Chester v Afshar [2004] UKHL 41, [2005] 1 AC 134 (HL)

Facts

The claimant suffered from chronic back pain and consulted the defendant neurosurgeon, who advised surgery. The surgeon failed to warn her of a small (1–2%) inherent risk of serious nerve damage associated with the procedure. The risk was not due to negligence in performing the operation, but was an unavoidable complication.

The claimant underwent the surgery and unfortunately suffered the very complication about which she had not been warned. She could not prove that she would never have had the surgery if properly warned. Instead, she argued that she would have delayed it to seek further opinions.

It was accepted that even if the surgery had been performed on a different day, the same risk would have existed.

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Issue

Can causation be established where a doctor negligently fails to warn of a small inherent risk, and that very risk materialises, even though the patient cannot prove she would have avoided the surgery altogether?

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Decision

By a narrow majority, the House of Lords held in favour of the claimant. The failure to warn was treated as causative of the injury, even though traditional “but for” causation was not strictly satisfied.

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Legal Principle

In exceptional circumstances involving failure to warn of inherent medical risks, causation may be established where the very risk that should have been disclosed materialises. The decision reflects a modification of orthodox causation principles in order to vindicate patient autonomy.

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Importance

• Recognises the central importance of informed consent in medical law.

  
  

• Represents a limited departure from strict “but for” causation.

  
  

• Often viewed as policy-driven, aimed at protecting patient autonomy.

  
  

• Its scope is confined and has not been treated as a broad exception to causation principles.