Actual cause refers to a cause or factor without which the event could not have occurred. It is also termed as but for cause or cause in fact or factual cause. The but-for test is often used to determine actual causation. But for test is one of several tests to determine if a defendant is responsible for a particular happening. The test simply asks, "but for the existence of A, would B have occurred?" If the answer is yes, then factor A is an actual cause of result B.