A recent High Court decision in commercial litigation has generated significant interest in the expert witness community. It also has potential ramifications for civil litigators.
The issue concerns the duty of expert witnesses to disclose to the court and opponents previous judicial criticism. To date, many commentators might have considered that expert witnesses in civil proceedings would owe no such duty, even if it might be regarded as tactically unwise to remain silent. There is no obligation to make such a disclosure set out in CPR Part 35 or in the Practice Direction. The Civil Justice Council Guidance for the instruction of experts in civil claims is also silent on this.
Despite this, the leading practitioner’s text, Expert Evidence: Law and Practice by Hodgkinson and James, suggests that such a duty does arise. This is viewed in the context of the application in the Criminal Procedure Rules, 19.3(3)(c), which places a duty upon a party seeking to introduce expert evidence to serve with the report ‘notice of anything of which the party serving it is aware which might reasonably be thought capable of undermining the reliability of the expert’s opinion, or detracting from the credibility or impartiality of the expert’. The same duty is extended to the expert by virtue of rule 19.2(d)(ii), so long as they are aware of it.
In R v Henderson [2010] EWCA Crim 1269, the Court of Appeal ruled that while the Criminal Procedure Rules, as they then were, contained no obligation on defence experts to reveal adverse judicial criticism from past cases, a failure to do so would be contrary to the overriding objective. It was also likely to cast suspicion upon the cogency of the opinion and to damage the case of the party calling the evidence. This is now reflected in the Criminal Practice Direction 7.1.4(c), which makes disclosure of adverse judicial comment mandatory. However, in trials based upon conflicting expert evidence, to reach a verdict, juries need assistance to understand how to distinguish between a reliable expert and an unreliable one. These prescriptive rules are designed to help them achieve that. As such, there exists a body of rules and associated case law that place criminal litigators (and the reporting experts) under a duty of candour when it comes to the historical litigation standing of expert witnesses.
In JSC Commercial Bank Privatbank v Kolomoisky and others [2025] EWHC 1987 (Ch), however, Mr Justice Trower appeared to extend this broad duty of candour to experts giving evidence in civil proceedings. This was a large commercial dispute between a Ukrainian bank and two of its founding shareholders, plus six companies allegedly owned or controlled by them. The bank alleged that the defendants had unlawfully extracted $1.9bn before nationalisation. Experts were called to value various assets. Mr S gave evidence for Mr Kolomoisky regarding the valuation of aircraft. Although Mr Justice Trower said his opinions were offered honestly without straying into advocacy, his credibility was nevertheless undermined by his failure to disclose criticism of his evidence made in three previous decisions: Pindell Ltd v Airasia Berhad [2010] EWHC 2516 (Comm); ACG Acquisition XX LLC v Olympic Airlines [2012] EWHC 1070 (Comm); and Peregrine Aviation v Laudamotion [2023] EWHC 48 (Comm).
In ACG Acquisition XX LLC, the criticism was that Mr S had given evidence on issues that covered similar points in Pindell. Despite this, he had failed to give proper disclosure in the subsequent proceedings. To fail to disclose the material, unhelpful to those instructing him in ACG Acquisition XX LLC, of which he was aware due to his participation as an expert in Pindell, plainly breached the prohibition not to omit to consider material facts which detracted from his opinion (PD35 2.3).
In Peregrine Aviation, Mr S was cross-examined on the fact that he had been criticised in the 2010 and 2012 decisions. As to this, Mr Justice Henshaw agreed that the previous adverse judicial comment should have been disclosed with his report. There was no suggestion, however, that the issues covered in the earlier proceedings were similar to those in Peregrine. The basis of requiring disclosure was not set out in the judgment, which contained no other significant criticism of Mr S. Indeed, in many respects, his evidence was preferred by the court.
It was Mr Justice Henshaw’s acceptance that such a disclosure ought to have been given in Peregrine (in a decision handed down three days before he was cross-examined in JSC Commercial Bank Privatbank v Kolomoisky) that led Mr Justice Trower to the conclusion that Mr S ought to have disclosed that criticism when giving evidence before him. The failure to disclose that was, Mr Justice Trower concluded, ‘a breach of his own personal duty to the court’.
Unlike in criminal proceedings, however, there is no specific duty to disclose adverse judicial comment contained in the CPR. Furthermore, there was no suggestion that Mr S had, either in Peregrine Aviation or in JSC Commercial Bank Privatbank, omitted to disclose a material fact which might detract from his opinion (as was the case in ACG).
The effect of Mr Justice Trower’s decision, therefore, is to equate the obligation to disclose previous adverse judicial comment, even if it is not material to the issues before the court, with that which is expressly codified in criminal proceedings. This is a significant extension.
Ours is an adversarial system. It might be argued that before commanding a party to voluntarily make damaging concessions about unrelated matters of credibility, a clear justification must exist. It does in the criminal jurisdiction, but can the same be said in civil? While the comments in question are strictly obiter, it is suggested that civil litigators would be wise to explore these matters with experts upon whom they rely and make disclosures where appropriate. For expert witnesses, another passage in JSC (para 1230) makes it clear that past judicial criticism does not mean that an expert cannot, in subsequent proceedings, find favour with the court, as Mr Justice Trower accepted.
Richard Edwards, Richard Edwards & Co
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