Related Sector: Expert Witness, Witness Familiarisation

The uncontroverted expert witness – a landmark case

 On Wednesday 29th November 2023, the Supreme Court handed down a judgment on TUI UK Ltd (Respondent) v Griffiths (Appellant) [2023] UKSC 48. This is a fascinating case that has moved through the civil courts system on various appeals, since the initial County Court action in 2017.

The primary point of appeal to the Supreme Court concerned the following question: in what circumstances can a trial judge decide that a claimant has not proved their case, where the evidence of a claimant’s expert witness on the central issue in the case has not been challenged by a defendant on cross-examination?

The case at first instance

Mr and Mrs Griffiths and their youngest son went on an all-inclusive package holiday to a hotel resort in Turkey. While staying at the hotel, Mr Griffiths suffered a serious stomach upset, which left him with long term problems.

Mr Griffiths sued the travel company, TUI UK Ltd. At trial, he presented evidence from an expert witness, Professor Pennington, who concluded that, on the balance of probabilities, the likely cause of Mr Griffiths’ stomach upset was the food and drink served at the hotel.

TUI did not cross-examine Professor Pennington. In addition, it did not present any expert witness evidence of its own on the central question of causation. In his closing submissions, however, TUI’s counsel argued that the deficiencies in Pennington’s report, such as incomplete explanations and a failure expressly to discount other possible causes, meant that Mr Griffiths had failed to prove his case.

The trial judge criticised Pennington’s report on the basis that it did not show that it was more likely than not that the food and drink at the hotel had caused Mr Griffiths’ stomach upset.

She concluded that Mr Griffiths had not proved his case and dismissed his claim.

The case on first appeal

Mr Griffiths appealed to the High Court.

The judge, Martin Spencer J stated that the appeal raised a fundamental question concerning the proper approach of the court towards uncontroverted expert evidence.

He began by stating that the following two questions had to be answered:

  1. Whether a court is obliged to accept an expert’s uncontroverted opinion, even if that opinion could properly be characterised as an ipse dixit (that is, opinion made by an individual based solely on their own authority, without any supporting evidence or proof).
  2. If not, what were the circumstances in which the court would be justified in rejecting such evidence?

Spencer J concluded that a court could only reject an uncontroverted expert report if it were, literally, a bare ipse dixit - such as a one-sentence report stating the expert’s conclusion. This would not be the case with regards to an expert report that is compliant with the rules under CPR PD 35.

Reviewing CPR PD 35, he reminded the court that it does not expressly require the expert to set out his reasoning for his conclusion. A failure to set out such reasoning might diminish the weight to be attached to the report but the weight to be attached to the report “is not a consideration: that only arises once the report is controverted.” He then went on to say that if there had been controverting expert evidence, Pennington would have expanded upon his reasoning, for example in a meeting of experts and a joint statement. But there was none. In addition, his opinion was not challenged by cross-examination.

The second question was whether Pennington’s report was a bare ipse dixit or otherwise so deficient as to have entitled the court to reject it. Despite the “serious deficiencies” identified by the trial judge, the report substantially complied with the CPR PD 35 and therefore was not a bare ipse dixit.

Spencer J allowed Mr Griffiths’ appeal.

The case on second appeal

TUI then appealed to the Court of Appeal.

In a judgment dated 7 October 2021 ([2021] EWCA Civ 1442; [2022] 1 WLR 973) the majority of the Court of Appeal (Asplin LJ and Nugee LJ) allowed the appeal on the following grounds:

  1. There is no strict rule that prevents a court from considering the content of an expert’s report that complies with CPR PD 35, where it has not been challenged by contradictory evidence. In addition, there is nothing inherently unfair in challenging expert evidence in closing submissions.
  2. Pennington’s report did not comply with CPR PD 35 because it did not provide the range of opinion required by TUI’s lawyers following their questions under CPR Part 35.6.
  3. Pennington did not provide some reasoning in support of his conclusion (Kennedy v Cordia and para 62 of the Civil Justice Council’s “Guidance for the Instruction of Experts in Civil Claims” (2014))

The case on final appeal

The Supreme Court unanimously allowed Mr Griffith’s appeal.

