A more thorough explanation:

Definition: Efficient proximate cause is a legal term that refers to the primary cause of an event or injury that is legally sufficient to result in liability. It is the cause that directly produces the event and without which the event would not have occurred.

Example: A person is driving a car and runs a red light, causing a collision with another car. The efficient proximate cause of the collision is the driver running the red light. Even if there were other contributing factors, such as a malfunctioning traffic light or the other driver being distracted, the driver who ran the red light would still be held liable for the accident.

This example illustrates that efficient proximate cause is the primary cause that is legally sufficient to result in liability, even if there are other contributing factors.