When Changing Your Expert Opinion Becomes a Risk: Reflections on Andrews v Kronospan Limited [2025]
One of the most difficult positions an expert witness can find themselves in is this: you have completed your analysis, agreed a common approach with the opposing experts, and the results are not what your instructing party hoped for. At that point, professional instinct, intellectual curiosity, and legal duty can start pulling in different directions.
A recent High Court decision, Patricia Andrews & Ors v Kronospan Limited [2025] EWHC 2429 (TCC), offers a reminder of how carefully courts examine expert evidence when an initial approach is later revisited. While the case itself concerns environmental nuisance and not aesthetic medicine, the principles it reinforces are directly relevant to anyone acting as an expert witness in any industry.
At its heart, this case is not about whether experts are allowed to change their minds. It is about when such a change is justified, and how quickly credibility can be undermined if the motivation behind it appears anything other than purely objective.
Consistency, not rigidity
I don’t believe that experts are expected to be inflexible. Medicine, science, and data analysis are rarely static, and courts understand that evidence can evolve. What they do expect, however, is consistency of method and transparency of reasoning.
In Andrews v Kronospan, all four experts initially agreed on a common methodology for modelling dust data. When experts align on an approach, it signals to the court that the methodology is sound and balanced. Departing from that agreed position later places the burden firmly on the expert seeking change to justify why.
In this case, the claimant experts revised their approach after being dissatisfied with the initial results. While dissatisfaction alone is understandable, the court examined if that dissatisfaction was rooted in objective scientific necessity or influenced by the outcome those results produced.
That distinction is critical in expert work.
Outcome-driven revisions and perception in court
One of the most interesting aspects of the judgment is not that the claimant experts were accused of misconduct (they were not), but that the judge was concerned with how their actions could reasonably be perceived.
The revised analyses produced results more favourable to the claimants’ case. The court was clear that where a revised opinion aligns more closely with the instructing party’s interests, it will be scrutinised “particularly critically”.
This is an important lesson for all experts. Courts are acutely aware that experts are instructed and paid by parties with a vested interest in the outcome. Even when an expert genuinely believes they are refining or improving their work, the timing and effect of that refinement can raise questions about independence.
As an expert witness, your role is not to make the case stronger. It is to assist the court.
The danger of “fixing” inconvenient evidence
In my medico-legal work, I sometimes see a similar tension arise. An expert may feel uneasy when their opinion does not support the claim or defence as anticipated. There can be a temptation to revisit the evidence in the hope that a different angle, a different interpretation, or more analysis might align things more comfortably.
This case reinforces that revisiting evidence because it feels incomplete or flawed is not the same as revisiting it because the conclusion is inconvenient.
The court in Andrews v Kronospan emphasised that a change of approach must be justified on a purely objective basis, and that the revised analysis must be demonstrably preferable to the original. Simply believing the new results “make more sense” is not enough if the methodology itself departs materially from what was previously agreed.
In expert practice, intention is less important than justification. Courts do not assess what an expert hoped to achieve, but if the change was necessary, proportionate, and methodologically sound.
Departing from agreed approaches between experts without compelling reason places the expert in a vulnerable position. As this case shows, even a well-argued revised analysis may carry less weight than a consistent, well-reasoned opinion that adheres to the original methodology.
For experts, this shows the importance of investing time and care right at the beginning. Agreeing a methodology should never be treated as a provisional step that can be revisited if the results are unhelpful.
Independence is demonstrated, not declared
Experts often emphasise their independence in reports and oral evidence. While such statements are expected, independence is ultimately judged by conduct.
Courts look at patterns: when changes are made, why they are made, and who benefits from them. A revised opinion that coincidentally strengthens the instructing party’s case will inevitably be examined through that lens, regardless of the expert’s integrity.
This does not mean experts should fear acknowledging limitations or errors in their work. On the contrary, openly correcting a genuine mistake can strengthen credibility. What this case cautions against is analysis driven by a desire to achieve a different outcome.
Lessons for expert witnesses
The takeaway from Patricia Andrews & Ors v Kronospan Limited is not that experts must never change their minds. It is that expert evidence is persuasive not because it is helpful to one side, but because it is robust under scrutiny.
Experts best serve the court when they are willing to stand by conclusions that may be unwelcome, when they resist the urge to refine analysis purely to “see if it helps”, and when they treat agreed methodologies as commitments.
In medico-legal aesthetics, a field already under increasing scrutiny, these principles matter a lot. An expert’s credibility is built slowly and can be weakened quickly. Once the court senses subjectivity creeping into analysis, even unintentionally, the evidential weight of that opinion may be diminished.
This case is a clear reminder that how we arrive at our opinions matters just as much as the opinions themselves.