Novus Actus Interveniens: Meaning, Elements and Exceptions

By | November 20, 2020
Novus Actus Interveniens

The Latin terminology of novus actus interveniens or nova causa interveniens is characterised as the action of an independent third party. The Black Law Dictionary defines it as an intervening cause. This article provides an insightful analysis of novus actus interveniens and its various aspects.

I. Introduction

Novus actus interveniens is characterized as an occurrence that happens in a series between the initial event and the outcome, thus altering the normal course of events that might have linked a wrongful act to an accident. In the teachings of causality, novus actus interveniens later evolved into one of the doctrines that were popularised by H.L.A. Hart and A.M. Honore in their book entitled Causation in Law [1], which was first published in 1959.

Hart and Honore were also Oxford University professors of Jurisprudence. Another British scholar, Williams, said that a prudent actor, who has a clear understanding of what he is doing and is not subject to coercion, harassment or error, will usually work to relieve the perpetrator of responsibility for a further effect of the current interfering act or novus actus interveniens. It renders the effect way too remote.

The complainant must prove that the loss they sustained was caused by the defendant in order to show causation in tort law. A straightforward implementation of the ‘but for[2]‘ test in most situations would address the problem of cause in tort law i.e., ‘but for the conduct of the defendant, will the complainant have sustained the loss?

If so, the criminal is not responsible. If not, the defendant is accountable. Where more than one potential cause occurs, correlation can be troublesome. To alleviate the burden of proving cause in such cases, different formulations have emerged.

Causation typically consists of two components that decide whether a person should be held responsible for the harm incurred to another party or not — Factual cause and legitimate causation. In the case of Groenewald v. Groenewal, a complete and lengthy description of all aspects can be sought[3]. Another frequently missed aspect of causation, though, is that of novus actus interveniens. The crime may be the act of the perpetrator, a third party’s act, or an act of god. Not each interfering act, however, counts as Novus actus interveniens.

The intervening act must be such that it is not inevitable or planned, however in some situations, where the intervening act is a ‘free deliberate and informed act’ by another agent, notwithstanding the effect being an intended consequence, the original causation breaks[4].

II. Understanding novus actus interveniens

Novus actus interveniens is Latin for a “new intervening act”. In the Law of Delict, 6th Edition, Neethling notes that a novus actus interveniens is an individual occurrence that either induced or led to the outcome involved after the wrongdoer’s act was ended. A novus actus splits the causal chain between the conduct of the original wrongdoer and the responsibility imputed to him or her as a consequence of it.

A criterion for an act or omission performed to be a novus act after the original act of the wrongdoer is that the secondary act was not fairly foreseeable. Whereat the time of the initial misconduct, the resulting occurrence was fairly probable, it is not to be called a novus actus capable of restricting the responsibility to be apportioned to the original wrongdoer.

A novus actus is not limited strictly to factual or legal causation and at any stage will disrupt the causal chain. A novus actus interrupts the link between the unjust act of the original wrongdoer and the effects of his act, with regard to a factual cause, to the degree that it frees him from the burden of his acts.

However, the considerations of procedure, equity, reasonableness and justice must be taken into consideration when determining novus actus with respect to moral responsibility in order to decide whether blame for the initial wrongdoing should now be imputed to the original wrongdoer and whether the causal chain has been broken. A novus actus thus disrupts the “directness” element of the original act and it is difficult to satisfy the arbitrary test of legal causation[5].

To put it plainly, novus actus interveniens serves to break the chain of causation between the unjust act or inaction of a defendant and the damage incurred by the claimant.

III. Elements of novus actus interveniens

In order to decide whether or not an event or act will bear the legal weight of novus actus interveniens, any of these would usually be:

  • Human behaviour that should be fairly treated as voluntary; or
  • A causally distinct phenomenon, the relation of which is too exceedingly unlikely to be considered a coincidence by ordinary circumstances of the incorrect act or omission.

The authority for this test is Haber v Walker (1963).

If a complainant who has sustained a minor leg fracture due to the negligence of the defendant tries to leap from a roof, breaking their leg, it is an example of a voluntary human action[6] that may sever the chain of causation for negligence. Here, the voluntary human intervention of the complainant will break the connection between the actions of the defendant and the damage sustained now.

A third party’s voluntary human intervention may also break the chain of causation. For example, if the complainant with the minor leg injury was fired by a third party in the leg, it would also sever the connection between the actions of the defendant and the damage now sustained.

