Robinson v Liverpool University Hospital NHS Foundation Trust v Mercier revisited

Thea Wilson looks at the next development in this case in which the Defendant had sought a third-party costs order against an expert witness, because, after this expert’s oral evidence at trial, the Claimant had withdrawn her claim.

Followers of 12 King’s Bench Walk’s Clinical Negligence blog may recall my article on tips for dealing with expert evidence in light of the case of Robinson v Liverpool University Hospital NHS Foundation Trust v Mercier, published at the beginning of 2022.

The Facts

For those not familiar with the case, the facts, briefly, were that the claimant, Miss Robinson, sued the NHS Trust for clinical negligence after they failed to extract a tooth in the course of dental surgery. The medico-legal expert upon whom Miss Robinson relied was Mr Mercier, a dentist. In his report on breach and causation, he made a number of criticisms of the oral & maxillofacial surgeon who performed the claimant’s dental surgery and stated that they had breached their duty of care and fallen below the standard of a reasonably competent dentist/maxillofacial surgeon. The matter came to trial in December 2020. Following Mr Mercier’s oral evidence at trial but before the defendant’s expert had given evidence, Counsel for the claimant withdrew the claim. The Recorder was not told why the case was withdrawn and did not give a judgment on the merits. The defendant NHS Trust, Respondent in the appeal, sought a Third Party Costs Order against Mr Mercier.

At first instance, Recorder Hudson took the view that Mr Mercier had failed to properly consider whether he was an appropriate expert to comment on the actions of an oral and maxillofacial surgeon; that Mr Mercier had acted as an advocate for the claimant rather than as an impartial expert; that there were major gaps in his report (including whether he had seen some fundamental radiography); and that he had either misunderstood, or failed to properly address, the relevant legal test for breach of duty. He held that an expert witness was not immune from the sanction of compensating those who had suffered by evidence given recklessly in flagrant disregard of his duties to the court and that it should have been obvious to Mr Mercier at the outset, and at various stages throughout the proceedings, that he was not the appropriate expert. Mr Mercier was found to have not made any efforts to assist the court, but instead to have wilfully stuck to his case theory irrespective of the questions asked or the evidence given. His evidence was held to be grossly unhelpful and wholly unreliable, showing a flagrant reckless disregard for the duties of an expert to the court.

Having found a case in negligence established, the Recorder Hudson considered whether there was a causal link between Mr Mercier’s actions and the defendant’s wasted costs. He held that, despite Mr Mercier’s attempt to lay the blame on the claimant’s legal representatives for concocting a case out of his report, but for the initial report the claim would not have been brought and the NHS Trust would not have been put to considerable expense defending it. A Third Party Costs Order was therefore made against Mr Mercier.

On Appeal

Mr Mercier appealed, and the case was heard by Sweeting J who gave judgment in January 2023 (Case reference: [2023] EWHC 21 (KB)).

Sweeting J cited with approval Phillips v Symes [2004] EWHC 2330 and Peter Smith J’s statement that an expert who, by evidence given in flagrant reckless disregard of his duties to the Court, causes significant expense to be incurred should face a costs order. But emphasised that the evidence must be reckless and in flagrant disregard for the experts’ duties. It is an order to be exercised only exceptionally.

In Mr Mercier’s case, the basis of the Respondent’s application for costs was that Mr Mercier was the wrong expert and should have appreciated that at the outset or during the course of litigation. The other criticisms made were illustrative of this central assertion.

Sweeting J considered that the extraction complained of was something carried out by dental practitioners, not just maxillofacial surgeons and that Mr Mercier did not need to be a maxillofacial surgeon to express an opinion on it. The experts had agreed that there were breaches in the pre-operative examination and that breach had been identified in Mr Mercier’s first report, even though the trial judge took the view that it had not been pleaded.

Sweeting J held that the judge was wrong to conclude that Mr Mercier had stepped outside the boundary of his expertise in giving his opinion about breach of duty and causation in relation to the examination carried out prior to the attempt to extract the tooth. Whilst there may well have been grounds to criticise Mr Mercier’s performance as an expert witness and to attack his conclusions, this was not an exceptional case and it did not involve a flagrant or reckless disregard of an expert’s duty to the court. It was not just to make a costs order against him in any amount.


Although the appeal judgment in Robinson v Mercier will be some comfort to medicolegal experts and bad news for defendants, the central messages from the case regarding expert evidence remain the same. To claimant lawyers, the implications of this judgment are minimal; whatever happened to their expert, as a result of the errors made along the way the Claimant pursued to trial a case that she was forced to withdraw following her expert’s oral evidence. The Claimant received no compensation in the case despite the treating surgeon having accepted that mistakes had been made (although neither the Recorder at first instance nor Sweeting J commented on the merits of the underlying claim, so it is uncertain how strong it would have proven or whether causation flowed from those breaches); the Claimant’s lawyers lost out on a significant share of costs. For this reason, as a claimant practitioner, it will remain vital to choose the right expert in the right discipline, review the report for compliance with care, and test the expert, in conference if possible. A further clear takeaway from Sweeting J’s judgment is the importance to those drafting pleadings of clearly understanding the expert’s position on breach and in ensuring that it is fully and accurately pleaded.

For defendant practitioners considering making applications for Third Party Costs Orders against claimant experts, it is clear that whilst it still remains possible to obtain these orders the bar is very high and it is only the exceptional case with extreme wrongdoing by experts in which a court will entertain such an application.

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