Recent cases have highlighted ways in which experts have been discredited in court. They range from fundamental misunderstandings of expert obligations to relying on the wrong standard of proof or changing position under cross-examination. The experts all left themselves exposed to criticism from judges.
Limitations of data
In Mew v General Dental Council [2026] EWHC 1116 the expert avoided setting out the limitations of the data in his report, believing it would be sufficient for him to explain it when being questioned in court. This, in the judge’s words, “belied a fundamental misunderstanding of the obligations upon a CPR compliant expert”.
In his judgment, Charles Bagot KC highlighted the duty set out in CPR Part 35 for expert witnesses to include a statement of truth in their reports, as part of which any limitations to the evidence should be laid out.
CPD35.3.2(8) expressly states: “If the expert is not able to give an opinion without qualification, state the qualification”.
In not doing so, the expert demonstrated a lack of familiarity with these rules and lost the confidence of the judge.
Judge calls out medical expert
Then in clinical negligence case, Alexander v HCA International Ltd & Anor [2026] EWHC 1284, the judge was compelled to comment on an expert’s intractability on a key issue and their failure to properly consider the balance of probabilities.
The expert for the claimant urged the court to consider evidence on the use of a drug called Diclofenac, which in his opinion the claimant should have received, while the defendant’s experts relied on broader medical evidence. One of the defendant’s experts went as far as to rule out discussion of the use of Diclofenac at all.
“I find that this position is untenable”
On assessment of the evidence concerning Diclofenac the judge concluded its use reduced risk beyond the 50% required to satisfy the civil standard of proof, leading him specifically to question the defendant expert’s stance that it should not form part of the court’s discussion.
Sitting as Deputy High Court Judge, HHJ Richard Roberts, said: “I find that this position is untenable and would constitute substandard and negligent practice”.
He said the expert’s evidence on Diclofenac “diminishes his credibility as an independent expert and results in my being able to place less weight on his evidence”. Moreover, the judge noted that having taken this position in his report, the defendant expert had changed his opinion in the joint statement.
The judge also found that the defendant’s experts had relied on the wrong standard of proof in their opinion in the case. Instead of working on the balance of probabilities, which is the required standard in civil clinical negligence, the experts were working to a higher scientific standard.
HHJ Roberts said: “The standard of proof in a civil clinical negligence case is the balance of probabilities, namely more than 50%. The standard is not the scientific standard of a confidence interval of 95%. [The expert] is applying the standard required to submit a paper to a medical journal. In so doing, he fails to address the question to be answered by the Court of whether the Claimant would have avoided pancreatitis on the balance of probabilities.”
A change of position? Don’t wait until court
Finally, in Greening-Steer v Ainge [2026] EWHC 1239, Mr Justice Ritchie criticised an expert who waited until cross-examination in court to re-assess his opinion considering new evidence.
The case concerned a personal injury claim in which the claimant’s expert initially accepted the claimant’s account of his injuries and advised that he would need various interventions, including domestic carers, adjusted accommodation and mobility aids, and was unable to work.
In February 2026, the expert gained access to videos which he accepted showed better than “anticipated” mobility, stability and gait. The expert altered his opinion slightly, advising that the claimant may be capable of some, but not full-time, work. He maintained most of his prior opinion, suggesting that the condition could worsen with age or in the cold.
Under cross-examination, the expert’s opinion changed substantially. He conceded that the only explanation for the difference between the claimant’s condition in his original assessment and the videos was that the claimant had consciously exaggerated his symptoms.
He then adjusted his assessment of the claimants needs, withdrawing the suggestion that he would need any domestic help until old age or that he was incapable of full-time work, except that he should not climb ladders. He also admitted that he had not been shown the claimant’s schedule of loss.
Ritchie said: “I consider that he should have set out his true opinions on malingering in his last report, rather than waiting until cross-examination to reveal them to the Court.”
Much as in the first case, this expert has failed to meet his obligation to the court by leaving it until cross-examination to fully assess all the evidence and form his opinion. Where new or contradictory evidence was presented to him, he should have re-assessed his opinion and flagged where he thought any evidence might be missing or incomplete.
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