Also known as: superseding causes · intervening cause
Written by attorneys · grounded in primary & secondary sources — see below
An intervening act or force that by its operation after an actor's negligence prevents the actor from being liable for harm that the negligence was a substantial factor in bringing about.
Summit Gas delayed repairs on a known gas leak beneath a residential block. Chase connected a portable grill illegally to a utility line during a street festival. The connection triggered an explosion intensified by the leak that injured Marion. The illegal hookup prevented Summit Gas from remaining liable because it operated as an independent intervening force after the delay.
Sterling Manufacturing left a chemical vat unsecured near a walkway. Serena Soto saw the leaking container and fled in panic, knocking over a bystander who suffered injuries. Soto's flight was a normal consequence of the hazard created by the unsecured vat. Sterling remained liable because the flight did not qualify as a superseding cause.
Select any source to read its text and confirm it supports the definition.
Southland Foods failed to secure outdoor storage bins near a loading dock. An unprecedented downburst storm struck the site and toppled a bin onto a passing delivery driver. The storm's intensity and timing produced harm different in kind from ordinary wind damage. The storm operated as a superseding cause relieving Southland of liability.
Stonehaven Properties left scaffolding unsecured beside a busy sidewalk. A pedestrian bumped the structure while hurrying to catch a bus, causing a plank to fall and injure a nearby shopper. The pedestrian's contact was a foreseeable risk created by the unsecured scaffolding. Stonehaven remained liable because the contact did not constitute a superseding cause.
Solstice Ventures stored unstable crates near an emergency exit. Skylar Sullivan panicked during a false alarm and shoved the crates aside while fleeing, injuring Seth Shapiro who stood nearby. Sullivan's shove was a normal response to the fear created by the unstable storage. Solstice remained liable because the response did not supersede its negligence.
Sebastian Santos left an open trench without barriers near a public path. Stella Shapiro fell in and called for help. A passerby attempted to pull her out but caused additional injury when the trench wall collapsed further. The rescue attempt was a normal effort to avert the threatened harm. Santos remained liable because the effort did not operate as a superseding cause.
A superseding cause is an intervening act or force that prevents the original actor from remaining liable because it breaks the chain of legal causation. An ordinary intervening force continues to operate within the risk created by the negligence and does not relieve the actor of liability.
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A third person's negligent act is not a superseding cause when the original actor should have realized that a third person might so act or when the act is a normal consequence of the situation created by the negligence. The original actor remains liable if the intervening negligence falls within the foreseeable risks.
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An extraordinary force of nature qualifies as superseding only when it produces harm different in kind from that threatened by the negligence or when its operation is extraordinary in light of the circumstances. The force must break the chain of legal causation rather than merely intensify an existing risk.
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Foreseeability determines whether the intervening force is a normal consequence of the risk created by the negligence. When the actor created or increased the foreseeable risk of harm through the intervention of another force, the intervention does not supersede liability.
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…knocks down with his car a pedestrian and a third person then ran over the prostrate person. That involves the question of intervening cause which we do not have here. Moreover it is out of harmony with the current rule on that subject and was properly questioned in Hill v. Peres , 136 Cal.App. 132 [28 P.2d 946] (hearing in…