A Supreme Court decision handed down last week establishes that the general rule in civil cases is that a party who submits that the court should not accept an opponent’s witness evidence on a material point must challenge that evidence by cross-examination – whether it is factual or expert evidence, and regardless of whether the challenge is based on dishonesty or some other defect. The trial judge’s acceptance of criticisms of the claimant’s uncontroverted expert report in this case, in the absence of a proper challenge on cross-examination, therefore rendered the trial unfair: TUI (UK) Ltd v Griffiths [2023] UKSC 48.

The decision overturns the Court of Appeal’s judgment (considered here) which found that the court was not bound to accept an expert’s uncontroverted evidence, and it was open to a party to challenge the opponent’s expert evidence for the first time in closing submissions. The Court of Appeal had considered the so-called principle in Browne v Dunn (1893) 6 R 67 HL to be irrelevant to this case as it applied only to challenges to a witness’s credibility or the truth of their evidence. The Supreme Court disagreed: while that case and many others which applied the principle were concerned with challenges to honesty, there was no rational basis for confining the principle to such cases.

The Supreme Court’s decision emphasises that, in our adversarial system of justice, while the judge is the ultimate decision-maker and must assess the expert evidence for its adequacy and persuasiveness, it is for the parties to frame the issues for the judge to decide. In that context, it is an important part of the judge’s role to ensure that the proceedings are fair, and fairness requires that a witness be given the opportunity to explain an alleged defect in their evidence on a material point.

The decision makes it clear that the rule should be applied flexibly, and that it may not apply in all circumstances. There may be no need to challenge an expert’s evidence, for example, where it is a mere assertion of opinion unsupported by reasoning, or is obviously illogical or contrary to the factual evidence on which it was based. And there may be ways to enable the expert to respond to criticism without having to cross-examine them, such as by putting specific written questions to the expert under CPR 35.6.

However, the clear takeaway from the decision is that, in most cases, parties who wish to persuade the court that their opponents’ witness evidence should not be accepted in a material respect would be well advised to ensure the witness has an opportunity to respond to the relevant challenge in cross-examination.


The claimant brought a claim against the defendant travel company in respect of gastric illness he alleged was caused by contaminated food or drink served at the hotel he had stayed at when on an all-inclusive holiday to Turkey.

The claimant’s case on causation was supported by an expert report from a microbiologist, Professor Pennington. The defendant did not rely on any expert evidence and did not seek to cross-examine Professor Pennington, but put a number of written questions to him under CPR 35.6, which he answered. The defendant’s skeleton argument served on the afternoon before trial set out a number of specific criticisms of his evidence, which formed the basis of the defendant’s submissions at trial.

The trial judge dismissed the claim on the basis that causation had not been proved, having largely accepted the defendant’s criticisms of Professor Pennington’s evidence. She stated that the report did not provide her with sufficient information to be able to say that there was a clear train of logic to conclude that the hotel food was the more likely cause of the claimant’s illness, rather than a pre-flight meal or a meal in the local town.

On appeal, the High Court (Martin Spencer J) overturned that decision and entered judgment for the claimant on the basis that the court had been bound to accept Professor Pennington’s evidence. The judge considered that the court was not entitled to subject an uncontroverted expert report to the same kind of analysis and critique as if it was evaluating a contested report, where it has to assess the weight to be given to the report as compared to the controverting factual or expert evidence. In his view, where a report is uncontroverted, the court need only decide whether it fulfils certain minimum standards in order to be accepted, ie the requirements for the form and content of an expert report set out in CPR PD 35.

A majority of the Court of Appeal (Asplin and Nugee LJJ) allowed the defendant’s further appeal and reinstated the order of the trial judge. It held that there is no strict rule that prevents the court from considering the content of an expert’s report which complies with CPR PD 35 where it has not been challenged by contradictory evidence and where there is no cross-examination.

Bean LJ delivered a dissenting judgment expressing profound disagreement with the majority’s decision. He gave his view that, other than in exceptional circumstances, a judge is generally bound to accept expert evidence if “it is not controverted by other expert or factual evidence and the opposing party could have cross-examined the expert on the point but chose for tactical reasons not to do so” (emphasis in original).


