Also known as: independent intervening act · intervening cause · superseding cause
Written by attorneys · grounded in primary & secondary sources — see below
An act by a third party or other force that would have occurred even if the defendant had not acted but that combines with the defendant's conduct to produce the harmful result.
Gretchen shoved Tina toward an exit in violation of a venue ordinance. Tina stumbled onto an unguarded loading dock with no railing and fell to her death. The dock's dangerous condition existed independently of the shove and would have posed the same risk to anyone in the area. The independent nature of the dock defect prevents the shove from serving as the proximate cause of death.
Indigo Textiles left a chemical spill in a walkway that created a foreseeable slipping hazard. A passerby slipped and instinctively grabbed a coworker to break the fall, injuring the coworker. The coworker's instinctive grab was a normal consequence of the spill situation. The intervention therefore does not relieve Indigo Textiles of liability for the resulting injury.
Select any source to read its text and confirm it supports the definition.
Inertia Dynamics negligently stored flammable materials near a public path. A third party later ignited the materials in an unforeseeable act of arson. The resulting explosion caused harm far different in kind from the ordinary fire risk created by the storage. The extraordinary character of the arson supports treating it as a superseding cause.
Ironclad Industries failed to secure a construction site, increasing the chance that vandals would enter and cause damage. Vandals did enter and set a fire that spread to neighboring property. The negligent failure to secure the site created the foreseeable risk of harm through the vandals' intervention. The intervention therefore does not supersede Ironclad Industries' liability.
Ivy Investments negligently left a heavy crate unbalanced on a loading platform. An employee saw the crate tipping and jumped aside in fear, knocking over a coworker. The employee's jump was a normal response to the fear created by the unbalanced crate. The response does not constitute a superseding cause of the coworker's injury.
Imran Iyer left a ladder leaning against a building without securing it. A pedestrian saw the ladder beginning to fall toward a child and rushed to catch it, suffering a back injury in the effort. The pedestrian's attempt to avert the threatened harm was a normal response to the danger created by the unsecured ladder. The effort therefore does not relieve Imran Iyer of liability for the injury.
Independent intervening acts would have occurred even without the defendant's conduct and can break the chain of causation when they are unforeseeable. Dependent acts, such as negligent medical treatment of an injury the defendant caused, arise because of the defendant's act and ordinarily do not relieve the defendant of liability.
Supporting sources
An independent intervening act supersedes the defendant's liability when its intervention prevents the antecedent negligence from remaining a substantial factor in bringing about the harm, as stated in Restatement (Second) of Torts § 440.
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No. An act done in normal response to fear or emotional disturbance that the defendant's negligence substantially caused is not a superseding cause under Restatement (Second) of Torts § 444.
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Courts consider whether the force produces harm different in kind from that otherwise risked, whether its operation appears extraordinary rather than normal, and the degree of culpability of any third-person wrongful act, as outlined in Restatement (Second) of Torts § 442.
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…that death. “The proximate cause of death is that cause which, in natural and continuous sequence, unbroken by any efficient intervening cause, produces the death, and without which the result would not have occurred. It is the efficient cause—the one that necessarily sets in operation the factors that accomplish the death.”…