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| 13 minutes read

TUI and the 7 exceptions: “uncontroverted” expert reports and the requirements of a fair trial

On 29 November 2023, the Supreme Court handed down judgment in the case of Tui v Griffiths [2023] UKSC 48, overturning the majority decision of the Court of Appeal. 

The appeal considered the issue of when a trial judge could decide that a claimant had not proved their case in circumstances where the evidence of a claimant’s expert witness on the central issue in the case – which was not illogical, incoherent or inconsistent, based on any misunderstanding of the facts, or based on unrealistic assumptions –  had not been challenged by a defendant through cross-examination of that witness. 


The case concerned an all-inclusive package holiday at a hotel resort in Turkey, which Mr and Mrs Griffiths had been on with their youngest son. Over the course of that holiday, Mr Griffiths suffered a serious stomach upset and was diagnosed with acute gastroenteritis, leaving him with long term gastrointestinal problems, which were likely to be permanent. 

Mr Griffiths sued TUI Ltd, the travel company from whom he had purchased the holiday. At trial, Mr and Mrs Griffiths gave uncontested evidence as to factual matters. Mr Griffiths also presented evidence from Professor Pennington, an expert microbiologist, who concluded that the likely cause of Mr Griffiths’ stomach upset was the food and drink served at the hotel. 

The report of Professor Pennington was admitted into evidence at trial. The defendant had put Part 35 questions to Professor Pennington, but did not call any evidence or their own, nor did they ask that Professor Pennington attend trial to be cross-examined. Professor Pennington’s uncontroverted expert report was the only expert evidence on causation before the trial judge at the conclusion of the trial. 

In closing submissions, the defendant’s counsel successfully argued that the deficiencies in the expert’s report meant that the claimant had failed to prove his case on the balance of probabilities. Those deficiencies had, for the first time, been properly set out in the defendant’s skeleton argument, served the afternoon before trial.

The trial judge, HHJ Truman, accepted the evidence of Mr and Mrs Griffiths, who were described as patently honest and straightforward witnesses. However, HHJ Truman dismissed Mr Griffiths’ case, discounting the expert evidence and finding that the claimant had not proven his claim. HHJ Truman was also critical of Professor Pennington’s responses to the CPR Part 35 questions.

The trial judge’s decision was overturned on appeal to the High Court. In a judgment dated 20 August 2020 ([2020] EWHC 2268 (QB)), Martin Spencer J stated that the appeal raised a fundamental question concerning the proper approach of courts towards uncontroverted evidence. 

The High Court decision was then overturned by a majority verdict of the Court of Appeal. In a judgment dated 7 October 2021 ([2021] EWCA Civ 1442; [2022] 1 WLR 973), Aspin LJ delivered the leading judgment (Nugee LJ agreeing, Bean LJ dissenting). Aspin LJ expressed that there was no strict rule preventing a court from considering the content of an expert report which complied with CPR PD 35, where it had not been challenged by contradictory evidence and where there had been no cross-examination (at [69]). 

The remaining grounds of appeal were dealt with briefly: the High Court judge had erred in law in concluding that the report complied with CPR PD 35 because it did not give a range of opinion in response to the defendant’s question; a report had to provide some reasoning in support of an expert’s conclusion; and the challenge to the contention that there was a rigid test that a judge must accept uncontroverted expert evidence if it meets the minimum standards established by CPR PD 35 was accepted. 

Nugee LJ agreed with Aspin LJ’s analysis and conclusions and added that “[u]ncontroverted evidence may be compelling, but it may not be: it may be inherently weak or unhelpful or of little weight for other reasons” (at [81]).

Bean LJ, in his strongly worded dissent, described as trite law the statement that in general, a party is required to challenge on cross-examination the evidence of any witness of the opposing party if it wishes to submit to the court that that evidence should not be accepted (as set out in Phipson on Evidence). He stated that other than in exceptional circumstances (at [94]): 

a judge is generally bound to accept the evidence of an expert if it is not controverted by other expert or factual evidence and the opposing party could have cross-examined the expert on the point but chose for tactical reasons not to do so.

 He concluded that the “courts should not allow litigation by ambush” (at [99]). 


 Appeal to the Supreme Court 

There were three principal questions raised on appeal (at [34]): 

  1. What is the scope of the rule, based on fairness, that a party should challenge by cross-examination evidence that it wishes to impugn in its submissions at the end of the trial? 
  2. In particular, does the rule extend to attacks in submissions on the reliability of a witness’s recollection and on the reasoning of an expert witness? And
  3. If the rule does so extend, was there unfairness in the way in which the trial judge conducted the trial in this case? 

Lord Hodge, delivering the single judgment of the Supreme Court, overturning the Court of Appeal decision, set out several principles of trite law in civil proceedings (at [36]): 

  1. As a generality in civil proceedings, the claimant bears the burden of proof in establishing his or her case;
  2. The role of an expert is to assist the court in relation to matters of scientific, technical or other specialised knowledge which are outside the judge’s expertise by giving evidence of fact or opinion, but the expert must not usurp the functions of the judge as the ultimate decision-maker on matters that are central to the outcome of the case. Thus, as a general rule, the judge has the task of assessing the evidence of an expert for its adequacy and persuasiveness. 
  3. English law operates an adversarial system, and the parties frame the issues for the judge to decide in their pleadings and their conduct in the trial. 
  4. In that context, it is an important part of a judge’s role to make sure that the proceedings are fair. 

