In order to win a personal injury action, a plaintiff must prove that a defendant's negligence caused the plaintiff's injuries. In negligence law, there are two types of causation: (1) "cause in fact"; and (2) "proximate cause." The plaintiff must prove both types of causation.

A negligent act is the proximate cause of a plaintiff's injury if the injury is the natural and probable result of the act. In other words, proximate cause exists when the injury is the foreseeable result of the negligence. For example, a truck driver negligently crashes into a house. Due to the impact, a piece of plaster falls from the ceiling of a house and onto the homeowner, injuring him. The truck driver's negligence is the proximate cause of the homeowner's injury because injury to an occupant of the house is a foreseeable result of crashing a truck into the house. Note that the particular injury and the manner in which the injury occurs do not have to be foreseeable in order to constitute proximate cause. Crashing into the house is the proximate cause of the homeowner's injury because it was foreseeable that some sort of injury would occur. A second example: a bicycle rider negligently runs into a pedestrian. The pedestrian is uninjured but stunned. He walks around the block to clear his head, and he is injured by a rabid dog. In this scenario, the bicycle rider's negligence is not the proximate cause of the pedestrian's injury because being attacked by a dog is not the foreseeable result of a bicycle accident.

Concurrent Causes

When two or more negligent acts contribute to a plaintiff's injuries, those acts are called "concurrent causes." For example, a pedestrian stands on a street corner. A bicycle rider negligently runs into the pedestrian, knocking him into the street. As a truck swerves to avoid the pedestrian, a piano falls from the truck and onto the pedestrian, injuring him. Before the accident, the truck driver negligently failed to secure the piano to the truck. The negligent acts of the bicycle rider and the truck driver are concurrent causes because both acts contributed to the pedestrian's injuries.

When there are concurrent causes, both negligent actors will be liable for the plaintiff's injury only if each negligent act was a substantial factor in causing the injury. In the above example, the pedestrian's injury would not have occurred if not for the negligent acts of both the bicycle rider and the truck driver. Therefore, the negligent acts of both the bicycle rider and the truck driver were substantial factors in causing the pedestrian's injury, and both of them would be liable for damages in the pedestrian's personal injury action.

Intervening and Superseding Causes

An "intervening cause" or "superseding cause" breaks the chain of causation between a negligent act and a plaintiff's injury. For example, a truck driver negligently crashes into a house. The impact breaks a window but does not injure the homeowner. Later that night, a burglar crawls through the broken window and assaults the homeowner. The homeowner files a personal injury action against the truck driver to recover for the injuries that were inflicted by the burglar. In this case, the burglar's conduct was not a foreseeable result of the truck driver's negligence. Therefore, the burglar's conduct was an intervening or superseding cause. The truck driver's negligence was not the proximate cause of the homeowner's injuries, so the homeowner cannot recover damages from the truck driver in a personal injury action.

Copyright 2010 LexisNexis, a division of Reed Elsevier Inc.