Intervening and Superseding Forces in Torts: What Are They, and Why Should I Care?

Every law student knows the basic elements of a negligence claim. An actor must (1) owe a victim a duty to conform to a standard of care, (2) breach that duty, and in so doing, (3) actually and (4) proximately cause the victim to suffer (5) legally cognizable harm. Of these elements, duty is surely the most involved, the most complicated, and—on the bar exam—the most crucial. But the most esoteric and inaccessible element of negligence, and thus the one most likely to trip up examinees, is proximate causation.

Proximate causation shouldn’t be confused with its less eccentric counterpart, actual causation. In most cases, actual causation asks one straightforward question—would the victim’s injury have occurred even if the actor had conformed her conduct to the applicable standard of care? If the answer is yes, actual causation fails, and with it, the victim’s negligence claim. If the answer is no, then actual causation is satisfied.

But even if actual causation is satisfied, the other elements of negligence must also be satisfied–—including proximate causation, the subject of this article. Proximate causation takes the causation inquiry a step (or 2) beyond asking whether the actor’s breach of duty was a necessary antecedent, without which the injury would not have occurred. Having established that the actor’s breach was a necessary antecedent, proximate cause goes on to question whether the causal connection between the actor’s breach and the victim’s harm is close enough to make it fair to hold the actor liable for the victim’s injury.

Courts generally frame this inquiry in terms of foreseeability. That is, courts ask whether the general type of harm that the victim suffered is a reasonably foreseeable result of the actor’s conduct. If so, proximate cause is satisfied. If not, proximate cause fails. Foreseeability doesn’t lend itself to bright-line rules. Rather, determining foreseeability is guided by common sense and experience. In that vein, there are a few common fact patterns that courts tend to analyze the same way. On the bar exam, then, it’s best to be alert for these patterns, so that when you see them, you’ll have a good idea concerning how to approach the question. We’ll cover some of these recurring fact patterns later on in the article.

Virtually every event in the universe has multiple causes. Injurious accidents are no different. Thus, if the bar examiners ask you to analyze a proximate-causation problem, there will almost always be other factors that combine with the actor’s negligence to cause the injury. These factors are called intervening forces. The dispositive legal issue in these cases is often whether the intervening cause bears such a strong and direct causal relationship to the injury that it defeats proximate causation, thereby absolving the actor of liability.

An intervening force that does not defeat proximate causation is just an intervening force. On the other hand, if an intervening force does break the causal chain and defeat proximate causation, it becomes a superseding force (sometimes called, in quainter language, a supervening force or supervening cause). Superseding forces are so named because they literally supersede the actor’s conduct and become the legal cause of the injury, freeing the actor from liability.

It’s likely that on a torts exam or the bar exam, you’ll be called upon to determine whether an intervening force is a superseding force. The distinction between a mere intervening force and a superseding force turns on foreseeability. If the intervening force is foreseeable, it’s a mere intervening force. But if the intervening force is unforeseeable, it’s likely—not definitely, but quite likely—a superseding force. 

Some common, recurring intervening forces are nearly always deemed foreseeable. Most of these have one common thread: they involve the negligence of third parties. Indeed, the negligence of others is typically deemed foreseeable. So, if a third party’s negligence combines with the actor’s negligence and contributes to or worsens the victim’s injury, it’s a sure bet that the third party’s negligence is a mere intervening force and not a superseding force. With all this in mind, let’s survey a few common examples of third-party negligence you’re likely to encounter on the bar exam.

An actor’s negligence may unreasonably yet foreseeably place the victim in a position of helpless peril. It’s usually deemed foreseeable that a third party will come along and, through negligence, injure the victim further.

To illustrate, suppose a motorist negligently strikes a pedestrian, breaking the pedestrian’s leg and leaving her helpless by the roadside. The motorist drives off, having done nothing to help the pedestrian. Shortly after, a trucker negligently veers off the road and strikes the helpless pedestrian, breaking her arm.

