Also known as: intervening actor doctrine · intervening actors doctrine · intervening-actor doctrine · intervening cause · superseding cause
Written by attorneys · grounded in primary & secondary sources — see below
A set of principles that determine whether an act of a third person or other force intervening after negligent conduct relieves the original actor of liability for resulting harm. The doctrines examine whether the intervention is a superseding cause by assessing factors such as foreseeability, normality of the response, and whether the original negligence created or increased the risk of the harm that occurred.
Ivan Ivanov, an engineer at Apex Gas, approved higher pressure on a corroded segment. Days later a contractor accidentally nicked the line during excavation, causing an explosion that damaged a nearby home. The court applies the superseding-cause rules to decide whether the contractor's conduct cuts off Ivan's liability.
Ines Ibarra sold herbicide to farmer Lopez without warning of its interaction with a common fertilizer. Lopez applied both products and an unexpected hard frost destroyed the crop. The court determines whether the frost counts as a normal consequence that leaves Ines liable.
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The city left a deep utility trench uncovered with only a small cone. Maria swerved at dusk to avoid a parked car and fell in. The court weighs whether Maria's maneuver was an extraordinary intervening force under the listed considerations.
Ortiz Builders left a partially completed scaffold unsecured over a sidewalk despite an engineer's warning. An unusually strong windstorm caused collapse onto pedestrian Perez. The court assesses whether the wind created a foreseeable risk that the original negligence increased.
Apex Properties ignored repeated reports that a stairwell light was burned out. Lydia descended carrying groceries, misstepped in the dark, and broke her leg. The court decides whether Lydia's conduct was a normal response to the hazard Apex created.
Imran Iyer left a deep trench poorly marked on a residential street. Isla Ireland, biking at dusk, swerved to avoid a parked car and fell in. The court evaluates whether her evasive action was a normal effort to avert the threatened harm.
The court decides which legal causation rules apply, including whether an intervening force is superseding. The jury resolves disputed historical facts such as what occurred and whether the original conduct was a factual cause.
Supporting sources
No. An act done in normal response to fear or emotional disturbance caused by the negligence, or normal efforts to avert threatened harm, is not a superseding cause.
Supporting sources
An intervening force is not superseding when the original negligence creates or increases a foreseeable risk of harm through that force and remains a substantial factor in causing the harm.
Supporting sources
Courts consider whether the intervention produces harm different in kind, appears extraordinary rather than normal, or involves a third person's wrongful act, among other listed considerations.
Supporting sources
…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.”…