Negligence

Sometimes a plaintiff's injury results from more than one cause. For instance, suppose a defendant negligently injures a pedestrian in an automobile accident. An emergency room doctor negligently treats the plaintiff, aggravating her injury. The doctor's negligence is an "intervening cause" of the plaintiff's injury. A cause of injury is an INTERVENING CAUSE only if it occurs sub-sequent to the defendant's negligent conduct.

Just because an intervening cause exists, however, does not mean that the defendant's negligent conduct is not the proximate cause of the plaintiff's injury. The defendant remains liable if he should have foreseen the intervening cause and taken it into account in his conduct. If a defendant negligently spills a large quantity of gasoline and doesn't clean it up, he will not be relieved of liability for a resulting fire merely because another person causes the gasoline to ignite, because it is foreseeable that the gasoline might be accidentally ignited. Also, it is foreseeable that a sudden gust of wind might cause the fire to spread quickly.

Even if an intervening cause is foreseeable, however, in some situations the defendant will still be excused from liability. If the intervening cause is the intentional or criminal conduct of a third person, the defendant is not liable for this person's negligent conduct. In the example where the defendant spilled gasoline and did not clean it up, he is not responsible for the resulting fire if someone intentionally ignites the gas. Also, sometimes a third person will discover the danger that the defendant created by his negligence under circumstances where the third person has some duty to act. If the third person fails to act, the defendant is not liable. In the gasoline example, suppose the defendant, a customer at a gas station, negligently spills a large quantity of gas near the pumps. The owner of the gas station sees the spilled gasoline but does nothing. The owner of the gas station, not the defendant, would be liable if another customer accidentally ignites the gasoline.

Sometimes, however, a completely unforeseeable event or result occurs after a defendant's negligence, resulting in harm to the plaintiff. An abnormal, unpredictable, or highly improbable event that occurs after the defendant's negligence is known as a "superseding cause" and relieves the defendant of liability. For example, suppose a defendant negligently blocks a road causing the plaintiff to make a detour in her automobile. While on the detour, an airplane hits the plaintiff's car, killing the plaintiff. The airplane was completely unforeseeable to the defendant, and thus he cannot be held liable for the plaintiff's death. The airplane was a superseding cause of the plaintiff's death.

Even great jurists have had difficulty articulating exactly what constitutes proximate cause. Although the law provides tests such as "foreseeability" and "natural, direct consequences," ultimately the issue of proximate cause is decided by people's sense of right and wrong. In the example where the defendant spills gasoline and does not clean it up, most people would agree that the defendant should be liable if a careless smoker accidentally ignites the gasoline, even if they could not articulate that the smoker was a foreseeable, intervening cause of the fire.