Also known as: substantial causes · substantially cause · substantially causes · substantial causation · substantial factor · substantial-factor test
Written by attorneys · grounded in primary & secondary sources — see below
A criterion for determining legal causation in negligence cases under which a defendant's conduct qualifies as a cause of harm if it played a meaningful role in bringing the harm about. The test permits liability when the defendant's negligence supplied one of two independently sufficient forces that together produced the injury. It also guides the allocation of decision-making authority between court and jury on questions of factual contribution and apportionment.
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Simone Sanders stored space heaters near faulty wiring in a storeroom. An unrelated power surge from a neighboring tenant ignited a fire. Either the wiring defect or the surge alone would have started the blaze that destroyed Steven Silva's stored property. A jury may treat Simone's storage decision as a substantial cause of the loss even though the surge was non-negligent.
Stella Shapiro left a heavy sculpture unsecured on an unstable pedestal despite repeated warnings. During a crowded event a child bumped the pedestal and the sculpture fell on Samantha Stone. The museum's failure to secure the pedestal operated continuously until the moment of impact. The unsecured condition remains a substantial cause of Samantha's injuries.
Sydney Santos failed to repair a broken exterior lock at a hotel. Three days later a rideshare driver propped the door open with a rock and an intruder entered and assaulted Sebastian Santos. The hotel's prolonged inaction created the condition that the later acts exploited. The broken lock is still a substantial cause of the guest's injuries despite the unusual sequence.
Sierra Solutions placed donated heaters near faulty wiring. An innocent power surge from Urban Charity combined with the wiring defect to start a fire. The evidence shows the two forces were each independently sufficient. The court must decide whether a jury could reasonably find Sierra's wiring placement a substantial cause before sending apportionment questions to the jury.
Synergy Systems and Sterling Dynamics each operated trucks with defective brakes on the same steep grade. A rockslide blocked the road and both trucks struck Silas's vehicle. The impacts produced indivisible injuries. The jury must decide whether each company's brake defect was a substantial cause and how to apportion the resulting harm.
Skyline Construction misrepresented the legal status of a building permit to a buyer. The buyer justifiably relied on the statement and purchased the property. The reliance directly shaped the decision to close the deal and incur loss when the permit proved invalid. The misrepresentation qualifies as a substantial cause of the buyer's pecuniary harm.
No. When two forces each sufficient to produce the harm operate together, one arising from negligence, the negligent actor's conduct may still be treated as a substantial cause. The test asks whether the defendant's negligence played a meaningful role, not whether it was the sole cause.
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…to the facts of this case. On the record before us, it is clear that Ake’s mental state at the time of the offense was a substantial factor in his defense, and that the trial court was on notice of that fact when the request for a court-appointed psychiatrist was made. For one, Ake’s sole defense was that of insanity. Second,…
…be shown that racially discriminatory acts of the state or local school districts, or of a single school district have been a substantial cause
…consequence of the robbery. So long as a victim’s predisposing physical condition, regardless of its cause, is not the only
…knowledge or belief as to the result is immaterial if he causes the result purposely' or knowingly' by an act that is a
The jury decides whether the defendant's conduct was a substantial factor in causing the harm and how to apportion the harm among multiple causes. The court decides only whether the evidence creates a triable issue or whether apportionment is possible as a matter of law.
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No. If the actor's conduct is a substantial factor in bringing about the harm, the fact that the actor neither foresaw nor should have foreseen the extent of the harm or the manner in which it occurred does not prevent liability.
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Yes, provided the intervening act is not so extraordinary that it breaks the chain of legal causation. The original negligence remains a substantial cause if it created a condition that made the later act a normal incident of the risk created.
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The plaintiff must show that the defendant's negligence played a meaningful role in producing the harm. Evidence that the harm would have occurred even without the negligence defeats the substantial-cause showing, but the mere presence of other contributing forces does not.
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