KA-2024-BHM-000008 - [2025] EWHC 2093 (KB)

Appeals on matters expert evidence

The relevant principles are also very helpfully set out in the Wheeldon case, at paragraph 11:

“11 A first instance judge’s assessment of, or evaluations based upon, expert evidence adduced at trial must be approached by an appellate court with similar caution. Whilst it has been said that a reconsideration of an expert’s opinion may be slightly easier than a finding of fact, because the underlying report will be in writing (see Thomson v Christie Manson & Woods Ltd [2005] EWCA Civ 555; [2005] PNLR 38), the same case also provides a salutary warning that, since the evaluation of expert evidence is likely to be bound up with a wider evaluation of matters of fact, an appellate court will still be very slow to intervene. At para 141 of his judgement in Thomson’s case, May LJ said:

“But, even accepting that individual points such as these are amenable to judicial appellate evaluation whatever the expert opinion, no appellate court should cherry pick a few such points so as to disagree with a composite first instance decision which, in the nature of a jig-saw, depended on the interlocking of a very large number of individual pieces, each the subject of oral expert evidence which the appellate court has not heard.”

In the paragraph of the court’s judgment in the Thomson case which is referred to in Wheeldon, May LJ also said the following:

“It is a commonplace that this court will only rarely disturb a judge’s finding of fact reached after hearing oral evidence whose credibility is in issue. It may sometimes be somewhat less difficult to depart from an evaluative judgment of expert evidence, if the evidence is mainly in writing and its evaluation an intellectual process largely unaffected by personal credibility. But that is not this case…..[The judge’s] conclusions are in each instance supported by credible evidence. The existence of other evidence does not render these judgments wrong nor does it persuade me that he should have reached an opposite conclusion. ….Restating evidence and submissions which the judge rejected does not persuade me that the judge was wrong, when the judge’s conclusions were supported, as they were, by the opinions of Christie’s experts.”

Wheeldon, and the authorities referred to therein, make clear that an appellant has a high hurdle if he or she wishes to persuade an appellate judge that the trial judge was not entitled to come to the conclusion that he or she came to on matters of fact and expert evidence, including evaluations and conclusions based on that evidence.