a book I have by Michael Martin on Concealed Carry it quotes the Tempe Study, regarding an attacker being shot in the back and says that 2/10s of a second the BG could complete that movement of turning and the defender might require 5/10 of a second to stop shooting.
Yes, thanks - that is the kind of thing I was remembering. I didn't read that book or the Tempe Study, but it sounds like it parallels the material I read. I have been swamped and haven't had a chance to find a link. These kind of findings, along with the scenario of a fleeing person taking pot shots over their shoulder, make it plain that is an oversimplification to think that you can't shoot someone in the back in self defense.