Do experts have a duty to disclose previous criticisms of their evidence?
In this article, Trinity's Patience Abladey explores the recent High Court commercial litigation decision in JSC Commercial Bank Privatbank v Kolomoisky & Ors [2025] EWHC 1987 (Ch) which has potential ramifications for a wide range of civil practitioners. The case is about a Claimant bank’s allegation of misappropriation of funds.
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. Indeed, there is no obligation in CPR Part 35 or in the Practice direction to make such a disclosure. The Civil Justice Council Guidance for the instruction of experts in civil claims is also silent on this.
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 wide-ranging duty of candour to experts giving evidence in civil proceedings. 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 an 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 Peregrine Aviation, Mr S was cross-examined on the fact that he had been criticised in the 2010 and 2012 decisions. 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. In fact, his evidence appeared to be 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 v Kolomoisky) that led Mr Justice Trower to conclude that Mr S ought to have disclosed that earlier criticism when giving evidence before him. The failure to do so was, Mr Justice Trower concluded, ‘a breach of his own personal duty to the Court’.
The judicial comments noted above can be said to be strictly obiter, however, it is suggested that it would be prudent of civil practitioners to explore these matters with experts upon whom they seek to rely on and make disclosures where appropriate. For expert witnesses, another passage in JSC (para 1230) makes it clear that past judicial criticism does not necessarily mean that an expert cannot, in subsequent proceedings, find favour with the Court, as Mr Justice Trower accepted.