[Tenacious 1]

In what possible way can the gun used by the Customer to stop the robbers, be evidence for or against the robbers?

I don't doubt the man is a hero. He should be rewarded.

Evidence: The gun links the shooter (hero) to the scene and corroborates his testimony in the trial. He states, "It's my gun. I was there. This is what I saw." Fingerprints on the gun, some ballistics test and gunpowder residue prove forensically that whatever he says is credible.

[ApplegateRanch]

Evidence: The gun links the shooter (hero) to the scene and corroborates his testimony in the trial.

So do the brown-stained pants of the cashier...were they confiscated and locked up, too?

There is "evidence"; and there is "reasonable evidence"; then there is this kind of "reasoning": the gun has to be used to prove that this guy was there as a witness, or his testimony is no good.

Where is the similar "evidence" similarly linking ALL THE OTHER WITNESSES? Where does it end?