Chester v Afshar  3 WLR 927
Establishing causation following consent to medical treatment and subsequent injury.
The claimant Chester, had managed with bad back pain for several years, which severely limited her ability to walk around and interfered with her ability to control her bladder. A medical examination and test revealed a problem with her spinal cord, and subsequently her doctor, the defendant, advised that she undergo surgery to remedy the problem. Notably, this surgery carried a very minor risk (1% approximately) that it would in fact worsen the issue, however the claimant had not been warned of this risk by the defendant. The claimant agreed to the operation, which was carried out responsibly, however she fell within the 1%. The claimant subsequently submitted she may not have consented to the surgery had she been aware of the possible risks. At first instance, the judge determined that whilst the defendant had not been negligent in his surgical performance, he was liable for having failed to adequately inform the claimant of the risks, as had the operation been performed on an alternative date, her injuries may not have been exacerbated. At first appeal, the Court of Appeal approved the initial judgment.
The defendant appealed, submitted that there was no causation as the likelihood of the claimant having consented to the operation at some point did not alter the fact that the operation bore risks.
The House of Lords dismissed the appeal (in a 3 – 2 split decision), holding that the defendant had failed in his tortious professional duty, satisfying the ‘but for’ test, and that the claimant deserved a remedy.