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What is novus actus interveniens?  Novus actus interveniens is a new intervening act or event that breaks the chain of causation, i.e. it breaks the causal link between an original wrongful act and its consequences.  Deriving from a Latin legal term, in the context of tort law, novus actus interveniens can be used as a defence by the Defendant to argue that they should not be held responsible for subsequent events due to the occurrence of an independent, intervening act.  It is important to determine whether an act qualifies as a novus actus interveniens as this will affect the chain of causation, whether it was foreseeable and directly related to the original act.

When is the chain of causation broken?  The intervening must not be reasonably foreseeable and must significantly contribute to the final consequences or result.  The intervening act can be caused by various parties or factors, including the Claimant themself, third parties or even an act of God.


Examples of a break in the chain of causation in personal injury cases

  • Clinical negligence: If one doctor’s negligence, leads to an injury or development of a condition, and a subsequent medical malpractice by another doctor makes the condition worse, this can break the chain of causation.
  • Claimant’s own act: After being involved in an accident at work, where the employer is at fault, a claimant then through his own actions, suffers a separate injury to the same area of the original injury which results in a longer period of recovery, can also break the chain of causation.


How is liability apportioned between two independent tortfeasors?

Courts will generally assess whether the intervening act was foreseeable or unforeseeable.  If the intervening act was unforeseeable and considered a superseding cause that broke the chain of causation, it may limit or absolve the first tortfeasor of liability. However, if the intervening act was foreseeable or a natural consequence of the first tortfeasor’s action, then liability may still be attributed to them.  In general, when there is a break in the chain of causation, the court will review proximate cause to determinate how liability should be apportioned based on foreseeability and directness of causation.


Evidence required to prove a break in the chain of causation:

  • Expert medical evidence: sometimes by way of direct testimony. This involves medical experts providing an opinion on the effect of the intervening act on the Claimant’s claim.
  • Medical records review: medical records help in detailing the sequence of events, treatment provided and their impact on the Claimant’s condition.
  • Forensic medical evidence: may be required in cases where detailed analysis or reconstruction of medical procedure is necessary to determine causation accurately.


Advising clients

It is essential to properly advise your client of the potential effects on their damages that can result from a break in the chain of causation, especially where apportionment is disputed between two Defendants.  Disputed apportionment of causation, can sometimes result in lengthy, complicated and expensive litigation, disputed medical evidence, uncertainty of result.   Where there are likely to be arguments relation to a break in the chain of causation the client should be advised about evidence gathering in early course, to demonstrate a continuous and unbroken link between the Defendant’s action and their injuries to strengthen their case and maximise their chances of receiving fair compensation.


For further information, or to speak to a member of the injury team, please email lyn Edwards at [email protected]