Causation — factual and legal
Factual causation, legal causation, and the limits of liability in tort.
Overview
Causation is the conceptual bridge between breach of duty and recoverable damage. A claimant who has established that the defendant owed a duty of care and breached it must still prove that the breach caused the relevant harm. This requirement performs a double function: it ensures the defendant is held liable only for losses genuinely attributable to wrongdoing, and it cabins the law's reach in a world where consequences ripple indefinitely.
English law conventionally divides causation into two stages. Factual causation asks whether the defendant's breach was a conditio sine qua non of the damage—a necessary link in the chain of events. This enquiry is dominated by the but-for test: would the claimant have suffered the same loss if the defendant had not been in breach? Legal causation (sometimes labelled remoteness or scope of duty) asks whether, as a matter of law and policy, the defendant ought to bear responsibility for that damage. Even when factual causation is established, the law may refuse recovery if the damage is too remote, if an intervening act (a novus actus interveniens) breaks the chain, or if the loss falls outside the scope of the duty breached.
The distinction between the two stages is analytically convenient but often unstable in practice. Courts have recognised that purely factual enquiries can be manipulated by choice of counterfactual, and that legal causation frequently smuggles in considerations—such as fairness, policy, and moral intuition—that are denied at the breach stage. Recent scholarship, particularly by Stapleton and Steel, has challenged the utility of the but-for test as a universal gateway and has argued for a more explicit engagement with the normative reasons that underpin causal attribution. The Supreme Court's decisions in Sienkiewicz and Hughes illustrate the doctrinal sophistication—and the remaining tensions—in this area.
This note proceeds chronologically and thematically. After sketching the historical emergence of causal requirements in nineteenth-century trespass and case, we set out the core principles governing each stage. Statutory interventions (most notably the Compensation Act 2006) are examined, before turning to the landmark authorities that have shaped modern doctrine. Doctrinal development traces the erosion of rigid rules in favour of multi-factorial enquiries, and the academic debates section canvasses competing theoretical accounts of causal responsibility in tort.
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