Challenging expert evidence: TUI UK Ltd (Respondent) v Griffiths (Appellant) [2023] UKSC 48

The facts

Mr Griffiths suffered a serious stomach upset while on an inclusive package holiday booked with TUI, which left him with long term problems. At trial, he relied on the evidence of an expert who opined that, on the balance of probabilities, the food and drink served at the hotel was the cause of the stomach upset. 

TUI had missed the deadline to rely on its expert report and the court refused its application for relief from sanctions so TUI went to trial without the support of any expert evidence. TUI then did not seek to have the Claimant's expert attend trial to be cross-examined such that his expert evidence was, on paper, not contested.

However, in its skeleton argument and closing submissions, TUI's Counsel argued that deficiencies in the expert report meant that the Claimant had failed to prove his case. The trial judge was convinced and dismissed the claim.

After a series of appeals, the Supreme Court considered the extent to which the trial judge was entitled to this finding when the expert had given uncontroverted evidence that was not illogical, incoherent, nor based on any misunderstanding of the facts, but criticised as being incomplete in its explanations or consideration of other possible causes.

The judgment

The main issues considered by the Supreme Court were:

(i) 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? 

(ii) 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 

(iii) if the rule does so extend, was there unfairness in the way in which the trial judge conducted the trial in this case?

There is a clear long-standing rule 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.

The Court considered a number of exceptions to this rule, including:

• that the matter challenged is insignificant so fairness does not require there to be an opportunity to explain;
• the evidence may be manifestly incredible;
• there may be a bold assertion of an opinion in an expert's report without any reasoning to support it;
• there may be an obvious mistake on the face of an expert report;
• the evidence of fact may be contrary to the basis on which the expert expressed their view; or
• an expert has been given sufficient opportunity to respond to criticism of, or otherwise clarify their report, such as through written questions.

None of the above exceptions applied to the present case. The Supreme Court found for Mr Griffiths.

Comment

Expert evidence can make or break a case. A party can choose to challenge its opponent's expert evidence in a number of ways, including by relying on its own expert evidence, putting written questions to the expert under CPR 35.6, or requiring the expert to attend trial to be cross-examined.

Parties will need to take great care before deciding not to take any of these opportunities or they might end up with an upset stomach of their own.