Managing director, David Stothard, considers lessons from the recent TUI UK Ltd v Griffiths case in our monthly bite-size article supporting expert’s continuing professional development.

It is a very rare thing for a case about expert evidence to make its way to the highest court in the land, but in TUI UK Ltd v Griffiths (2023) the arguments over the evidence of the eminent expert microbiologist, Professor Hugh Pennington, resulted in just that.

I should be clear about one point from the outset: none of the appeal courts which dealt with this case felt that Professor Pennington’s report was a good one. However, rather than the technical legal points which were dealt with in the case, I am interested in trying to find the lessons for expert witnesses about what went wrong and how they could avoid a similar journey.


To understand what happened it is important to have some details of the background to the case.

The Griffiths family went on an all-inclusive package holiday to Turkey with TUI. Whilst there, Mr Griffiths got food poisoning to the extent that he was hospitalised and suffered long-term consequences afterwards.

The claim was worth about £30,000 in damages. His solicitors prepared the case in the usual way, obtaining expert evidence on condition and prognosis from an expert gastroenterologist and relying on Professor Pennington to establish causation (the link between the negligent events and the injury).

The defence from TUI followed the usual form too. It denied liability, putting Mr Griffiths to prove that his illness had been caused by the consumption of substandard food or drink in the hotel, rather than elsewhere. He had eaten one meal at the airport before departure and one meal in the local town, otherwise he had eaten only at the hotel during his fifteen-night holiday.

Common problems in such cases are conflicting evidence about food hygiene standards in the hotel and the absence of analysis of a contemporaneous stool sample to provide sufficient microbiological evidence to establish causation. Fortunately for Mr Griffiths, the latter was available from the lab results from the Turkish hospital. He was also fortunate that TUI was unable to call its lay witnesses on the issue of the hotel’s food hygiene standards or its expert evidence. The consequence was that the judge in the county court only had Mr and Mrs Griffith’s evidence at trial and found no reason not to accept what they said.

Attacks on the expert witness report

In the absence of its own expert evidence, TUI tried to attack Professor Pennington’s evidence to demonstrate that it did not establish the causative link between the substandard food hygiene at the hotel and gastroenteritis suffered. His initial report was short and his answers to TUI’s CPR 35.6 questions could be described as terse. However, he maintained his position that causation was established on the available test results and evidence.

Cases of this type require permission from the court for an expert to be called to give evidence at trial. Decisions on whether to call an expert witness are tactical, but can be influenced by the value of the case. It seems that it was accepted that this case did not warrant the attendance of the expert witnesses. TUI did not indicate that it wished to cross examine Professor Pennington and there was no opportunity for TUI’s legal team to do so.

That left TUI in the position that it was not convinced that Professor Pennington’s report went far enough to prove causation, but without any evidential basis to challenge it. It fell back on seeking to point out the weaknesses which it had identified in his evidence. The judge at first instance accepted those arguments and found that despite the uncontroverted evidence from Professor Pennington, his report and answers to the CPR 35.6 questions were not sufficient to establish causation, so the claim failed.

On appeal in the High Court, that decision was overturned. It was then re-instated by the Court of Appeal and ultimately overturned by the Supreme Court again.

To deal briefly with the legal point, the Supreme Court found that 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, and so a fair trial had not taken place.

What does this mean for expert witnesses?

As an expert witness you will never want to be in this position, nor would you want to put your instructing party or the court in this situation.

Cases of low or modest value almost always come with limitations on the fees available to expert witnesses to produce their evidence. It is completely understandable that experts wish to keep their reports as short as possible in the circumstances. In fact, this is welcomed by the courts. As an expert witness in such a case, you may have a clear view about the issues and seek to express that as succinctly as possible. That must not be at the expense of giving sufficient reasoning to support the conclusion reached. It is rarely appropriate to assume that one’s reasoning is implicit, and it is preferrable to err on the side of presenting it expressly.

In this case, the court found that Professor Pennington’s report left many questions unanswered, but that his replies to the Part 35.6 questions from TUI showed sufficient of his reasoning so that what was said was not a bare assertion of his conclusion. It therefore met the legal standard required. But, it was clearly far too close for comfort for Mr Griffiths’ lawyers and provoked critical responses from the members of the judiciary who heard the case at each level.

Practice Direction

The Practice Direction to CPR 35 states, at section 3.2(6), that where there is a range of opinion on the matters to be dealt with, the expert should summarise the range of opinions and give reasons for their own opinion. It is always important to address this issue when preparing a report to help the court understand how you have considered the options and reached your conclusion. It also enables you to be clear that you understand your role in assisting the court to reach a decision, but not usurping the judge’s role in deciding the facts and applying the law.

As an expert in such a case where expert evidence is limited, you should expect to receive CPR 35.6 questions from the ‘other side’. Such questions are an ordinary part of the litigation process rather than an annoyance. They are equivalent to a written cross examination of your evidence and should be treated in the same way as if the questions were being put to you in the witness box.

It is interesting to note that the Supreme Court rejected TUI’s concern that the impact of the decision would be to require defendants always to obtain their own expert evidence and require the claimant’s expert to attend trial for cross examination. Instead, the court expressly endorsed asking focused CPR 35.6 questions which clearly articulate the challenges which that party wishes to make and gives the expert the opportunity to explain their evidence in response to those. In this case, TUI’s questions did not give adequate notice of the challenges it ultimately made.

As a result of this decision, expert witnesses can expect their instructing solicitors to be more focussed on ensuring that your report meets the standard required and that the ‘other side’ will be encouraged to explore any perceived weaknesses in your evidence. Spending a little more time in the drafting process may save considerable toing and froing later, which is rarely adequately financially compensated.

Further insights

In preparing this piece I have been greatly assisted by the EWI’s webinar ‘Uncontroverted evidence in the courts’, presented by Lord Hodge, Deputy President of the Supreme Court, who gave the judgment of the court in this case; and Deka Chambers webinar on the decision which included insights from Mr Griffiths’ solicitor, Jatinder Paul. Both recordings are available to view through the respective website links.

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