quantum but also of liability in relation to certain damages claims on which it did not consider that it had been sufficiently briefed in phase 1. 

Approximately two weeks after the partial award was issued, the witness attended a business meeting with the managing director of the award debtor, at which he disclosed that he had previously testified as a witness in a separate arbitration with the same presiding arbitrator, in which the tribunal had made findings adverse to the parties for whom he had given evidence. The witness indicated that he had not recognised the presiding arbitrator at the later hearing for a variety of reasons, including the gap of nearly one year between the hearings and the fact that he had testified in the later arbitration remotely from a laptop.

There was no dispute that the presiding arbitrator had not disclosed anything about the prior arbitration.

Challenges to presiding arbitrator and award

The award debtor filed a challenge to the presiding arbitrator under the HKIAC Rules which was rejected by the HKIAC. 

In parallel, the award debtor applied to set aside the partial award on the basis of (i) apparent bias on the part of the presiding arbitrator and (ii) the tribunal's alleged failure to comply with the bifurcation which had been agreed by the parties and ordered by the tribunal. The application was heard by Deputy High Court Judge Gary CC Lam.

In support of the allegation of apparent bias, the award debtor argued that: the evidence of the witness was squarely in issue; the tribunal had implicitly made findings on the reliability and credibility of that evidence; the presiding arbitrator should have disclosed his involvement in the earlier arbitration given its temporal proximity to the later arbitration; the presiding arbitrator must have received confidential information in the prior arbitration about the witness, the group that issued the bond and the nature and probity of their business, but was bound by confidentiality not to disclose that information, which placed the award debtor in the predicament of being unable to investigate the matter; the presiding arbitrator was "argumentative" and "defensive" in his written response to the challenge filed with the HKIAC, suggesting that he had "something to hide"; and the tribunal's failure to observe the bifurcation agreement added to the real possibility of bias.

Legal principles 

In addition to the basic legal test for apparent bias (discussed above), the court noted that:

• It was neither reviewing nor bound by the HKIAC's decision, and the issues before it had to be determined de novo.
• There is a "premium on frank disclosure" by arbitrators because of the private nature and limited public oversight of arbitral proceedings, as pointed out in comments by Lord Hodge DPSC in the leading English case of Halliburton Co v. Chubb Bermuda Insurance Ltd [2021] AC 1083 (which the judge agreed with "as matter of common sense").
• The arbitrator's duty of disclosure, and whether and how it has been discharged, is among the relevant circumstances to be considered by the fair-minded and informed observer, but a failure to disclose does not automatically lead to a conclusion that there is a real possibility of bias.
• There is no "absolute rule" on whether an arbitrator should disclose the fact that they had previously considered evidence from a fact or expert witness in an earlier, unrelated arbitration. Commentary in a leading treatise on international arbitration suggesting that disclosure was not required, and the absence of a requirement for disclosure of such circumstances in the IBA Guidelines, could be taken as a "starting point", but the position would depend on the circumstances.
• Disclosure probably would be required, for example, if the arbitrator had made "extreme, adverse comment on the witness’s integrity" in the earlier case. If the arbitrator was prevented by confidentiality from disclosing that fact in the later arbitration, they might have to consider declining the appointment.
• For the purpose of setting aside an award, proof of apparent bias is in itself insufficient, and the complainant has the burden of showing that, but for the apparent bias, the outcome would have been different (in other words, that the complainant has been prejudiced) (applying Grand Pacific Holdings Ltd v. Pacific China Holdings Ltd (No 1) [2012] 4 HKLRD 1).

Decision 

The court undertook a detailed review of the partial award and quoted extensively from it in the decision. The partial award had itself considered the relevance of the bond, the evidence of the witness and related documentary material. On a fair reading of the partial award, the evidence of the witness was only one of several factors taken into account by the tribunal. The tribunal’s description of aspects of his evidence as "puzzling" was a fair comment which any reasonable tribunal would make. A reasonable and fair-minded observer would not perceive the partial award to make any unfavourable finding or finding of dishonesty against the witness.

