Any action has consequences that arise naturally and continuously. This basic law of cause and effect is at the root of proximate cause. Proximate cause is a term used in personal injury law referring to the act that initiates the series of events resulting in the injury; the injury would not have occurred if the act had not. It is the cause and the injury is the effect. In personal injury law, an individual is responsible for an injury if he or she is responsible for the negligent act that brought about the injury. It is best illustrated with an example.

Robert makes a pile of snowballs in his front yard. A stranger walking by picks up a snowball and throws it at a car, causing it to crash. In this case, even though Robert made the snowballs, he was not the proximate cause of the car accident. The stranger’s act of throwing the snowball is the proximate cause of the injury and he would likely be liable for any resulting damages.

An intervening cause alters the natural course of events. The presence of an intervening cause, because it changes the natural progression of events, can lessen or eliminate the culpability of a prior actor. In the prior example, the stranger’s action is an intervening cause and consequently, Robert is not responsible for an injury resulting from his act. The stranger’s action is the proximate cause of the accident and also an intervening cause, separating Robert’s actions from the accident.

In order for one to be responsible for injuries and damages in a car accident, his or her negligence must be the proximate cause of those injuries and damages, without the presence of any intervening causes, altering the natural course of events. Because of this, the presence of an intervening cause is a potential defense in a car accident lawsuit alleging negligence.