The Court of Appeal has dismissed an appeal against a finding of clinical negligence based, in part, on the trial judge's approach to evaluating expert evidence where a close connection between the defendant and his expert witness had not been disclosed: EXP v Dr Charles Simon Barker [2017] EWCA Civ 63.

The Court of Appeal held that the trial judge had been fully entitled to take the view that the expert had so compromised his approach that the weight to be accorded to his views must be considerably diminished. It went so far as to say that, had the trial judge taken the decision to exclude the expert's evidence entirely, the Court of Appeal would have supported that decision.  

The decision reaffirms the importance of parties and their expert witnesses frankly disclosing any connection which might affect an expert's independence.

Rachel Lidgate, a senior associate in our disputes team in London, considers the decision further below.


The background to the decision is set out in our blog post on the High Court's decision. In brief summary, the claimant brought a clinical negligence claim against the defendant alleging that he had negligently failed to spot an aneurysm on an MRI of her brain. The CVs of the defendant and his expert showed that they had worked in the same hospital department over the same period, but did not indicate any connection beyond that. In fact, as emerged in cross-examination at trial, the defendant had been trained by the expert, they had worked closely together over a substantial period, and they had also collaborated on academic publications.

The High Court (Kenneth Parker J) concluded that the expert's evidence could be admitted (although this decision was described as finely balanced).  However, the judge considered that he must "bear powerfully in mind" the reservations he retained about the expert's independence in assessing the weight he should give to his evidence. He said he had not found it easy to resolve the conflict between the two experts, but ultimately concluded that he should accept the claimant's expert evidence on the basis that his confidence in the defendant's expert's independence and impartiality had been substantially undermined.

The defendant advanced five grounds of appeal, including three relating to the judge's approach to the expert evidence:

  1. Having admitted the expert's evidence, the judge failed to evaluate it on its merits;
  2. The judge wrongly performed a "balancing act" between the rival expert opinions; and
  3. The judge erred in holding that the expert had an interest in the outcome of the case that was sufficient of itself to dismiss his expert opinion when set against that of the claimant's expert witness.


The Court of Appeal dismissed the appeal, Irwin LJ giving the lead judgment with which Henderson and Black LJJ agreed.

Irwin LJ referred to the judge's conclusion that in light of the expert's approach, the decision to admit his evidence was finely balanced, and the weight to be accorded to that evidence must be considerably diminished. In Irwin LJ's view, the judge was fully entitled to take that view. Indeed, he said, had the judge decided to exclude the expert's evidence entirely, that would have been a proper decision. He added:

"Our adversarial system depends heavily on the independence of expert witnesses, on the primacy of their duty to the Court over any other loyalty or obligation, and on the rigour with which experts make known any associations or loyalties which might give rise to a conflict."

The defendant's expert had failed to do so here, despite an express direction to include in the expert reports any employment or activity which raised a possible conflict of interest. Indeed, the fact that the defendant's and the expert's CVs had omitted any mention of papers they had co-authored suggested they might have sought to avoid the connection coming out.

Further, there was good reason to doubt the defendant's expert's approach, including that he had failed to point out that another of the defendant's experts was relying on an academic study he knew to have been discredited.

For all of these reasons, the judge had been fully entitled to reject the expert's evidence.

Rachel Lidgate
Rachel Lidgate
Senior associate
+44 20 7466 2418