The Supreme Court unanimously allowed the claimant’s appeal. Lord Hodge gave the court’s judgment, with which Lord Lloyd-Jones, Lord Briggs, Lord Burrows and Lord Stephens agreed.

Lord Hodge began his analysis of the law with a number of general principles, including that the role of an expert is to assist the court in relation to matters of scientific, technical or other specialised knowledge which are outside the judge’s expertise, but the judge is the ultimate decision-maker and must assess the expert’s evidence for its adequacy and persuasiveness. Accordingly, the quality of an expert’s reasoning is of prime importance. Lord Hodge disagreed with Martin Spencer J’s view, as expressed in this case, that an expert was not required to set out their reasoning. This requirement is set out in the Guidance for the Instruction of Civil Claims 2014, which is referred to in para.3.2(9) of CPR PD 35.

Lord Hodge further noted that, in our adversarial system, the parties frame the issues for the judge to decide, based on the evidence the parties adduce. In that context, it is an important part of the judge’s role to make sure that the proceedings are fair.

Against that background, after a detailed examination of the authorities, the court held that 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 that it submits should not be accepted. That rule extends to both witnesses as to fact and expert witnesses. The court endorsed the following statement in Phipson on Evidence (20th ed, para 12-12):

“In general a party is required to challenge in crossexamination the evidence of any witness of the opposing party if he wishes to submit to the court that the evidence should not be accepted on that point. The rule applies in civil cases … In general the CPR does not alter that position.

This rule serves the important function of giving the witness the opportunity of explaining any contradiction or alleged problem with his evidence. If a party has decided not to crossexamine on a particular important point, he will be in difficulty in submitting that the evidence should be rejected.”

The purpose of the rule is to make sure that the trial is fair. This includes fairness to the party who has adduced the evidence, as well as to the witness, whether the challenge is based on dishonesty, inaccuracy or other inadequacy. An expert witness, in particular, may have a strong professional interest in maintaining their reputation against a challenge of inaccuracy or inadequacy as well as honesty.

The rule is also directed to the integrity of the court process itself, as it enables the judge to make a proper assessment of all the evidence to achieve justice. Cross-examination gives the witness the opportunity to explain or clarify their evidence, which is particularly important when there is an accusation of dishonesty, but the rule is not confined to such cases.

The rule should not be applied rigidly. Its application depends on the circumstances of the case as the criterion is the overall fairness of the trial. For example, where it would be disproportionate to cross-examine at length or where the trial judge has set a limit on the time for cross-examination, those would be relevant considerations.

There are also circumstances in which the rule may not apply. Lord Hodge listed several, on a non-exhaustive basis, including:

  • Where the challenge is directed to a collateral or insignificant matter and fairness to the witness does not require there to be an opportunity to answer or explain.
  • Where evidence of fact is manifestly incredible and an opportunity to explain on cross-examination would make no difference.
  • Where there is a mere assertion of opinion in an expert’s report without any reasoning to support it, sometimes referred to as bare ipse dixit – but that does not include reasoning which appears inadequate and is open to criticism for that reason.
  • Where there is an obvious mistake on the face of an expert report, or it is obviously illogical or inherently inconsistent.
  • Where the witnesses’ evidence of the facts is contrary to the basis on which the expert expressed their view.
  • Where an expert has been given a sufficient opportunity to respond to criticism of, or otherwise clarify, their report – for example by answering questions put to the expert under CPR 35.6.
  • Where an expert has failed to comply with the requirements of CPR PD 35, though much would depend on the seriousness of the failure and so a party seeking to rely on such a failure would be wise to first seek directions from the trial judge.

On the facts of the present case, the Supreme Court concluded that it was not fair for the judge to accept the defendant’s criticisms of Professor Pennington’s report in the absence of a proper challenge on cross-examination. Although the report should have included more expansive reasoning, it was far from a bare ipse dixit. In the context of a relatively low-value claim, Professor Pennington may have thought his full reasoning was implicit, he had explained an important part of his reasoning in his answers to the written questions, and there was no basis for concluding that he would not have explained his reasoning more clearly if challenged on cross-examination.

That meant that the claimant did not have a fair trial, and it was for the Supreme Court to make its own assessment of the evidence. Based on that evidence, including Professor Pennington’s uncontroverted evidence, the claimant had established his case on the balance of probabilities.