TUI appealed to the Court of Appeal, where the court found in its favour 2-1.
The majority (Asplin LJ and Nugee LJ) held that the authorities did not support the "bright line" approach adopted by the High Court to the treatment of controverted and uncontroverted expert evidence: there was no rule that an uncontroverted expert's report which complied with CPR PD 35 cannot be rejected by the judge. Instead, it required a more nuanced approach, and all depended on the circumstances of the case, the nature of the report itself and the purposes for which it was being used in the claim.
However, the court noted that, where the evidence was that of a joint expert, which went to the relevant issues and contained logical conclusions, it was very hard to see that it could be successfully challenged. The same had to be true if there were two experts who had produced coherent reports covering the relevant issues and who were agreed. Only rarely should expert evidence be rejected in those circumstances and cogent reasons should be given.
The majority also found that, although CPR PD 35 did not state expressly that reasons were necessary in an expert's report, save where there was a range of opinion, it was clear from previous cases and as a matter of common sense that, if the court was to be satisfied as to the conclusion reached, or in a case like this one, that the evidence was sufficient to enable the claimant to satisfy the burden of proof in relation to causation, some chain of reasoning supporting the conclusion was necessary, even if short.
Mr Griffiths argued on appeal that TUI should not have been allowed to challenge Professor Pennington's report only in closing submissions, and that instead, if a party wished to criticise an expert's reasoning, they should avail themselves of all the means available under the CPR and either put in contrary evidence and/or put the points to the expert in cross-examination. In short, he contended that a party should not be allowed to sidestep those procedures, and in particular, sidestep cross examination, in order to avoid answers they do not want to hear. The majority disagreed. In their view, there was nothing inherently unfair in seeking to challenge expert evidence in closing submissions, even where contrary evidence had not been adduced and the expert had not been cross-examined. Provided an expert's veracity was not being challenged, a party could reserve its criticisms of a report until closing submissions if it wished. A defendant was entitled to submit that the case or an essential element of it had not been proved to the required standard, and could not be prevented from doing so because some of the evidence was contained in an uncontroverted report.
Consequently, the majority concluded that, even though TUI had not called any expert evidence of its own, or required Professor Pennington to attend for cross-examination, counsel for TUI was not precluded from making submissions as to the inadequacy of the reasoning in his report, and the first instance judge was not only entitled but right to examine that reasoning to see what weight to ascribe to his opinion, and whether the case had been proved, and to conclude that the evidence was insufficient to satisfy the burden of proof.