He stated that “at the heart of this appeal lies the question of the requirements of a fair trial” (at [36]).

In considering the correct approach towards the scope for judicial evaluation of an expert report, Lord Hodge went on to set out how the case law had been developed over time. In doing so, he also drew attention to the most recent edition of Phipson on Evidence (20th ed (2022)) (at [42]). This states that:

In general a party is required to challenge in cross- examination the evidence of any witness of the opposing party if he wishes to submit to the court that the evidence should not be accepted on that point. The rule applies in civil cases ... In general the CPR does not alter that position. 

This rule serves the important function of giving the witness the opportunity of explaining any contradiction or alleged problem with his evidence. If a party has decided not to cross- examine on a particular important point, he will be in difficulty in submitting that the evidence should be rejected. 

(emphasis added) 

Lord Hodge was satisfied that this statement correctly summarised a “longstanding rule of general application” being “a matter of fairness of the legal proceedings as a whole” with “which practising barristers would be familiar” (at [43] and [61]).

In conclusion, Lord Hodge summarised the relevant law and principles regarding the rules of evidence (at [70]):

  1. The general rule in civil cases, as stated in Phipson, 20th ed, para 12-12, is that a party is required to challenge by cross-examination the evidence of any witness of the opposing party on a material point which he or she wishes to submit to the court should not be accepted. That rule extends to both witnesses as to fact and expert witnesses. 
  2.  In an adversarial system of justice, the purpose of the rule is to make sure that the trial is fair.
  3.  The rationale of the rule, i.e. preserving the fairness of the trial, includes fairness to the party who has adduced the evidence of the impugned witness. 
  4. Maintaining the fairness of the trial includes fairness to the witness whose evidence is being impugned, whether on the basis of dishonesty, inaccuracy or other inadequacy. An expert witness, in particular, may have a strong professional interest in maintaining his or her reputation from a challenge of inaccuracy or inadequacy as well as from a challenge to the expert’s honesty. 
  5. Maintaining such fairness also includes enabling the judge to make a proper assessment of all the evidence to achieve justice in the cause. The rule is directed to the integrity of the court process itself. 
  6. Cross-examination gives the witness the opportunity to explain or clarify his or her evidence. That opportunity is particularly important when the opposing party intends to accuse the witness of dishonesty, but there is no principled basis for confining the rule to cases of dishonesty. 
  7. The rule should not be applied rigidly. It is not an inflexible rule and there is bound to be some relaxation of the rule, as the current edition of Phipson recognises in para 12.12 in sub-paragraphs which follow those which I have quoted in para 42 above. Its application depends upon the circumstances of the case as the criterion is the overall fairness of the trial. Thus, where it would be disproportionate to cross-examine at length or where, as in Chen v Ng, the trial judge has set a limit on the time for cross-examination, those circumstances would be relevant considerations in the court’s decision on the application of the rule. 
  8. There are also circumstances in which the rule may not apply: see paras 61-68 above for examples of such circumstances. 

(emphasis added)

The (non-exhaustive) circumstances in which the rule may not apply, were set out as follows:

  1. First, where the matter to which the challenge was directed was collateral or insignificant [61];
  2. Secondly, where the evidence of fact is manifestly incredible and an opportunity to explain it would make no difference [62];
  3. Thirdly, where there is a bold assertion of opinion in an expert’s report without any reasoning to support it (a situation which is termed “bare ipse dixit”). Importantly, this is not the same as a situation where an expert’s reasoning appears inadequate and is open to criticism for that reason [63]
  4. Fourthly, where there is an obvious mistake of fact on the face of an expert report or the report was ex facie illogical or inherently inconsistent [64];
  5. Fifthly, where the witnesses’ evidence of the facts may be contrary to the basis on which the expert expressed his or her view in the expert report [66]
  6. Sixthly, where an expert has been given a sufficient opportunity to respond to criticism of, or otherwise clarify their report. For example, if an expert faces focused questions in the written CPR Pt 35.6 questions of the opposing party and fails to answer them satisfactorily, a court may conclude that the expert has been given a sufficient opportunity to explain the report which negates the need for further challenge on cross-examination [67]; and
  7. Seventhly, where there is a failure to comply with the requirements of CPR PD 35. However, a party seeking to rely on such a failure would be wise to seek the directions of the trial judge before doing so, as much will depend upon the seriousness of the failure [68]


Application of the law to the facts in Tui v Griffiths

The Court found that when applying those principles of law to the facts of Tui v Griffiths, regard needed to be had to the following (at [71]):

