All evidence in a criminal court case falls into one of two categories: direct or indirect. Indirect evidence—also called circumstantial evidence—is evidence that does not directly prove the fact that is in question, but rather serves as evidence of another fact (or group of facts) from which the fact in question may be concluded.
Direct evidence, on the other hand, directly proves the fact that the jury is to decide upon.
To illustrate the difference between indirect or circumstantial evidence and direct evidence, consider the following example: a surveillance camera on a street corner captures video of a mugger attacking a man and stealing his wallet. The video is considered direct evidence because it directly proves the fact that the assailant mugged the victim.
In another case, a surveillance camera positioned above an ATM captures video of a man pulling out cash from the machine while a suspicious-looking person loiters behind him. The video shows the man finish his transaction and place the cash in his pocket before walking away. As soon as the man turns and starts walking, the video shows the loiterer push the man into an alley and follow behind him. A few seconds later, the video shows the loiterer walk out of the alley and stuff a handful of cash into his pocket. A few seconds after that, the other man comes stumbling out from the alley, clearly distressed and doubled over as if he’s been attacked.
In this case, the surveillance footage would be considered indirect or circumstantial evidence, because it does not directly prove that the loiterer attacked the man. Rather, it shows evidence of a group of facts from which it could be inferred that the loiterer mugged the man.