MBE Fast Fact: Actual Cause

It's likely you'll see questions on the MBE in which more than one person causes an injury to a third party, and you'll be asked to determine the liability of the parties causing the injury. This is an issue of causation, specifically actual causation. The analysis depends upon whether two (or more) parties together jointly cause the injury or instead two (or more) parties act, but only one of the parties causes the injury.

Let's examine the first scenario: Let's say x and y act jointly and cause an injury to z. The question to ask is whether x acting alone or y acting alone would have been sufficient to causes the injury to z. If, for example, x acting alone would have been sufficient to cause the injury to z, then x's conduct is the actual cause of the injury to z provided x's conduct was a substantial factor in causing the injury to z. The same analysis applies in determining whether y's conduct is the actual cause of z's injury.

A second scenario involves two acts, but where only one of the acts causes an injury. So here assume that x and y are once again involved in conduct, and z is once again injured. But here, rather than x and y jointly causing the injury to z, only one (x or y) causes the injury, but it is unknown which of the two is the cause. Here, the burden of proof shifts to the defendants (x and y) and each must show that his negligence was not the actual cause of the injury to plaintiff (z).