This may not occur to everyone, but backstops are not only for the range. Around a decade ago, I stumbled into a robbery just about to unfold in a store. I suddenly realized that my only available path of retreat would take me right past the getaway driver. I was where I was. I had little realistic choice but to intervene. There were innocents milling round ahead of me who might at any moment move into my line of fire. There were people who might have walked behind the perp. My first thought was "backstop!" I quickly move to ensure a clean shot--with coolers behind the perp. He saw that and ran for the door. Shortly afterwards Kathy Jackson related a similar account. In a recent after action review of a robbery video, it was pointed out that he defender may have harmed persons and been found liable when she fired shots without knowing what was outside. And now this: we know that a shotgun fired at close range has a very tight pattern, and requires aiming. But further out, it really spreads. The shot can injure several people. In my case, were i to choose a shotgun, I would mitigate some of that risk by using slugs.