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Challenging expert evidence

The appeal decision of the Supreme Court was handed down towards the end of 2023 in the case of TUI UK Ltd v Griffiths [2023] UKSC 48, providing important clarification of when a court can evaluate and reject an "uncontroverted" expert's report.

Mr Griffith's claim arose from a bout of acute gastroenteritis he suffered whilst on a holiday in Turkey. The claimant had purchased the said all-inclusive holiday from the defendant and alleged that during his holiday all his meals had been consumed at the hotel save for 1. He therefore brought a claim asserting that his condition had been caused by contaminated food or drink supplied by the defendant during his stay, or alternatively the unhygienic state of the hotel swimming pool. He obtained a pre-litigation medical report from a consultant gastroenterologist which stated that on the balance of probabilities the claimant's illness was the result of the poor hygiene standards within the hotel. When the case litigated the claimant also obtained a report from a microbiologist to address causation.

Liability was denied and the claimant put to proof in respect of causation. Despite receiving permission for their own medical evidence, the Defendant did not serve any reports in time to challenge the claimant's evidence. The court took the view that that the claimant's medical evidence was not illogical, incoherent or inconsistent, based on any misunderstanding of the facts or based on unrealistic assumptions, but it was criticised as being incomplete in its explanations and for its failure to expressly discount on the balance of probabilities other possibles causes of the claimant's illness.

The claimant's medical experts were not called to court to give oral evidence and so their evidence was limited to the paper reports. The only expert evidence relied upon for causation was in the uncontroverted report of the claimant's microbiologist. The defendant had put Part 35 questions to him and then raised specific criticisms of his findings in their skeleton argument at trial, these being repeated in the submissions at trial. Specifically they raised the failure of the expert to discount the occurrence of 2 separate infections and that a meal out in Turkey had caused the second, that he had given no explanation as to why he concluded that the illness was caused by the food at the hotel, that he had failed to consider the food consumed at the airport or the meal in town and exclude them as causes, he failed to comment on possible breaches of health and hygiene procedures and had failed to discount the methods of transmission of the illness which were not related to food. At first instance the trial judge also noted that the expert had failed to explain why the adenovirus and rotavirus found in the claimant on testing had no effect on his health and were discounted as a cause.

At first instance the trial judge held that the claimant had not proven his case and dismissed the claim on the basis that the medical reports did not comply with CPR 35 for failing to supply a range of opinion and failing to supply sufficient information to be able to set out a clear train go logic between the facts and the diagnosis.

On appeal the questions to be determined were whether a court is obliged to accept an expert's uncontroversial opinion even if that opinion could be characterised as an ipse dixit or mere assertion; and if not what were the circumstances in which a court could be justified in rejecting such evidence.

The outcome of this decision was flipped several times on appeal until the matter appeared before the Supreme Court for a final determination.

The Supreme Court advised that an expert should set out his reasoning in the report pursuant to paragraph 62 of the Guidance for the Instruction of Experts in Civil Claims 2014 which CPR PD 35 requires them to be aware of. The general rule in civil cases however 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 to fact and experts. It is not an inflexible rule however and there is bound to be some relaxation of the rule dependant on circumstances. The examples quoted were:

1. The matter to which the challenge is directed is collateral or insignificant
2. The evidence of fact is manifestly incredible and an opportunity to cross examine would make no difference.
3. A bold assertion of opinion in an experts report without any reasoning to support it.
4. Obvious mistake on the facts of the expert report.
5. Witnesses evidence of fact may be contrary to the basis on which the expert expressed his views in the report.
6. An expert has been given a sufficient opportunity to respond to criticism of, or otherwise clarify his report i.e. Via Part 35 questions.
7. Failure to comply with the requirements of CPR 35

Here the Supreme Court noted that TUI chose not to serve their own microbiologist report. They failed to serve a report from their own gastroenterologist in a timely manner and called no witnesses of fact. The Part 35 questions put to the expert were not clearly focussed on the criticism then raised at trial and did not put the expert on notice of the same. They did not request the expert to attend for cross examination and the points were not intimated to the claimant's legal team until the submission of skeleton arguments. The trial judge accepted the entirety of the claimant's lay witness evidence so there was no difference of facts. The expert's report was terse and could, and should, have included more expansive reasoning, but it was far from a bare ipse dixit. None of the above exceptions therefore applied to the evidence. Given the factual findings of the trial judge of poor hygiene standards, and the conclusions of the expert, the claimant was found to have established his case on the balance of probabilities.

Forbes Comment

The outcome of this case confirms that if you wish to challenge a claimant's expert report, you must consider the steps necessary to do so before trial. Whilst the court is not prevented from discounting an experts' findings if they are decided on facts not established at trial or are conclusions that cannot be supported at all, in most scenarios a defendant will need to take further steps to undermine the same. This will be done with their own expert evidence if the case warrants the same, by Part 35 questions addressing the specific criticism or by seeking to call the expert for cross examination. In most cases the most costs effective method would appear to be the use of questions. A court is not however entitled to ignore an expert report at trial as a result of criticisms raised in submissions only unless there is a justification for the same, and it would not prevent a fair trial. If you have any queries about the use of expert evidence please do not hesitate to contact us.

For more information contact Claire Opacic in our Insurance department via email or phone on 01618308817. Alternatively send any question through to Forbes Solicitors via our online Contact Form.

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