  1. TUI in its defence put Mr Griffiths to proof of his claim; 
  2. TUI chose not to lodge the report of an expert microbiologist, which it obtained, which may have put forward a different case on causation to that of Professor Pennington; 
  3. TUI failed to lodge the report of their expert gastroenterologist in a timely manner and called no witnesses as to fact; 
  4. The CPR Part 35.6 questions were not clearly focused on the matters which were the object of counsel’s submissions and did not put Professor Pennington on notice of those criticisms;
  5. TUI chose not to request Professor Pennington be available for cross-examination; 
  6. TUI’s challenge to his evidence was not intimated to Mr Griffiths’ legal team until the submission of its skeleton arguments on the eve of the trial, by which time it would have been too late for them to seek to have him attend to give evidence;
  7. Professor Pennington’s report related to causation, a central issue in the case; 
  8. Whilst Professor Pennington’s report was terse and left many relevant questions unanswered, it was far from a bare ipse dixit;
  9. Professor Pennington had explained an important part of his reasoning in his answers to the CPR Part 35 questions and had made a simple assessment of the likely cause of the illness and whilst that reasoning was at a high level of generality, it was not irrational and may have been proportionate in the circumstances of the claim; and
  10. There was no basis for concluding that Professor Pennington would not have explained his reasoning more clearly if challenged on cross-examination.

Lord Hodge concluded that none of the exceptions identified applied to the expert evidence of Professor Pennington and in the “absence of a proper challenge on cross-examination it was not fair for TUI to advance the detailed criticisms of Professor Pennington’s report in its submissions or for the trial judge to accept those submissions” (at [75]). Both the trial judge and the majority of the Court of Appeal had therefore “erred in law in a significant way”. The Supreme Court agreed with Bean LJ’s dissenting judgment that Mr Griffiths did not have a fair trial (at [76]). 

Lord Hodge also rejected the distinction put forward by the Court of Appeal that they had not found that Professor Pennington’s report was wrong, but that it did not establish Mr Griffith’s case on causation. This was, as termed by Bean LJ, “hair-splitting”, given that the trial judge had rejected Professor Pennington’s conclusions on causation (at [77]). 

The Court went on to find that, on the evidence, Mr Griffiths had established his case on the balance of probabilities (at [78]). 



Impact of the judgment 

The Supreme Court went on to briefly consider the impact that the judgment may have on low-value holiday sickness claims. Lod Hodge stated that (at [81]):


The conclusion I have reached does not mean that in most cases of modest value when a claimant presents an inadequately reasoned expert report, a defendant will inevitably have to obtain a detailed expert report and require a claimant’s expert to attend for cross-examination. A defendant may be able to adopt more economic ways of testing the expert’s evidence. It is important and consistent with the ethos of the CPR that there be a proportionate use of resources in the pursuit and defence of such claims. A defendant can ask focused CPR Pt 35.6 questions which articulate clearly the challenge or challenges on which the defendant wishes to make and give the expert the opportunity to explain his or her evidence in response to those challenges, thereby obviating the need to seek the expert’s attendance for cross- examination. […]

Where the defendant has expert advice, a meeting of experts to discuss their positions can lead to a joint report restricting the issues in dispute. In any event, a focused cross-examination making the challenge and giving the expert the opportunity to explain his or her report and CPR Pt 35.6 answers need not be long. 


Overall, the judgment appears to provide a useful clarification on the requirements of a fair trial in relation to “uncontroverted” expert evidence.

In my opinion, the important considerations for parties to remember moving forward are as follows: 

  • There is no difference between a judge finding that an expert report is wrong and finding that a claimant doesn’t come up to proof because the conclusions of an expert have been dismissed; 
  • If a party wishes to challenge a witness (whether lay or expert) on an issue which is central to a case, that party must give that witness an opportunity to respond to that challenge;
  • That opportunity may be through cross-examination or Part 35 questions, but any Part 35 questions ought to directly address any criticisms that will be made in submissions; 
  • If expert evidence is not challenged, unless one of the exceptions set out above applies, the evidence must be accepted by the court for there to be a fair trial. 

The (non-exhaustive) exceptions set out by Lord Hodge cover a range of scenarios. It appears that the most relevant exceptions for everyday practice, to which particular attention should be paid, are where the factual basis upon which a report is written is inaccurate and where a report could be classified as “bare ipse dixit” (a bold assertion without any reasoning to support it). 

In the sphere of personal injury and clinical negligence claims, an interesting question may arise where a party is seeking to undermine the factual basis of a report, such as an expert not being told about a claimant’s relevant medical history or relevant previous accidents, where such history is clearly set out in medical records to which an expert has relied upon. 

The judgment is likely to have a significant impact on low-value and fixed cost claims, where expert reports are subject to fixed disbursement fees and are often brief. The potential impact in these cases is especially heightened, given that defendants routinely do not ask focussed (or any) Part 35 questions of claimants’ experts, often do not seek – or are not given permission – to adduce their own expert reports, and such experts are frequently not called to give evidence at trial. 

However, it is clear for now from the findings of the Supreme Court in Tui v Griffiths, that it will not be enough for a defendant to merely highlight deficiencies in a report in closing submissions if those deficiencies are not sufficient to bring such evidence within the above exceptions. For a court to allow otherwise would result in an unfair trial.