A recent High Court case highlights what process must be followed if an expert witness changes their opinion following a joint report. Essentially, it is about timing. The court is less likely to view this as suspicious if the change in opinion is conveyed to the opposing party as soon as possible. In addition, the court must be convinced by the expert’s rationale for changing their view.
Facts of the case
The claimants brought a claim against the defendant under a home insurance policy covering the period between 15 October 2013 to14 October 2014. In the Particulars of Claim, dated 1 June 2020, the claimants sought an indemnity for storm damage and subsidence damage at their property.
Two structural engineering experts were instructed – one by the claimants and one by the defendant.
The joint report
On 14 December 2022, the claimants served a structural engineering expert report. For the almost three years, very little progress was made in the claim. The defendant served a structural engineering expert report, dated 5 September 2025.
Then on 13 November 2025, the experts filed a joint report setting out several significant points of agreement. These included:
- That there was no explanation for the absence of “commensurate cracking in the walls in relation to the sloping lounge floor”.
- That there was no evidence of internal wall cracking caused by tree-root-induced subsidence or drainage issues.
- That the kitchen floor needed further exposure to understand why it might slope.
- That there was no evidence that the rear gable wall had been damaged by the 2014 storm and there was no need to scaffold it.
The claimants’ expert’s change of opinion
At the opening of the hearing, counsel for the claimants indicated that their expert wished to have the joint report “adjusted and amended”. The judge understood this to mean that the expert wished to withdraw from some matters agreed with defendant’s expert.
The defendant’s position was that this should not be permitted because the evidence was closed.
The judge allowed the claimants’ expert an opportunity to explain his change of opinion. This was primarily because the expert had written a letter setting out his revised view, which had been served on the defendant before trial, although it was missing from the trial bundles.
The judge said: “I did not think it would be just for me to decide the case without knowing what [the expert] had said about how and why he wanted to change his position from that set out in the written reports.”
The outcome
Attempt to introduce fresh expert evidence
The claimants’ expert answered questions in relation to his change in position.
However, the information provided was not related to the joint report, but to a recent site visit and photographs taken in August 2025, which he wished to show the court. The photographs had previously been served as exhibits to an application seeking a further site visit by the defendant’s expert.
Further questions were unrelated to the expert’s change in position, which led the judge to conclude that “the claimants were obtaining a new expert report orally, by examination in chief, [which] is not the fair or proper process for putting new expert evidence before the court”.
Revised opinion was not persuasive
The experts agreed in the joint report that there was no evidence that the rear gable was damaged by the 2014 storm. In introducing the August 2025 photograph, which showed a hairline crack in the rear gable, it was clear that the claimants’ expert was seeking to withdraw from this aspect of the agreement.
However, the new evidence failed to answer the essential question: how did a crack first observed in 2025 establish damage caused by a storm in 2014?
This led to the judge’s conclusion that the claimants fell “a very long way short” of proving this part of their case.
In summary
The claimants were successful in proving part of their claim – that the front gable of the property was damaged by the 2014 storm.
However, the claimants did not prove that there was any damage to the rear gable by the 2014 storm. Nor did they prove any damage from subsidence.
The issue with the claimants’ expert was not simply that he had changed his opinion. But that his revised opinion lacked an adequate explanation connecting the new observation (the hairline crack) to the 2014 storm.
How we can help
Bond Solon provides training, which covers all the core skills and knowledge expert witnesses are required to fulfil their role compliantly and to best practice standards. We also offer university assessed and certified training programmes that are widely regarded as the industry gold standard by instructing parties.