The difference between an intervening cause and a superseding cause comes down to one word: foreseeability. Both describe an event that happens after a defendant’s negligent act but before the plaintiff’s final injury. If a reasonable person could have anticipated that event, it’s a foreseeable intervening cause, and the original defendant stays liable. If the event was so unusual or disconnected that no reasonable person would have seen it coming, it’s a superseding cause, and it cuts off the original defendant’s liability from that point forward.
In other words, every superseding cause is an intervening cause, but not every intervening cause is superseding. The label depends entirely on whether the event was predictable.
Where These Terms Fit in a Negligence Case
Negligence claims require proof that the defendant’s conduct caused the injury, both in fact and as a matter of law. Cause-in-fact asks whether the injury would have happened but for the defendant’s conduct.1Legal Information Institute. But-For Test Proximate cause is a separate limit: even if the defendant’s conduct technically caused the harm, courts won’t impose liability for bizarre or wildly unpredictable consequences.2Legal Information Institute. Direct and Proximate Cause
Intervening and superseding causes live inside the proximate cause analysis. When something happens between the defendant’s act and the plaintiff’s injury, the court has to decide whether that something keeps the defendant’s negligence connected to the harm or breaks the connection.3Legal Information Institute. Wex – Intervening Cause
What an Intervening Cause Looks Like
An intervening cause is any independent event that comes between the defendant’s negligent act and the final injury and either worsens the harm or changes how it happens. Common categories include:
- Acts of nature, like a sudden wind spreading a negligently started fire
- Third-party actions, like a second driver colliding with a car already pushed into traffic by an earlier crash
- Medical treatment errors following the original injury
- The injured person’s own later conduct, such as refusing recommended care or aggravating the injury
By itself, the existence of an intervening event tells you nothing about liability. The next question does all the work: was it foreseeable?
Foreseeable Intervening Causes Keep the Defendant Liable
If a reasonable person in the defendant’s position could have anticipated the intervening event as a natural consequence of the negligence, the chain of causation holds. The defendant is responsible for the full injury, including whatever additional harm the intervening event added.
Medical malpractice following an injury is the standard example. When you injure someone, it’s obvious they’ll need medical care, and it’s a known reality that providers sometimes make mistakes. Courts have long treated negligent medical treatment after an injury as a foreseeable intervening cause, so the person who caused the original injury can also be held responsible for harm from the subsequent medical errors.
The rescue doctrine works the same way. If someone is put in danger by a defendant’s negligence, bystanders attempting a rescue is a foreseeable response. A rescuer who gets hurt during the attempt can hold the original negligent party liable for those injuries, provided the rescuer didn’t act recklessly.
What Makes a Cause Superseding Instead
A superseding cause is an intervening event so unusual, independent, or disconnected from the original negligence that no reasonable person could have anticipated it. It supersedes the defendant’s conduct as the legal cause of the injury, meaning liability stops at the point the superseding event occurred.3Legal Information Institute. Wex – Intervening Cause Whoever caused the superseding event picks up responsibility from there.
Imagine you’re hurt in a car accident and taken to the hospital. While you’re recovering, a stranger walks into your room and assaults you for reasons that have nothing to do with the accident. You wouldn’t have been in that hospital bed without the crash, but the assault is so disconnected from the original negligence that it would likely qualify as a superseding cause. The driver who caused the accident isn’t on the hook for the assault injuries.
The line between foreseeable and superseding is where most of the real litigation happens. Reasonable people disagree about what’s predictable, which is why this question so often ends up with a jury.
Factors Courts Use to Draw the Line
Many jurisdictions follow a framework drawn from the Restatement (Second) of Torts. Courts weigh these factors differently, and no single one decides the question, but the usual considerations are:
- Whether the intervening event produced a fundamentally different kind of harm than the original negligence would have caused
- Whether the event appears extraordinary in hindsight or looks like a normal consequence of the situation
- Whether the event operated independently or whether the defendant’s negligence created the conditions that made it likely
- Whether the event was caused by another person’s voluntary, deliberate action
- Whether a third party’s conduct was wrongful, especially if it was intentional or criminal
- How blameworthy that third party was
Intentional and criminal acts by third parties lean toward being treated as superseding, but not automatically. The analysis is fact-heavy, and framing matters.
What This Means for Your Recovery
When an intervening cause is foreseeable, more than one party may share responsibility for the injury: the original defendant and whoever caused the intervening harm. How that liability gets split depends on your state’s rules.
Some states use joint and several liability, letting you recover the full amount from any single defendant, who can then seek contribution from the others. Other states use comparative fault, where each defendant pays only their percentage share. Some comparative fault states bar your recovery entirely if you’re more than 50% at fault yourself; others reduce your recovery by your share but don’t cut it off.
The practical point is that a foreseeable intervening cause doesn’t let the original defendant walk away. Their share may shrink, but they remain responsible for the harm they set in motion. A superseding cause, by contrast, does let them off the hook for anything that happens after the superseding event.
Pre-Existing Conditions Are Not Intervening Causes
Defendants sometimes try to recast a plaintiff’s pre-existing medical condition as an intervening cause. It isn’t. Under the eggshell skull rule, a defendant is liable for the full extent of the plaintiff’s injuries, even when those injuries are unexpectedly severe because of a condition the defendant didn’t know about.4Legal Information Institute. Eggshell Skull Rule A pre-existing condition didn’t intervene; it was already there. The defendant’s negligence activated it.
Who Raises Superseding Cause and When It Gets Decided
Superseding cause is a defense. The defendant raises it, essentially arguing that something so unforeseeable happened after the negligence that the negligence is no longer the legal cause of the injury. The defendant carries the burden of proving the intervening event was unforeseeable and that it, rather than the original conduct, caused the harm.
Whether an intervening force qualifies as superseding is usually a question of fact for the jury, unless the circumstances are so clear that only one reasonable conclusion is possible. Most of these disputes don’t get resolved on early motions. They go to trial, with both sides putting on evidence about what a reasonable person could have anticipated at the time of the original negligent act.