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Challenging times for experts in the Supreme Court

30 November 2023

TUI (UK) Ltd v Griffiths [2023] UKSC 48 - The UK Supreme Court has handed down judgment in a case which, although concerning a personal injury claim, and set against the backdrop of the civil procedure rules which apply only in England & Wales, will be of general interest across all types of litigation, as it concerns the treatment of unchallenged expert witness evidence. The judgement adds to a body of caselaw that has been developing over recent years in relation to how expert evidence should be dealt with by the courts. The Supreme Court set out, in the Scottish case of Kennedy v Cordia (Services) LLP [2016] UKSC 6, the criteria for determining the admissibility of expert evidence. Here, it considers the circumstances in which the court may (and may not) accept unchallenged expert witness evidence.

The background is that the claimant, Mr Griffiths, raised proceedings against TUI seeking damages for gastric illness which he claimed he suffered as a result of consuming contaminated food while on holiday. He had booked a package holiday through the Defendant company TUI, staying at an all-inclusive hotel in Turkey.   The claim fell within the scope of the Package Travel, Package Holiday and Package Tour Regulations 1992.

Claire White

Claire White

TUI lodged a defence in which it denied that the illness had been caused by the consumption of food or drink in the hotel, and put Mr Griffiths to proof as to the cause of his illness.

Mr Griffiths relied upon expert reports, from a gastroenterologist and from a microbiologist, Professor Hugh Pennington. Both parties were given permission under the lower court’s case management process to rely on expert evidence from a gastroenterologist and a microbiologist.

Surprisingly, despite this, TUI went to trial without the support of any expert evidence of their own. They did not seek to have Professor Pennington attend the trial for cross-examination in person, with the result that his evidence was accepted on paper in the form of his written report.  His expert evidence was therefore uncontroverted in the sense that it was not in conflict with any other evidence led at the trial and was not subjected to challenge by cross-examination. 

At the close of the trial, in submissions, Counsel for TUI made specific criticisms of Professor Pennington’s evidence relating to, among other things, a lack of proper reasoning and a failure to fully discount other possible causes of the illness,  and invited the trial judge to find that the claimant had failed to prove his case. The trial judge found in favour of TUI, holding that the criticisms of the report by Professor Pennington were well founded and that as a result, the claimant’s case had not been proved.

The claimant appealed to the Court of Appeal. In a majority judgement, it rejected the appeal, a decision which was partly based on its assessment that the requirement to cross examine an expert only applied where the expert was being accused of dishonesty.

The claimant appealed to the Supreme Court. In the unanimous judgement, TUI UK Ltd (Respondent) v Griffiths (Appellant) - The Supreme Court delivered by Lord Hodge, the court upheld the appeal, identifying a set of seven principles regarding the requirement to cross examine an expert witness:

1. The general rule in civil cases 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.  An expert witness may have a strong professional interest in maintaining his or her reputation from a challenge of inaccuracy or inadequacy as well a challenge to their 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 the rule is not limited to accusations 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 it.   Its application depends upon the circumstances of the case as the criterion is the overall fairness of the trial.  There are circumstances in which the rule may not apply, such as where the criticism of the expert is on a collateral matter not likely to be central to the outcome of the case. 

The court held that:

o In the absence of a proper challenge on cross-examination it was not fair for TUI to advance criticisms of Professor Pennington’s report in its submissions or for the trial judge to accept those submissions.

o Both the trial judge and the majority of the Court of Appeal had erred in law in a significant way. The trial judge did not consider the effect on the fairness of the trial of TUI’s failure to cross-examine Professor Pennington.

o The majority of the Court of Appeal did consider this, but they erred in limiting the scope of the rule to challenges to the honesty of a witness.

As a result of these failings, Mr Griffiths had not received a fair trial. The court also determined that on the basis of the evidence before it, he had proved his case on the balance of probabilities. The appeal was therefore allowed.

The court’s decision to uphold the appeal perhaps comes as no surprise and might be viewed as a welcome re-statement and reminder of general principles relating to expert evidence. Some of the issues in this case related to the specific practice rules in operation in England & Wales. However, litigants elsewhere, and indeed in other types of litigation where expert evidence is required, should take care to ensure that when they make tactical decisions regarding expert evidence, in preparation for trial, they preserve their ability to properly test the expert witness of their opponents, if that is something they wish to do.

Failure to properly plan and execute this important preparatory work may result in an inability to challenge the evidence in any meaningful way. Once in court, it may be too late to retrieve the situation.

Claire White, Partner: / 0141 221 8012

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