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Expert Evidence – Avoiding fatal failure

On 29th November 2023 the Supreme Court released its decision in the eagerly awaited case of TUI UK Ltd (Respondent) v Griffiths (Appellant) [2023] UKSC 48.

TUI tells a catastrophic tale in failing to challenge expert evidence adequately at the appropriate time and the latent risk of relying on ‘trial by ambush’ tactics. It provides useful guidance on the correct procedural approach to follow where expert evidence is likely to be disputed.


While on an all-inclusive package holiday, Mr Griffiths suffered a serious gastric illness which caused him long-term problems. As a result, Mr Griffiths sued TUI for breach of contract. He relied on expert evidence from a microbiologist as to the cause of his sickness to prove his claim. The expert concluded that the illness was, on the balance of probabilities, caused by contaminated food and / or drink.

TUI did not require the expert to attend cross-examination and it did not submit any evidence of its own. The evidence was therefore uncontroverted. Remarkably, TUI waited until the eleventh hour to criticise the expert report and only did so as part of its closing submissions. Nevertheless, TUI successfully convinced the judge that deficiencies in Mr Griffiths’ expert’s report meant that Mr Griffiths had failed to prove his case.

On appeal, the High Court overturned the trial judge’s decision, concluding that it could only reject an uncontroverted expert report if it was a bare ipse dixit, i.e. just a one-sentence report stating the expert’s conclusion (which, in Mr Griffiths’ case, it was not). However, the Court of Appeal subsequently upheld an appeal by TUI, concluding that there were no authorities to support the bright line rule adopted by the High Court.

The Supreme Court’s decision

When the case reached the Supreme Court, the Court stressed the critical importance of the quality of the expert’s reasoning. However, in conducting a trial in an adversarial system, the judge must ensure that the trial is fair. In this regard, Lord Hodge (giving the unanimous decision) endorsed the long-established rule set out in Phipson on Evidence (itself deriving from the rule in Browne v Dunn (1893) 6 R. 67), (the Phipson Rule).

The Phipson Rule states that a party must challenge in cross-examination the evidence of any witness if it wishes to submit to the court that the evidence should not be accepted on that point, and that if a party decides not to cross-examine on a particular point, it will be difficult for it to submit that the evidence should be rejected.

The Supreme Court also clarified that the Phipson Rule applies to both witnesses of fact and expert witnesses and regardless of whether the challenge is made on the basis of dishonesty, accuracy or other inadequacy. Its application is universal.

However, the Court did explain that the rule is flexible and will depend on the circumstances of the case. The court identified 7 potential exceptions to its application. Notably, these included where the expert has already been given sufficient opportunity to address criticism or clarify his or her report (such as by way of focused CPR 35.6 questions) but has failed to respond satisfactorily; potentially where there has been a serious failure to comply with the requirements of CPD PD 35; or where the report is based on an incorrect/incomplete history or ill-founded assumptions.

Key take aways going forward 

Expert evidence is often critical to the determination of complex, high value claims.  Getting it wrong can be fatal. The key points arising from TUI are as follows:

  • Oppose the other side’s evidence at the earliest opportunity, whether that is achieved by obtaining your own expert evidence, cross examination, written questions via Part 35.6, or relying on one of the exceptions listed by Lord Hodge.
  • If using Part 35.6 questions, ensure they are specifically focused on and give adequate notice of the challenges you wish to make. Note that TUI had raised CPR 35.6 questions, but these did not adequately alert the other side to the challenges it ultimately made in closing submissions. Be clear at the outset.
  • Cross examination need not be long, it just needs to be focused on the challenges to the evidence.
  • Parties must ensure that the expert’s report complies with the relevant rules (and note that the Guidance for the Instruction of Experts in Civil Claims 2014 goes further than CPR 35 by stating that “generally the summary [of conclusions] should be at the end of the report after the reasoning.”).

TUI followed several other cases in 2023 where the Court specifically criticised deficiencies in relation to expert evidence.  Examples included:

  • failure by an expert to remain impartial and address all the evidence fairly, and advancing explanations for the first time during cross-examination [1] 
  • expert evidence that was unsatisfactory and ill thought through, and where the Claimant’s experts had intended to give oral evidence without fully addressing key changes in evidence since their reports had been compiled [2]
  • failure by the parties to agree a joint expert, where the Claimant had failed to engage properly with the appointment of an expert and only did so at a late stage [3]


The above examples underline the importance of following best practice whenever expert evidence is required, whether you are obtaining or challenging such evidence. Whilst they certainly aren’t rocket science, the key considerations set out above should be at the forefront to ensure there is no risk of them inadvertently being overlooked by the urgency of a matter or the unusual nature of the expert evidence required. We are yet to see decisions following TUI, but it certainly presents a credible risk of uncontested (or inadequately contested) evidence being accepted at face value.

Ultimate care must therefore be taken, not only to ensure the quality, compliance and robustness of your expert’s own report, but also that you shout loud and clear at the outset, and indeed consistently thereafter, with any challenges to the other side’s report.  

[1] Rowbottom v Howard (Deceased) [2023] EWHC 931 (KB)
[2] Scarcliffe v Brampton Valley Group Ltd [2023] EWHC 1565 (KB)
[3] Gheewalla v Rasul [2023] EWHC 2074 (Ch)

This article was originally published in thoughtleaders4.

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