An example of a causally independent event that may sever the chain of causation for negligence might be when an asteroid is hit from space in the same leg by a plaintiff that has sustained a minor leg fracture due to the negligence of the defendant. Here, the causally autonomous occurrence will break the link between the actions of the defendant and the damage now sustained[7].

Since a novus actus is an “independent” act of intervention, someone or something other than the original wrongdoer can cause it. This general type often involves his or herself, another third party or even an act of God and the wounded party. Therefore, an injured patient who steps on a slippery floor after being injured after additional treatment will have created his own novus actus, or a novus actus will also be considered if a storm does further and greater damage to a property after it has been destroyed by a wrongdoer.

Initial wrongdoers who wish to show that their fault is limited or non-existent and can be imputed to another party also use novus actus as a shield. It must be differentiated from incompetence in donations. If an act or inaction happens before the event that causes the accident, that is known as contributory negligence, such as when a passenger fails to wear a seatbelt in a motor car, he or she is reckless in contributing. Whereas a novus actus is an individual act that happens after the event that causes damage, such as when a passenger is hospitalised following a collision with a motor car and sustains additional hospital injury.

In Weld Bundell b. Stephens[8], The respondent, a chartered accountant, was hired by the appellant to examine the affairs of a corporation. He issued written orders containing matters that were disgraceful to two company leaders. These directions were passed by the respondent to his partner, who irresponsibly left them on the floor of the company’s office.

The manager of the company discovered them and communicated their contents to authorities who then recovered penalties from the appellant for the libel. The appellant was only entitled to recover negligible damages in the present action. On the basis of liability for his real damage in the libel action, he was unable to compensate because the action of the manager was the voluntary act of a private agent for which the appellant had no power and over whose actions, he was not liable[9].

IV. Examples of novus actus interveniens

A, for instance, drops a cigarette butt at the side of the forest in the trees. B immediately pours fuel into the trees, which sparks a forest fire, unbeknownst to A. Is it the deed of A that sparked the forest fire because he didn’t want to burn the forest down? The forest fire is not the fault of A; it is the action of B that triggered the forest fire. B is not an instrument of A in this situation, and A has not instructed or recommended B to spill fuel on the cigarette butt to burn the tree, it is merely an act of B’s own initiative.

Without being an ingredient of the partnership with A, he was exploiting the situation and triggering a storm. If A and B both wanted to burn the tree, it is a separate situation that they had the same intention of burning the forest, and that common intention would result in a forest fire. Meanwhile, A had no intention of burning the forest in the case mentioned in this paragraph, while B purposefully poured gasoline over the cigarette butt that ignited the fire.

Thus, only B and not A may be assigned to an aspect of malicious intent (mens rea). Therefore, in deciding if there is interference by another actor that eliminates or erases the obligation of the first actor, moral considerations become essential.

For contrast, here’s yet another example; A hits B, and B loses his equilibrium as a result. As stumbling, B slams into a glass window until it shatters. We can say in this situation that A caused B to lose his balance and crack the glass of the window, but we can’t say that A shattered the glass of the window. In brief, it may be assumed that the action of A provides credence or commitment to the shattering of the glass of the window.

In the latter example, B has no intention of smashing the window, but because of A’s deed, he forced the window glass to shatter. Likewise, A had no intention of shattering the glass in the frame. A is also liable, though, and he should have been able to foresee the consequences of his action. And it is not possible to blame 100 per cent of A for the extent of responsibility for shattering the window glass. Meanwhile, in addition to him having no intention of shattering it, B’s act of breaking the window glass is carried out. The rupture of the window glass is an event that occurred accidentally and is not a voluntary act.

V. Exceptions to novus actus interveniens and Case Laws

  1. Where the defendant has knowingly procured the intervening act.
  2. Where there is no full responsibility for the interfering actor.
  3. Where the act that intervenes is one as may fairly be expected.
  4. Where a simple reflex or spontaneous action is the intervening act.

In the case of The City of Lincoln, there was a collision attributable to the steamers’ own liability between a steamer (whose owner is the defendant) and a barge (whose owner is the plaintiff). After the crash, the steering compass, maps and other methods used for guiding the ship were lost.