In this scenario, as to the motorist, the trucker’s negligence is an intervening force. Because the motorist’s antecedent negligence placed the pedestrian in a position of helpless peril, the trucker’s intervening negligence was quite foreseeable. Hence, concerning the motorist, proximate causation is satisfied as to both the broken leg and the broken arm. (Having played no role in causing the broken leg, the trucker is liable only for the broken arm.)

If the actor’s negligence places the victim in helpless peril, it’s typically deemed foreseeable that a well-meaning third-party rescuer will come along and, through her own negligence, exacerbate the victim’s injury. Thus, the rescuer’s negligence in this case is a foreseeable intervening force.

On the other hand, what if the rescuer takes some unusual or extraordinary action that creates risks differing from those generally associated with rescue efforts? In that event, the rescuer’s unusual or extraordinary action is an unforeseeable superseding force that will absolve the actor of liability, insofar as the rescuer worsens the victim’s condition. 

To illustrate, suppose a pedestrian on a highly trafficked promenade isn’t paying attention and therefore negligently bumps into a student. The student falls to the ground and hits his head on the sidewalk, fracturing his skull and rendering him unconscious. The pedestrian briskly walks away, leaving the student helpless and unconscious on the promenade.

Later on, while the student remains unconscious on the promenade, a vendor comes along and tries to move the student to a safer, less trafficked area. So doing, the vendor negligently causes the student to crack his face against the adjacent pavement, breaking several of his teeth. 

Here, the pedestrian is responsible for both the fractured skull and the broken teeth. The pedestrian’s negligence left the student helpless on the promenade. The well-meaning vendor, the rescuer in this scenario, later came along and negligently exacerbated the student’s injuries. There seems to be nothing unusual or extraordinary in the fact that the vendor, in negligently moving the student from the promenade, caused the student to hit his face against the pavement. 

But let’s change the facts a bit. Suppose that the vendor didn’t try to move the student. Instead, she espoused the belief that bloodletting was a cure for most any malady or injury, including unconsciousness arising from impact to the head. Acting in accordance with this belief, the vendor cut open the student’s forearm and exsanguinated the student. The loss of blood caused the student to permanently lose substantial mobility in his hand. Here, the vendor’s attempted “rescue” is unforeseeable, making it a superseding force that absolves the pedestrian of liability for the loss of mobility in the student’s hand. (Of course, the pedestrian remains liable for the fractured skull.) 

Oftentimes, the actor’s negligence will place the victim in need of medical assistance. If medical professionals negligently worsen the victim’s injuries, this negligence is virtually always foreseeable. Thus, proximate cause against the actor is satisfied as to any injuries caused by this intervening medical negligence. Here again, extraordinary or unusual actions by medical professionals are unforeseeable superseding forces that will absolve the actor as to any injuries caused or worsened by these actions.

Suppose a motorist negligently strikes a pedestrian, breaking his leg and foreseeably leaving him stranded by the roadside in a hot desert. By the time first responders arrive and take the pedestrian away in an ambulance, he has become severely dehydrated. At the hospital, the attending physician directs nursing staff to administer an intravenous saline solution to treat the dehydration. Instead, the nurse negligently administers a powerful narcotic, causing the pedestrian severe complications. The motorist is liable for both the broken leg and the complications attributable to the narcotics. The nurse was a medical professional treating the pedestrian for injuries traceable directly to the motorist’s negligence, and there was nothing unusual or extraordinary about the doctor’s directive to treat dehydration with a saline solution.

An actor is liable for the foreseeable ways in which third parties will react to danger that the actor negligently creates. Hence, these reactions are nearly always deemed foreseeable intervening forces.

Suppose a motorist negligently veers off the road and onto a sidewalk, heading straight toward a pedestrian. To avoid getting run down, the pedestrian dives out of the way and, in so doing, strikes a mother carrying an infant, knocking them both down. Both mother and infant sustain injuries as a result. Here, the motorist is liable for the mother’s and infant’s injuries. The pedestrian’s attempt to evade the motorist’s car seems like quite a foreseeable reaction to the motorist’s negligently driving off the road. 