The court accepted that: (i) the award debtor's strongest point was its inability to know what had occurred in the confidential prior arbitration; (ii) given the temporal proximity of the proceedings, it must have "rung the bell" to the presiding arbitrator that the witness had appeared in the earlier arbitration; (iii) the presiding arbitrator's answer to the challenge filed with the HKIAC "appeared argumentative" (although there might have been a range of reasons for this); and (iv) a fair-minded and informed observer might consider that the presiding arbitrator did make some adverse comments on the witness in the earlier arbitration, but did not make the disclosure because of his financial interesting in accepting the appointment in the later arbitration (although this would remain only a "doubt"). However, none of those points in themselves necessarily gave rise to a conclusion of apparent bias.

Considering all the relevant circumstances including the partial award, the court considered that (i) the fair minded and independent observer would conclude that there was no real possibility of bias, and (ii) the outcome of the partial award would have been the same in any event, such that the partial award should not be set aside even if there had been apparent bias. The court also rejected the bifurcation ground, finding that there had been no breach of the bifurcation order.

2. No bias where quantum expert subjected to robust cross-examination

In COB v. FCB [2026] HKCFI 4162, the award debtor (the main contractor for a Hong Kong construction project) resisted the enforcement of an HKIAC award on due process and public policy grounds, alleging actual and apparent bias arising from the sole arbitrator’s treatment of its quantum expert.

The complaint included allegations that the arbitrator had "launched a scathing and unwarranted attack" on the expert's report on the first day of the hearing, developed a "grudge and/or bias" against the expert arising from the cross-examination conducted on behalf of the award creditor, conducted his own research on the cost of a waste disposal machine and taken the expert by surprise with questions about it, and subjected the expert to "grossly unfair and unequal treatment".

Mimmie Chan J rejected those allegations on a preliminary basis, emphasising that parties, lawyers and experts must be accustomed to the adversarial nature of arbitration and litigation, including vigorous cross-examination and robust questioning of witnesses. Experienced arbitrators were accustomed to such cross-examination and would not easily be led to form biases or grudges as a result of it. The arbitrator had been entitled to test the expert evidence, and the questioning was reasonable and not oppressive or unfair. There was therefore no factual basis for actual bias or for a fair-minded and informed observer to conclude that there was a real possibility of bias.

Although this assessment was technically made on a preliminary basis, the judge noted that all the evidence in the challenge to enforcement of the award had been filed, the application was clearly without merit, and the award was "manifestly valid". This suggests that the decision effectively represents the settled and final view of the court on the bias allegations. 

3. Personal friendship and professional relationship between arbitrators held not to impair independence or impartiality

In MB v. HB [2026] HKCFI 4437, the Mainland PRC award debtor sought to adjourn the enforcement of a US$70 million ICC award pending the determination of a set-aside application at the courts of the seat in Paris, relying in part on alleged undisclosed links between the presiding arbitrator and the arbitrator nominated by the award creditor.

The relevant circumstances included the fact that the two arbitrators had sat together in four previous arbitrations, their prior membership of the same chambers (which had ceased before the arbitration), the fact they had authored a book together, and their personal friendship.

On a preliminary review, Mimmie Chan J held that the evidence said to establish a duty of disclosure or impugn the independence and impartiality of the arbitrators was "tenuous to say the least". The prior arbitrations in which the two arbitrators had sat together had all closed before the arbitration began, they had ceased to be members of the same chambers approximately 5 years before the arbitration began, the fact they had authored books together had been disclosed, and their personal friendship and professional relationship could not be evidence of such closeness which would influence their decision-making process. 

The judge considered that (i) the alleged links between the arbitrators did not fall within the "Orange List" under the IBA Guidelines, (ii) no duty of disclosure arose in relation to them, and (iii) an objective and fair-minded observer would not conclude that there was any real possibility that the arbitrators lacked independence or impartiality. Again, although these findings were strictly preliminary, they clearly represented the considered view of the court. 

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