The Captain on the barge wanted to search for a port to safeguard the ship from sinking and the barge without any error on the part of the Captain and his crew members and because of the unavailability of the required navigational equipment, the ship suffered an accident due to the effect of the ship on the seabed or waterway side (ship grounding) that destroyed the ship. The complainant sued the defendant.

The Court of Appeal ruled that the decision of the Captain to hunt for a safety port was a fair move that did not break the causal chain and was attributable to the accident that prompted the Captain to take the decision and resulted in the ship’s grounding. The Captain had two options to deal with the crisis, either by remaining there or waiting for any external assistance or looking for a security port, all of which required high risk but were rational actions. It was also concluded that the Captain’s decision to follow one of the routes would not sever the causal chain.[10]

A category of interfering acts still exists, not those taken by the complainant himself or any third party, but acts attributed to nature itself sometimes referred to as “acts of God”. Such an act can be seen in the Royal Norwegian Government v. Carslogie Steamship Co Ltd[11].

The argument was dismissed by the judges, and so the claimant was found liable only for damages resulting from the first collision, not the subsequent damage to the storm. The storm was deemed to be a novus actus interveniens, and so the claim was based on a mistaken reading of causation. In fact, the courts acknowledged that the damage to the hurricane was incidental i.e., it may have occurred on any ship on any voyage, and thus could not be regarded as a result of the initial crash.

An example is Knightly v. Johns[12], where the incompetence of a police officer when directing traffic after a road collision negated the motorist’s responsibility whose carelessness culminated in the initial accident. However, it is relatively uncommon for the defence to prevail if the claimant’s own conduct is claimed to have breached the chain of causation. An unusual example is McKew v. Holland & Hannen & Cubitts (Scotland) Ltd[13].

A complainant who fell down a flight of stairs argued that the injuries he sustained were attributed to his bosses, as one of his legs had unexpectedly gone numb due to an earlier workplace accident for which they were responsible, resulting in the crash. However, the House of Lords ruled that while probably unavoidable, the claimant’s own act of descending the stairs without waiting for the support that was available broke the causal connection between his fall and the initial industrial accident.

VI. Conclusion

The continuity of events can be disrupted by a new unpredictable occurrence that cannot possibly be a predictable complication. For such cases, novus actus interveniens takes place as the judicial processes in the case are changed. If death is due to recent and unrelated actions, the attacker is not held liable for the death of the victim.

With regards to tortious claims, Novus actus is a diverse instrument that can often be used as part of one’s evaluation of a lawsuit.

It is necessary to ensure that when evaluating cases relating to tortious damages, there have been no subsequent actions that may have severed the causal chain with respect to liability. This is also a factor that is ignored or only established through lawsuits at a far later point. Therefore, in order to ensure that all the facts are before you when reviewing a matter, it is important that thorough inquiries are conducted. A novus actus interveniens has the purpose of restricting the liability of a defendant and can also be a valuable instrument when determining claimants for damages.


[1] Hart, H.L.A., & Honore, A. M. (1959). Causation in the Law, 1st Edition. Oxford: Oxford University Press

[2] Barnett v. Chelsea & Kensington Hospital [1969] 1 QB 428, Available Here

[3] Groenewald v. Groenewald 1998 (2) SA 1106 SCA.

[4] Jeremty Horder & Andrew Ashworth, Principles of Criminal Law 104 (7th ed. 2013)

[5] Boberg, P. Q. R. (1959). Reflections on the Novus Actus Interveniens. The South African Journal, 76 S African L. J. 280.

[6] Carslogie Steamship Co Ltd v Royal Norwegian Government [1952] AC 292 (HL).

[7] ‘Novus Actus Interveniens’ Raphael Powell, M.A., B.C.L., Current Legal Problems, Volume 4, Issue 1.

[8] Weld-Blundell v. Stephens, [1920] UKHL 646.

[9] Hogan Lovells Publications | February 2017, “Novus actus interveniens.”

[10] The City of Lincon, (1816) 1 Stark 492.

[11] Carslogie Steamship Co Ltd v. Royal Norwegian Government [1952] AC 292 (HL)

[12] Knightly v. Johns [1982] 1 WLR 349, [1982] 1 All ER 851

[13] McKew v. Holland & Hannen & Cubitts (Scotland) Ltd [1969] 3 All ER 1621 (HL), 8 KIR 921.

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Author: Vatsala Sood

Student at Symbiosis Law School, Pune

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