Ratio Decidendi
Where there are multiple possible causes of the claimant's injury, the claimant must prove on the balance of probabilities that the defendant's negligence was a cause. It is not sufficient to show that the defendant's negligence was one of several possible causes.
Facts
A premature baby received excess oxygen due to a junior doctor's negligence. The baby developed retrolental fibroplasia (a condition causing blindness). However, the condition had multiple possible causes, and excess oxygen was only one of them.
Judgment Summary
The House of Lords held that the case should be retried. Lord Bridge distinguished McGhee v NCB and held that a claimant must prove causation on the balance of probabilities. Where there are several distinct possible causes, merely showing that the defendant's negligence increased the risk was insufficient — the claimant must show it was more likely than not the actual cause.
Key Quotes
"A plaintiff must prove not only that the defendant's act was a possible cause of the injury, but that it was a probable cause."
— Lord Bridge
Subsequent Treatment
Distinguished from Fairchild v Glenhaven in the mesothelioma context. Remains the general rule on proving causation where there are multiple independent potential causes.