## Facts

- Ms. Chester suffered from severe lower back pain and consulted Mr. Afshar, a neurosurgeon.
- Mr. Afshar recommended surgical removal of three spinal discs, a procedure carrying a 1-2% risk of nerve damage resulting in paralysis.
- Mr. Afshar did not inform Ms. Chester of this risk prior to obtaining her consent to the surgery.
- The surgery was performed competently, but Ms. Chester suffered paralysis in line with the procedure's known risks.
- Ms. Chester argued she would not have consented to surgery, or would have delayed it, had she been properly informed of the risk.
- The central legal question was whether a doctor’s failure to warn of risks constituted actionable negligence when causation by the breach was not established in the conventional sense.

## Issues

1. Whether a doctor's failure to disclose material risks associated with a procedure makes them liable in negligence, even if the procedure is performed competently.
2. Whether liability can arise despite the possibility that the patient would have consented to the surgery had the warning been given.
3. Whether traditional causation principles should be modified to address breaches of the duty to inform.

## Decision

- The House of Lords (by majority) found Mr. Afshar liable for failing to disclose the surgical risk to Ms. Chester.
- The majority held that the conventional 'but for' causation test should be adjusted to safeguard patient autonomy and give substantive effect to the duty of disclosure.
- The minority would have applied the standard causation test, finding that since Ms. Chester likely would have consented at a later date, liability should not attach.
- The decision established that a breach of the duty to inform patients of material risks can be sufficient for liability, even absent traditional causation.

## Legal Principles

- The duty of medical professionals extends beyond competent performance to full disclosure of material risks to patients.
- Patient autonomy is central; informed consent is required for lawful medical intervention.
- The 'but for' test of causation may be adjusted in certain circumstances to uphold the substance of a doctor's duty to inform.
- Liability for non-disclosure does not necessarily require proof that the patient would never have undergone the procedure, only that the breach deprived them of the opportunity for informed choice.
- There remains judicial debate on whether and when traditional causation rules can be modified in medical negligence.

## Conclusion

Chester v Afshar established that doctors may be liable for failing to warn patients of material risks, even if their actions do not meet the conventional causation threshold, in order to protect the principle of patient autonomy and strengthen the obligation of informed consent in medical practice.

Chester v Afshar [2004] 3 WLR 927 (HL)