What Chester decided
Chester v Afshar [2004] is the case that put a price on the missing warning. By a three to two majority, the House of Lords modified the conventional test for causation to vindicate a patient's right to be warned. Ordinarily a claimant must show that, but for the breach, the harm would not have occurred. The majority relaxed that requirement where a patient was not warned of a small but material risk that then materialised, holding that the duty to warn would be hollow if breaching it carried no consequence.
The facts
Miss Chester underwent spinal surgery performed by Mr Afshar and developed cauda equina syndrome, a recognised risk of around one to two per cent that she had not been warned about. The surgery itself was carried out competently. She could not prove she would never have had the operation, only that she would not have consented to it when she did, without more time to reflect. She still succeeded. Autonomy, and the warning that protects it, were treated as legally significant in their own right.
Why it matters now
Chester sits between Sidaway and Montgomery in the shift towards patient autonomy. Montgomery later made the duty to disclose material risks central to consent. Chester is the reminder that the remedy has teeth: a documented warning is not a formality, and the absence of one can decide a case even when the technique was impeccable and the risk was rare.
What it means for your clinic
In aesthetics and ophthalmology, the most dangerous risks are exactly the Chester scenario: low frequency, high severity. Vascular occlusion, blindness from filler, serious infection. These are precisely the risks a claimant will say they were never warned about. A record that shows the specific risk was named, explained and understood, with time to reflect, is the document Chester tells you to hold. A generic sheet that lists everything and evidences nothing is not.
Where this sits in the story
Consent and negligence law did not arrive fully formed. It climbed, case by case. You can watch the whole arc, and see what each judgment added to the burden your records carry, in the interactive timeline. The related cases are linked below.
Watch the standard rise: 1957 to today →
Related: Montgomery · Sidaway · McCulloch · Bolam