Related Sector: Expert Witness

Towards the end of 2021, we recounted a Liverpool County Court case where an expert witness was ordered to pay £50,543.85 in costs by way of a non-party costs order. This was due to various issues relating to his conduct and experience. The case was widely reported in the legal press and hailed as a stern warning to expert witnesses about a risk of liability for costs when acting as medico-legal experts.

However, we are pleased to report that the expert in question has successfully appealed this decision and the costs order has now been overturned (see Robinson v Liverpool Hospitals NHS Trust and Mercier [2023] EWHC 21 (KB)).

Our summary below, lists the salient points of this case.

But does it go as far as offering reassurance to experts who may be concerned about the cost implications of Jones v Kaney?


Miss Martine Robinson (the Claimant) brought an action for clinical negligence against an NHS Trust (the Defendant) following dental treatment by a dental surgeon employed by the Defendant. In support of her allegations, she instructed Mr Mercier, a medico-legal expert.

The Claimant later withdrew her claim because under cross examination, Mr Mercier had conceded:

  • 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 sought consent of a patient regarding a GA extraction.

The Defendant applied for a third-party costs order (TPCO) against Mr Mercier. This application was successful at first instance.

Mr Mercier subsequently applied to the High Court to appeal this decision.

Mr Justice Sweeting sitting in the King’s Bench Division of the High Court, carried out a detailed review of the issues of the case, the expert evidence given and his qualifications.

He allowed the appeal, finding that Mr Mercier was qualified to give the evidence, and that any criticisms of the expert did not meet the high threshold in favour of granting the TPCO.

Rational for granting appeal

The Defendant’s application for a TPCO was centred on the contention that as a dentist, rather than a dental surgeon, Mr Mercier lacked relevant expertise to be a medico-legal expert in this case concerning care provided by a dental surgeon. The judge, at first instance, agreed stating that Mr Mercier had stepped outside the boundary of his expertise. He deemed Mr Mercier to be unqualified to give expert opinion about breach of duty and causation in a personal injury case concerning allegations of negligence against an oral and maxillofacial surgeon.

Sweeting J went on to carefully examine ‘’whether the fact that Mr Mercier was not a maxillofacial surgeon disqualified him from giving expert evidence’’ in this case.

In deciding to overturn the TPCO, he identified the following considerations:

  1. Mr Mercier did have the requisite expertise to comment on the relevant issues. The treating dental surgeon was qualified as a dentist. As was the Defendant’s expert. Mr Mercier’s opinion regarding breach of duty concerned an examination that was undertaken by the dental surgeon prior to obtaining the Claimant’s consent for surgery. Therefore, "there could be no sensible suggestion that any different standard applied to the examination of the patient’s teeth and the x-rays to confirm which required extraction as between a surgeon dentist and a general practitioner.’’
  2. The Claimant had an extraction under general anaesthesia because of her fear of dental procedure. If not for her phobia, the treating dental surgeon agreed in evidence, her extraction would have been carried out by a general dental practitioner. The defendant’s expert agreed.
  3. Mr Mercier did not need to be a maxillofacial surgeon to give an opinion on the issues of the case. There was no suggestion that it was not within the competence and scope of a general practitioner dentist to carry out extractions, to take and report on x-rays and to assess the viability of a tooth to determine whether it required extraction. Both he and the defendant’s expert gave their opinions on the point given that it went directly to causation.
  4. There was nothing illogical or partisan about Mr Mercier’s conclusions. In fact, his conclusions had been supported, in part at least, by the defendant’s expert. In addition, the treating surgeon himself acknowledged in evidence an error in failing to identify – prior to taking the Claimant’s consent – that, although two molars were present in the upper left quadrant on the x-ray, only one remained in her mouth.
  5. The experts identified a failure to record a pre-operative examination as falling below the standard to be expected of a reasonable body of “practitioners”. There was no suggestion from the experts that any different standard should be applied to an examination by the dental surgeon as opposed to a general dentist performing an examination prior to an extraction.

The test for ordering a TPCO (as outlined in Phillips v Symes [2004] EWHC 2330) represents a high threshold. It is necessary to establish that the expert acted “in flagrant reckless disregard of his duties to the Court”.

Sweeting J concluded that:

The scope of the suitability of an expert’s expertise is to be judged with reference to the issues at stake and not with reference to the title of or post occupied by the treating clinician.

There may well have been grounds to criticise Mr Mercier’s performance as an expert witness and to attack his conclusions, but this was not an exceptional case and did not involve a flagrant or reckless disregard of an expert’s duty to the court. On the facts of this case, it would not be just to make a costs order against him in any amount.”


This case serves as a useful summary of the principles regarding expert expertise and the threshold that the courts are likely to apply when deciding whether to grant a TPCO against an expert in similar circumstances. It is also illustrative of how important it is for experts to ensure that they have the requisite expertise to provide an opinion on a case. If they have any doubts about their ability to give evidence in a case, experts should reconsider the instruction, speak to their instructing solicitors, and/or seek a second opinion from a colleague or contact.

Whilst the expert in this case was successful in having the TPCO overturned, which does provide some reassurance for experts with regards to any potential liability, there is no guarantee that a court would reach the same decision in another case. In addition, the uncertainty and the costly nature of appeals should, if possible be avoided.

To help expert witnesses carry out their work in compliance with the rules, Bond Solon offers a variety of courses, such as the Civil Law & Procedure course (criminal and family law options available too), Discussions Between ExpertsExcellence in Report Writing. Please visit here to view our full suite of courses.   

Author, Meera Shah

This article was published on 13 February 2023

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