Also known as: superseding intervening acts · supersede intervening act · superseding cause · intervening superseding cause
Written by attorneys · grounded in primary & secondary sources — see below
An intervening act or force of a third person that by its operation prevents an actor from being liable for harm to another which the actor's antecedent negligence is a substantial factor in bringing about. The intervention must be extraordinary rather than a normal consequence of the situation created by the negligence.
Lena authorized a pressure increase in a gas pipeline. A construction firm had earlier weakened a distant section through unauthorized digging. The pipe ruptured and injured residents. The digging did not relieve Lena of liability because it did not create a harm different in kind from the risk her conduct created.
Luis waved an unloaded pistol at teenagers inside a store to deter shoplifting. One teen panicked and sprinted into the street where a car struck and killed him. The driver's conduct did not supersede Luis's liability because the flight into traffic was a normal consequence of the brandishing.
Select any source to read its text and confirm it supports the definition.
Luis exceeded passenger capacity on a charter boat in choppy seas. A large wave struck and the boat capsized, drowning a passenger. The wave did not constitute a superseding cause because waves are a normal maritime hazard that the capacity rule was designed to address.
Sydney Santos left a defective heater running in a warehouse. A small fire broke out. Simone Sanders rushed in to extinguish it and suffered burns. Simone's rescue attempt did not supersede Sydney's liability because the effort was a foreseeable response to the created danger.
Selena Singh brandished a firearm at a group of teens in a busy store. One teen fled in fear and collided with Solomon Silver, injuring him. The fleeing teen's conduct did not supersede Selena's liability because the flight was a normal response to the fear she created.
Southland Foods stored servers with a latent defect that caused repeated overheating. Staff attempted to cool the units with fans and ice packs. The servers still caught fire and damaged nearby equipment. The staff's cooling efforts did not supersede the seller's liability because they were normal attempts to avert the threatened harm.
An intervening act qualifies as superseding when it prevents the original actor from being liable for harm that the antecedent negligence was a substantial factor in bringing about. The act must operate after the negligence and produce a result different in kind or extraordinary in character.
Supporting sources
No. An act done by another in normal response to fear or emotional disturbance to which the actor's negligent conduct is a substantial factor in subjecting the other is not a superseding cause.
Supporting sources
Normal efforts by the victim or a third person to avert harm threatened by the actor's negligence are not superseding. Only efforts that are grossly careless or extraordinary would break the chain.
Supporting sources
When the negligent conduct creates or increases the foreseeable risk of harm through the intervention of another force and is a substantial factor in causing the harm, the intervention is not superseding.
Supporting sources
Courts consider whether the force brings about harm different in kind, appears extraordinary rather than normal, or involves a third person's wrongful act. The degree of culpability of the third person also matters.
Supporting sources
…manufacturer’s liability is limited only if the subsequent alteration or modification breaks the chain of causation, akin to an intervening superseding cause in negligence law. Southwire Co. v. Beloit Eastern Corp. , 370 F. Sup. 842, 857 n.21 (E.D. Pa. 1974). In other words, a manufacturer “could still be liable because the original defect,…