In law, evidence that is drawn not from direct observation of a fact at issue but from events or circumstances that surround it.
If a witness arrives at a crime scene seconds after hearing a gunshot to find someone standing over a corpse and holding a smoking pistol, the evidence is circumstantial, since the person may merely be a bystander who picked up the weapon after the killer dropped it. The popular notion that one cannot be convicted on circumstantial evidence is false. Most criminal convictions are based, at least in part, on circumstantial evidence that sufficiently links criminal and crime.