Police departments going against the 21 foot rule

"So in our instance, the officer can simply back up — giving himself more than 21 feet. He can put something like a table or a car or even a wall between himself and the man… Anything to prevent imminent danger to himself or an innocent bystander." read more http://wsls.com/2016/03/02/the-21-foot-rule/ (they are figuring out that there might be other ways to deal with a person with knife at 21 feet besides shooting them. Those methods were figured out and well known for hundreds of years before the invention of the firearm and the dumbing down of the American people. Backing up doesn't really work, but it shows you are thinking.)