novus actus interveniens

An intervening act that breaks the chain of causation

Its a term used in the forensic medicine. For example in an accident case if the victim has suffered injuries due to negligence of the doctor..... Then the intervening act of the doctor is responsible for the injury and not that of the person who caused the accident.

But it does not always holds true. Its only accepted when the injury caused to the victim is reasonably foreseeable.