Natural forces are generally treated no differently from any other intervening forces. Thus, a truly unforeseeable natural force may be a superseding cause absolving the negligent actor of liability. On the other hand, foreseeable natural forces are treated like any other foreseeable intervening forces and will not absolve the actor. 

But there’s a crucial wrinkle here. Generally, if a force of nature merely increases or accelerates the harm that would have resulted from the actor’s negligence, the force of nature is treated as a foreseeable intervening force, not a superseding one—even if the natural force’s occurrence was unforeseeable.

Suppose a deckhand on a ship is tasked with removing flammable oil from the ship’s hull. If the deckhand performs this task negligently and thereby leaves oily film on the hull, it is foreseeable that part of the ship will catch fire. One night, the deckhand does his job very negligently, leaving a substantial and flammable oily film on the ship’s hull. Later that night, an unforeseeable bolt of lightning strikes the ship, igniting the film and greatly damaging the hull. Here, true enough, the lightning was unforeseeable. But the result, fire damage to the ship’s hull, was the same type of harm that the deckhand’s negligence was likely to cause in any case. Accordingly, proximate cause is satisfied against the deckhand, even though the lightning’s occurrence was unforeseeable.

But let’s change the facts a bit. Suppose the deckhand negligently bumped into the ship’s cook, knocking her down and leaving her unconscious on the ship’s upper deck. When this accident occurs, the sky is clear. But shortly after, a freak, unforeseeable lightning storm occurs, during which a lightning bolt strikes the still-unconscious cook, causing her severe burns. As to the burns, proximate cause fails against the deckhand. It hardly seems foreseeable that someone will suffer burns due to being knocked down on the deck of a ship, and the lightning’s occurrence was unforeseeable. Accordingly, as to the burns, the lightning is a superseding force absolving the deckhand of liability.

Intervening crimes and intentional torts of third parties are normally deemed unforeseeable superseding forces. Yet 2 major exceptions exist to this rule. One applies if there was some special relationship between the actor and the victim (or between the actor and the third party), creating a duty for the actor to use reasonable care to protect the victim from third-party misconduct. The other applies if the third party’s crime or intentional tort is among the risks of foreseeable harm arising from the actor’s tort.

Suppose a guest stays overnight at a hotel, which is located in an area known for frequent, violent crime. The lock on the guest’s door is a simple household type that could easily be overcome with a credit card. That night, an assailant breaks into the guest’s room and violently attacks the guest. Assuming that the hotel’s failure to use a more robust lock is negligent, surely one foreseeable result is that a wrongdoer will break into the room and attack its occupant. Accordingly, the assailant’s attack is not a superseding force in this case.

Sometimes, a victim will suffer harm after the risk of foreseeable harm from the actor’s misconduct has abated. In that event, the abatement of the risk of harm is virtually always a superseding force absolving the actor from liability for subsequent injuries.

Suppose an excavator digs a hole in a forest and negligently fails to cover the hole or place any barrier or warning signs around it. A hunter walking through the forest at night falls into the hole and sprains his ankle, rendering him powerless to climb out of the hole. Sometime later, a camper helps the hunter out of the hole and takes him to the hunter’s cabin, which is sturdy and secure. Still later that night, a large grizzly bear breaks into the cabin and mauls the hunter. Here, the excavator is not responsible for any injuries attributable to the bear. When the camper rescued the hunter and gave him lodging in the cabin, the risk of any foreseeable harm due to the hunter being trapped in the hole had abated.

From your first day of law school to your final day of practice, Quimbee is there to help you succeed. Get up to speed with causation and a host of other torts issues with essential video lessons, essay practice exams, and multiple-choice questions. And don’t forget to explore the Quimbee Bar Review+ features students across the country rely on to help them pass the bar exam on their first attempt.