But the best case is still to be made by a combination of eyewitness testimony and circumstantial evidence. Neither alone is conclusive, but both together can be.

An example of this may be, if I may borrow from the Kennedy assassination again, the 3 young men watching the motorcade from the windows directly and 1 floor below the "sniper's nest" window. They said they heard very loud gunshots above them; they said plaster from the ceiling fell into one fellow's hair; and the person directly below the sniper's nest window said he heard shells hit the floor and the action of a bolt-action rifle between the shots.

By itself, I suppose, one might wonder if these men are just making up a story to garner media attention. (The recent DC sniper shootings come to mind. Somebody falsely claimed to see the gunman and gave a made-up description to the police.) However, coupled with the finding of shells on the floor directly above them and the finding of a bolt-action rifle nearby combines to make a convincing argument shots were fired from that location. They physical evidence is strongest, but the witness testimony helps interpret that physical evidence.