## Facts

- The case involved consideration of the standard for accepting expert medical evidence in medical negligence claims.
- Historically, under the Bolam test, a doctor would not be negligent if their conduct was supported by a responsible body of medical opinion.
- The House of Lords in Bolitho examined whether the court must accept such expert opinion if it is uncontradicted, or may reject it for lack of logical defensibility.
- The judgment addressed scenarios where the reasoning behind expert conclusions or accepted medical practices is scrutinised for logical soundness.

## Issues

1. Whether a court is obliged to accept expert medical opinion in negligence proceedings if it is not contradicted by other expert evidence.
2. Whether a responsible body of professional opinion is sufficient or must be supported by logical reasoning subject to judicial analysis.
3. To what extent courts may scrutinise and potentially reject medical expert opinions as part of determining negligence.
4. The relationship between a logically defensible body of professional opinion and proof of causation in medical negligence claims.

## Decision

- The House of Lords held that courts are not required to accept expert medical opinion solely on the basis that it is supported by a responsible body of medical opinion.
- Courts must assess whether that body of opinion is capable of withstanding logical analysis, and may reject opinion evidence if it is not logically defensible.
- The judgment emphasised scrutiny of expert reasoning, methodology, and core assumptions to determine whether accepted practice is based on sound logic and established medical principles.
- It was determined that assertion of commonality or acceptance in the medical community is insufficient; a cogent rationale must underpin the opinion.
- The judgment clarified that for a negligence claim, the breach must both fail the logical defensibility scrutiny and be shown to have caused the alleged harm via a hypothetical analysis.

## Legal Principles

- The Bolitho principle supplements the Bolam test: expert medical opinion must be logically defensible, not merely commonly held.
- Courts have both the power and duty to evaluate the reasoning and methodology of expert opinion in negligence cases.
- Expert evidence is subject to judicial scrutiny regarding its logical basis, not automatic acceptance.
- Causation in medical negligence requires proof that the harm would have been avoided if the defendant had acted in accordance with logically defensible practice.

## Conclusion

The decision in Bolitho v City and Hackney Health Authority marked an evolution in medical negligence law by empowering courts to reject expert opinions lacking logical justification, strengthening judicial oversight of professional standards and clarifying the necessity of both logically defensible practice and causation in negligence claims.


Bolitho v City and Hackney Health Authority [1997] 4 All ER 771 (HL)