Legal Definitions - efficient intervening cause

Definition: An event that comes between the initial event in a sequence and the end result, thereby altering the natural course of events that might have connected a wrongful act to an injury.

Example: A driver runs a red light and hits a pedestrian. The pedestrian is taken to the hospital and is being treated for their injuries. However, while in the hospital, the pedestrian falls out of bed and breaks their arm. The fall is considered an efficient intervening cause because it altered the natural course of events that would have connected the driver's wrongful act to the pedestrian's injury.

This example illustrates how an efficient intervening cause can break the chain of causation between a wrongful act and an injury. In this case, the driver may not be held liable for the pedestrian's broken arm because the fall was an efficient intervening cause that was not foreseeable.