Few judgments illustrate the fragility of expert credibility as starkly as this one, and every expert witness and instructing solicitor should read it carefully. The Bond Solon article on Tosh v Gupta [2025] EWHC 2025 highlights a case that carries lessons well beyond its own facts. From the perspective of an ophthalmology expert working in civil, family, and criminal cases, the judgment illustrates several failings that have become increasingly visible across disciplines. These failings do not simply weaken a single report. They undermine the trust that courts and solicitors place in the expert witness profession as a whole. Below are the key reflections on the case.
Advocacy is the fastest route to losing credibility
The central problem in this case was not clinical. It was behavioural. Once an expert admits that their report serves a party rather than the court, their independence is irrevocably compromised. CPR 35 is explicit: the overriding duty is owed to the court. That duty is not shared, divided, or negotiated. It is absolute. The moment an expert aligns their opinion with the desired outcome of the instructing party, the expert ceases to be a witness and becomes an advocate. Courts will always back away from such evidence, regardless of clinical experience. The judge's comment that she "unhesitatingly preferred" the defendant's expert was a direct consequence of this breach.
The failure to address the opposing case is a red flag
One of the most revealing aspects of the judgment was the expert's inability to meaningfully engage with the defendant's case. No expert can claim to be independent if their report omits the opposing arguments entirely. A CPR-compliant report must reflect the evidence on both sides, explain areas of agreement and disagreement, and demonstrate balanced reasoning. Ignoring the opposing case does not merely look careless. It looks partisan. Solicitors and judges see this instantly, and it is one of the most common reasons experts lose credibility during cross-examination.
Changing an opinion is acceptable. Hiding it is not.
One of the most concerning features of the case was the expert's reluctance to acknowledge that he had changed his mind. Experts evolve their opinions for entirely legitimate reasons: new evidence emerges, material is clarified, and errors are identified. Under Practice Direction 35, a change of opinion must be notified to all parties without delay. There is nothing improper about revising an opinion. What is improper is to revise it silently and then deny it. Transparency is a hallmark of a reliable expert. Ambiguity erodes confidence.
Relevant experience matters more than years of practice
The expert in this case had decades of clinical experience, but limited practical exposure to the specific procedure in question. Expertise must match the issues. This is an important reminder for all experts, particularly those who have retired or reduced their clinical practice. Courts are increasingly attentive to subspecialty relevance and contemporary standards. Experience is not a universal currency. It must be directly applicable to the clinical scenario.
Wider reflections for the expert witness community
The judgment reflects a recurring pattern in cases where expert evidence falters. In my view, the following principles are essential to avoid similar criticism. First, independence is not optional: experts who try to "help" their instructing party inevitably harm them. Second, reports must evaluate both sides, because an expert who cannot articulate the opposing argument has failed in their duty to the court. Third, changes in opinion must be explicit, since an evolving view is acceptable but concealment is not. Fourth, expertise must be relevant and current, because courts expect expertise that matches the clinical question in front of them. These principles apply whether the case concerns colorectal surgery, ophthalmology, safeguarding, personal injury, or catastrophic litigation.
Conclusion
Tosh v Gupta is a reminder that the expert witness role is a privilege that demands strict adherence to procedure, transparency, and fairness. The failures in this case were not inevitable. They were preventable. For solicitors, the judgment reinforces a practical truth: the quality of the expert witness can shape the trajectory of a case long before trial. Selecting an expert who is independent, experienced, and procedurally disciplined is essential for ensuring that the court receives reliable assistance. For experts, the message is clear. Stay objective, stay balanced, and stay within the boundaries of CPR 35. Your credibility depends on it.
Frequently asked questions
What went wrong for the expert in Tosh v Gupta?
The expert openly accepted that parts of his report amounted to a piece of advocacy for the claimant. Once an expert admits that their report serves a party rather than the court, their independence is irrevocably compromised, and the judge unhesitatingly preferred the defendant's expert.
Can an expert witness change their opinion during a case?
Yes. Experts may legitimately revise their opinions when new evidence emerges or errors are identified. Under Practice Direction 35, a change of opinion must be notified to all parties without delay. What is improper is to revise an opinion silently and then deny having done so.
Does long clinical experience guarantee credibility as an expert?
No. Experience must be directly applicable to the clinical scenario. Courts are increasingly attentive to subspecialty relevance and contemporary standards, and decades of general practice may not suffice where the case turns on a specific procedure.
Related insights
For related analysis, see our commentary on when conduct becomes evidence in Ellis & Ors v John Benson Ltd and the role of the expert witness in ophthalmology. Solicitors instructing on disputed clinical care may also review our medical negligence expert-witness service.