When Expert Evidence Fails: My Commentary on the Tosh v Gupta Judgment

ijeeva
Nov 23
3 min read

The Bond Solon article on Tosh v Gupta [2025] EWHC 2025 highlights a case that every expert witness should read carefully. It is uncommon to see an expert openly accept that parts of their report amounted to “a piece of advocacy for the claimant”, and even more uncommon to see the ripple effect that admission has on the credibility of the entire report.

From my perspective as 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 my key reflections on the case.

1. 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.

2. 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
demonstrate balanced reasoning

Ignoring the opposing case does not merely look careless. It looks partisan. Solicitors and judges see this instantly.

In my experience, this is one of the most common reasons experts lose credibility during cross examination.

3. 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.

Errors are identified.

Under PD 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.

4. 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.

5. 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:

A. Independence is not optional

Experts who try to “help” their instructing party inevitably harm them.

B. Reports must evaluate both sides

An expert who cannot articulate the opposing argument has failed in their duty to the court.

C. Changes in opinion must be explicit

An evolving view is acceptable. Concealment is not.

D. Expertise must be relevant and current

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.

Stay within the boundaries of CPR 35.

Your credibility depends on it.