It held that the trial judge was wrong to allow TUI to make the detailed criticisms of Professor Pennington’s report and to accept those submissions. In doing so, she denied Mr Griffiths a fair trial.

The Court also held, looking at the evidence that Mr Griffiths presented at trial, including Pennington’s evidence, that he had showed that it was more likely than not that the food and drink at the hotel had caused his stomach upset.

What can we learn from this final appeal?

The Supreme Court confirmed the general rule in civil cases - that a party must challenge by cross examination (and not in closing submissions) the evidence of any witness of the opposing party on a material point, which he or she claims should not be accepted by the trial judge. As the justice system is adversarial, this requirement gives the witness an opportunity to explain or clarify his or her evidence or defend his or her professional reputation if challenged and allows the trial judge to make a proper assessment of all the evidence in the case.

The Court did, however, explain that this requirement is a not rigid one, and gave seven examples of when it might be relaxed:

  1. When the matter to which a challenge is directed is collateral or insignificant such that fairness to the witness does not require there to be an opportunity to answer or explain.
  2. When evidence is manifestly unbelievable and an opportunity to explain on cross-examination would make no difference.
  3. When an expert report makes an assertion with no reasoning in support.
  4. When there is an obvious mistake on the face of an expert report
  5. When a party’s fact evidence may be contrary to the factual basis on which the expert witness made their report.
  6. When an expert witness has been given a sufficient opportunity to respond to criticism of, or otherwise clarify, their report other than on cross-examination.
  7. When an expert witness’ report does not comply with the requirements of CPR PD 35.

In applying the above principles, the Court held that in the interests of justice, Pennington should have been given the opportunity to respond to TUI’s criticisms in their counsel’s closing submissions. TUI chose not to challenge Pennington’s report on cross examination or lodge its own expert report. In addition, the questions TUI asked under CPR PD 35 did not focus on the matters, which it later criticised.

While Pennington’s report lacked detail and could have included more reasoning, it was not a bare assertion. The Court was also satisfied that he provided further explanation of his reasoning in response to TUI’s CPR PD 35 questions.


This Supreme Court case provides expert witnesses and instructing solicitors with a detailed and unquestionable insight into how a court is likely to treat the evidence of an uncontroverted expert.

It is reassuring that in reaching their decision, the Supreme Court judges placed much emphasis on justice and the right of a witness (factual or expert) to respond to all challenges of their evidence.

Meera Shah

This article was first published on 7 December 2023


Please leave a comment

  • Dr Deneys Schreiner CEng - Technical Director

    08 Dec 2023 12:29

    This is a very informative summary. It has clarified for me the position regarding the need for challenges to an EW report to be made in the right way, ie by another expert or i cross examination. The right to explain or clarify an opinion under cross examination or by responding to another expert's report must be upheld. As I understand the summary, content that is not so challenged with the opportunity to explain or clarify must be taken by the court to be accepted unless any of the exceptions provided can be demonstrated.

  • Dr Adam Abdelnoor - Expert Witness (Psychology)

    08 Dec 2023 12:29

    This had to be the outcome of the Supreme Court appeal. Otherwise, it would open the door in almost any case for legal teams to delay challenging expert evidence until final submissions, and avoid the risk that the expert can successfully rebut their challenges. My only other observation is that Professor Pennington laid himself open to criticism when he failed to ensure his report comprehensively met all the PD35 rules.

  • Anonymous

    08 Dec 2023 12:50

    as interesting as ever

  • Andrzej(Andrew) Wojcik - Consultant Orthopaedic / Spinal Surgeon

    08 Dec 2023 15:34

    Very clear and informative explanation

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