Novus Actus Interveniens CASES

In English tort law, novus actus interveniens (a “new intervening act”) is an event that breaks the chain of causation so that the original wrongdoing is no longer a legal cause of the subsequent damage.

Definition and principles

An intervening act breaks the chain where it is independent of the defendant’s breach and renders the later damage not fairly attributable to the original wrong. Key guides are foreseeability, the voluntariness and reasonableness of the intervening act, and whether the later event was a normal response to the situation created by the defendant. Do not conflate novus actus with remoteness or scope-of-duty; they are distinct filters on liability.

Common categories

• Acts of third parties: a free, deliberate and informed act will often break the chain unless it was a very thing the defendant’s breach made likely.
• Claimant’s own act: an unreasonable or reckless decision may break the chain; an act made under pressure or flowing naturally from injury usually will not.
• Medical treatment: subsequent negligence rarely severs causation unless it is so gross and independent that it eclipses the original wrong; contribution between tortfeasors may apply.
• Natural events: extraordinary, unforeseeable acts of nature may break the chain; ordinary vicissitudes typically do not.

Illustrative examples

• Road collision caused by D is followed by negligent surgery worsening injury: chain usually remains intact.
• Officer gives a reckless instruction that creates a new, separate hazard: may constitute a new act breaking the chain from the original driver’s negligence.
• Claimant, frustrated by delay, undertakes a hazardous self-remedy that is wildly unreasonable: may break the chain; prudent remedial steps usually will not.
• Criminal act by a third party: breaks the chain if it was not a foreseeable response to risks created by D; otherwise liability can continue.

Legal implications

• If the chain is broken, damages are limited to loss up to the intervening act; later loss is not recoverable from the original defendant.
• Where later negligence does not sever causation, defendants remain liable for the full damage, subject to contribution between wrongdoers.
• Contributory negligence may reduce damages even where novus actus is not made out.
• The “egg-shell skull” rule still applies: once causation is established, the defendant takes the claimant as found.

Practical importance

Analyse chronology and mechanism early: identify whether the later event was independent and extraordinary, or a foreseeable, normal response. Gather evidence on decision-making (voluntariness, advice), medical standards, and the foreseeability of criminal or natural events.

See also: Causation; Remoteness; Scope of duty; Multiple tortfeasors; Contribution; Contributory negligence; Psychiatric injury; Omissions.