Chester v Afshar

[2004] UKHL 41; [2004] 4 All ER 587
House of Lords
October 2004

Modification of conventional causation principles to provide remedies where duty had been breached. The strict requirement in tort that the Claimant prove that the Defendant's negligence had caused the harm suffered was modified to permit a claim where a patient could not show that, had her surgeon complied with his duty to warn her of the risks of the surgery, she would never have consented to the operation.

Miss Chester had suffered repeated episodes of back pain. Between 1988 and 1994 this was treated conservatively through a course of injections. In 1994 Miss Chester was referred to Mr Afshar, a consultant neurosurgeon, who advised and performed surgery. As a result of the surgery Miss Chester suffered the rare, but recognised, complication "cauda equina syndrome", causing partial paralysis. The operation was not performed negligently and there was nothing to suggest that the chances of the complication occurring, estimated at between 1-2%, were increased by the manner in which Mr Afshar performed the surgery.

The issue before the House of Lords was whether Mr Afshar was liable to Miss Chester for failing to warn her, prior to performing the operation, of the danger of the complication occurring. One of the tortious duties imposed on surgeons is to warn patients of the risks of any proposed surgery, so as to enable them to make an informed decision about whether to undergo that surgery - the doctrine of "informed consent". It is accepted that, if a claimant can show that, had she been informed of the risks, she would not have consented to the surgery, the surgeon will be liable for any damage resulting from the realisation of those risks. The difficulty in the present case was that Miss Chester was unable to show that knowledge of the risk would have altered her decision to consent to the operation - all that she could show was that it would have caused her to delay her decision, pending possible further opinions. As such, the conventional "but for" test applied in tortious cases was not satisfied: it could not be said that, but for Mr Afshar's failure to warn his patient of the risk, Miss Chester would not have consented to the operation and thus not have suffered the resulting damage. Nor could it be said that the risk was increased by the failure to warn: it existed as an inevitable risk of the operation, regardless of how skilfully the operation was performed.

The Lords held by a majority of three to two that, in order to do justice, conventional causation principles must be modified in the present case to allow the claim. Causation issues could not be separated from policy considerations: the function of the law was to enable rights to be vindicated and to provide remedies where duties had been breached. The injury suffered was within the scope of Mr Afshar's duty to warn. Mr Afshar had accordingly violated his patient's right to make an informed choice: Miss Chester could not be said to have given informed consent to the surgery "in the full legal sense".

The decision of the Lords to modify the tried and trusted causation test is a momentous one. The only parallel is the case of Fairchild v Glenhaven Funeral Services Ltd [2003] 1 AC 32, an asbestos case in which the test was modified to overcome the fact that the claimant employees could not prove which of their employers (all in breach of their duty to minimise the risks of exposure to asbestos dust) had been responsible for the actual exposure which resulted in the onset of mesothelioma. In Chester v Afshar the Lords recognised that such modifications were exceptional, but also that they could not be limited to a particular set of facts. However, Chester arguably represents a significant extension of the situations where the strict requirement to show causation will be overlooked: in Fairchild it was impossible to show which employer was actually responsible for the critical exposure - therefore causation could not be technically proved. On the facts of Chester, it would be possible for a claimant to prove that, had she been warned of the dangers, she would definitely not have consented to the operation; the reason it could not be proven in Chester was because there was no conclusive evidence that the Claimant would have come to this decision.