The law refers to these as superseding or intervening causes. In some states the terms are different. In other states the terms may be used more as synonyms. The point is that a superseding cause is an event, which occurs after the defendant’s original negligent act, that breaks the chain of causation.

For example, let’s say Driver A negligently rear-ends Driver B, causing injury to Driver B. An emergency crew comes to pick up Driver B to take her to the hospital for evaluation. As medical personnel take Driver B from the ambulance, a lightning bolt strikes the stretcher and kills Driver B. The lightning strike would qualify as a superseding cause that breaks the chain of causation from Driver A’s negligent driving.

Many times such intervening causes are called Acts of God. One recent example occurred in Louisiana when the owner of a building alleged that the company that leased his building had negligently attached a sign to the top of his building. During Hurricane Katrina, the sign smashed into the building and caused significant damage. The owner of the building sued the company that leased his building, contending that the improper attachment of the sign caused the damage. A Louisiana appeals court disagreed in Duboue v. CBS Outdoor (La.App. 2008; see LegalSpeak above), finding that the damage from Hurricane Katrina was an act of God that broke the chain of causation.