From an expert’s perspective, the greatest vulnerabilities usually arise long before the hearing. They are created when the report is prepared without sufficient analysis, when important evidence is overlooked or when conclusions are expressed more confidently than the available information permits.
Losing Sight of the Duty to the Court.
The most serious weakness is any indication that the expert has become an advocate for the instructing party. CPR 35.3 provides that the expert’s duty is to help the court on matters within their expertise, and that this duty overrides any obligation to the person who instructed or paid them. Practice Direction 35 similarly requires expert evidence to be independent, objective and uninfluenced by the pressures of litigation.
Cross-examination may focus on whether the expert has consistently interpreted uncertainty in favour of one party, omitted evidence that weakens the claim or used argumentative language more suited to a solicitor’s submission. An expert does not demonstrate independence by being hostile to the claimant or defendant. Independence is shown by applying the same clinical reasoning regardless of which party provided the instructions and by acknowledging evidence that does not support the preferred conclusion.
Accepting the Claimant’s Account Without Testing It.
Many medico-legal opinions depend partly on the history provided during the examination. That history is relevant evidence, but it should not automatically be treated as established fact. A report becomes vulnerable where it repeatedly states that an accident “caused” symptoms merely because the claimant reported that they began afterwards. The expert should distinguish between what the claimant said, what is documented in the records, what was observed clinically and what remains uncertain.
Counsel may identify differences between the report, medical records, witness statement and oral evidence. The expert may then be asked whether the original opinion would change if an important part of the claimant’s account were rejected. Robust reports anticipate this problem by making assumptions clear. It explains whether the opinion depends on the accuracy of a particular history and what effect a different factual finding would have.
Failing to Engage With the Medical Records.
Simply stating that the records have been reviewed is not enough. The expert must demonstrate that relevant entries have been understood and incorporated into the analysis. Cross-examination may expose previous similar symptoms, delayed reporting, gaps in treatment, evidence of earlier recovery or unrelated events that were not addressed in the report. Practice Direction 35 requires experts to consider all material facts, including those that may detract from their opinions.
An adverse record does not necessarily defeat the opinion. A gap in attendance may have a reasonable explanation, and an earlier medical problem may have been materially different. The vulnerability arises when the report ignores the issue rather than analysing it.
An expert who first confronts a significant medical entry in the witness box is placed in a difficult position. The court may reasonably question whether the original opinion was based on a sufficiently careful review.
Reaching a Causation Conclusion Too Quickly.
Temporal association is not the same as medical causation. Symptoms occurring after an accident may have been caused by it, but the expert must still consider alternative explanations.
A report is vulnerable where it states that an injury is “consistent with” the accident and treats that as a complete causation analysis. Consistency establishes possibility. The court usually requires assistance on whether the accident probably caused or materially contributed to the condition.
The expert should consider the mechanism of injury, symptom onset, pre-accident baseline, subsequent events, clinical findings and the natural history of the diagnosed condition. Where there are competing explanations, those alternatives should be addressed rather than silently disregarded.
The opinion may also need to distinguish between the cause of the original symptoms and the cause of continuing disability. An accident may have caused an initial injury without medically explaining every difficulty reported several years later.
Giving a Diagnosis Without Showing the Reasoning.
A diagnostic label is not a substitute for analysis. This is particularly important in psychological and chronic pain claims, where the diagnosis may depend heavily on reported symptoms and
