Related Sector: Expert Witness

On 1st October, an expert witness was ordered by the court to pay costs of £50,543.85.

Where did the expert go wrong?

The costs order was made in the case of Robinson v Liverpool University Hospital NHS Foundation Trust v Dr Mercier 2021.

The claimant had alleged that a maxillofacial surgeon had negligently failed to remove one of her teeth, following a referral by her dentist.

Dr Mercier, a general dental practitioner (“GDP”), was instructed by the claimant and produced a report and gave evidence in support of the claim. At the end of his evidence, however, the claimant withdrew her claim because Dr Mercier had had to concede under cross examination:

  • That he had never trained or practised as a maxillofacial surgeon
  • That the defendant’s expert witness, a consultant maxillofacial surgeon, was better placed to comment on the standards to be met in practice
  • That he had had no experience in general anaesthetic (“GA”) extraction in over 20 years
  • That he did not work in a hospital setting
  • That he had never consented a patient regarding a GA extraction

In short, it was clear that he lacked the relevant expertise.

Nevertheless, he sought to give an opinion that the surgeon was negligent, displaying what the judge, Ms Recorder Hudson, described as “a gross lack of understanding of the seriousness of his role” as an expert witness.

Although advancing the view that the surgeon was negligent, he accepted that the surgeon’s referral of the claimant back to her GDP was a proper course of action – thereby accepting that the Bolam test was not made out and there was no causal link to any damage. The judge described his evidence as “simply absurd” and held that he fundamentally did not understand the correct legal test and how it should be applied.

Dr Mercier acted with a “flagrant and reckless disregard of his duty to the court” and his evidence was “grossly unhelpful and wholly unreliable”.

The judge was clear that he should never have prepared a report on subject matter in which he had no expertise. She ordered him to pay the defendant’s costs because the claim would never have been brought but for his report – the claim had had no chance of success.


During the costs order hearing, there was some argument that the defendant should have informed the claimant that their expert was not properly qualified; the judge was having none of it. It is the expert witness’ duty to identify to those instructing them and to the court the limits of their expertise and at all times to stay strictly within those limits. The expert witness’ duty to the court is not delegable.

This case highlights the dangers of working as an expert witness without being fully trained and prepared. Any expert witness must make a thorough study of their duty to the court so that they can be confident that they are working within their obligations; they cannot rely on their instructing party, or on anyone else in the case, to warn them.

A regular and attentive engagement with the relevant procedural rules is absolutely fundamental.

Bond Solon has produced a web-based learning package, “Introduction to the Civil Procedure Rules”, which takes the expert through their duty to the court and its application at every stage of the court process. It is an essential reminder for the experienced expert witness as well as introduction for those who are new to this work.

Better to be trained than face an order to pay £50,000!

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