Limits on Experts’ Opinions

A recent English High Court ruling highlighted the importance of expert impartiality in legal cases. The Court dismissed an appeal, criticising the defendant’s expert for not reconsidering conclusions after hearing key evidence. The case underscores the need for experts to remain objective and open to all evidence received. Our Commercial Disputes team explores the decision.

An English High Court case recently dismissed an appeal by a defendant where the trial judge had preferred the evidence of the claimant’s expert. The trial judge was expressly critical of the defendant’s expert. The criticism was due to the expert’s failure to re-evaluate his conclusions after hearing factual evidence. It transpired that the expert did not reconsider his conclusions because he did not believe the claimant.[1]

This undermined the evidence the expert provided. Since the evidence did not consider the possibility that the Court might believe the claimant's account, it was ultimately of no help to the Court. The decision emphasises that an expert’s opinion should be open to potential findings that the Court may make. This is because, ultimately, the Court is the final decision-making authority in any litigation.

Background

The case came before the High Court as an appeal arising out of a personal injury action. The claimant worked for the defendant and sought damages for injuries allegedly suffered by breathing a noxious chemical while at work.

Following a trial on causation and damages, the trial judge made an order in the claimant’s favour. The judge awarded him general damages and made directions regarding the delivery of evidence regarding special damages. The defendant sought permission to appeal on five grounds. However, permission was granted concerning two only and the others were not pursued. Relevant to the Court’s consideration of the appeal was the evidence given at the trial. In ultimately dismissing the appeal on both grounds raised, Mr Justice Knowles quoted extensively from the transcript of the hearing. He paid particular attention to the trial judge’s ruling and specifically cited the trial judge’s comments on the approach adopted by the defendant’s expert.

Analysis

In considering the defendant’s expert’s approach to the case, the trial judge noted that each side’s expert had reviewed the relevant medical records. However, he also highlighted that the defendant’s expert had reviewed both the pleadings and the claimant’s witness statement. As a result, the expert was familiar with the assertions in the defendant’s defence and even referenced it in his report.

The trial judge further noted that the defendant’s expert had been in court and had “listened to the evidence of fact which emerged as to the detail of the incident”. This included the evidence of the claimant, whose evidence the trial judge found ‘truthful’ and ‘accurate’, and in whom he expressed confidence. However, despite the defendant’s expert having also heard that evidence, “this did not affect his conclusion.” This the trial judge described as “somewhat surprising”.

Both experts agreed that the duration of the exposure and concentration of vapour were relevant to the consequences. However, even though there was no dispute between the factual witnesses as to those two issues, the defendant’s expert did not re-evaluate his conclusions. The trial judge went on to set out why:

“The reason became apparent within the first few minutes of cross-examination: [the defendant’s expert] readily accepted that integral to his reasoning was that he did not believe [the claimant] as to the symptoms he suffered. Although he said so with less clarity, the same is likely to be true as to [the claimant’s] account of the incident. In my judgment, it is entirely outside the remit of an expert to decide which witnesses of fact he believes or disbelieves.”

In response to the defendant’s counsel’s submission that a medical expert can and should form a view as to whether he believes a claimant, the trial judge said:

“I do not accept this submission as put. Of course, it is entirely proper for a medical expert to say that the medical records are not consistent with what a person claims were his symptoms. However, in failing to appreciate or deal with the possibility that the account of the symptoms provided by [the claimant] might be true, [the defendant’s expert] has deprived the Court of what evidence he might have been able to give if the Court accepted the truth of that account.”

In concluding on the evidence of the respective experts, the trial judge described that of the claimant’s expert as “conservative, clear and persuasive”. By contrast, regarding the defendant’s expert, he stated:

“I regret that I find the problems with [the defendant’s expert’s] evidence do not give me confidence in his expert opinion which, in any event, does not help me in relation to the incident and symptoms I have found.”

The High Court judge hearing the appeal did not dispute any of those observations made by the trial judge and took them into account in dismissing the appeal.

Conclusion

The decision usefully highlights that the function of an expert witness is to help a court come to conclusions relevant to the case rather than be blinded by their own views regarding the credibility of a witness. An expert should give evidence relevant to their field of expertise objectively. They should not give their evidence effectively from the perspective of the party instructing them or tailor their evidence to be consistent with that instructing party’s position regarding the case. Any expert instructed should be clearly advised that their primary duty is to the court which should be performed impartially.

For more information and expert advice on commercial disputes, contact a member of our Commercial Disputes team.

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[1] Allard v Govia Thameslink Railway Ltd [2024] EWHC 2227 (KB) 522