Up Close and Personal
A training video that's been widely circulated, and is still used in a number of law enforcement academies all across the country, if not the world, shows someone running across a parking lot toward an officer from 21 feet away. The video demonstrates how the officer only has enough time to draw and fire one or two rounds before the assailant is on top of him.
First off, in an edged-weapon attack most people are not going to come running at you from across a mall parking lot. I'm not saying it would never happen, but it's highly unlikely. What they're going to do instead is close the distance between the two of you before they attack, so they can be effective in their attack. That's why one of the pre-attack warning signs that you've been told about since the academy is someone closing the gap on you. It's an indicator that this person may become aggressive or assaultive.
We all know, or at least we should know, that distance equals time, which equals safety. The problem with this equation is that most of the time we don't have the luxury of distance on our side. The reason the average edged-weapon attack against law enforcement takes place 10 to 12 feet away is because that's the distance we generally operate from as law enforcement officers.
In order to do your job correctly, you have to get up close and personal with the people you deal with on a daily basis. That means if you're going to make contact with someone, whether it's at a traffic stop, a domestic, or a suspicious person call, you're probably going to be the one closing the gap between you and the subject. In a perfect world you'd stay well out past the 21-foot mark, but that's not practical in the real world. So you have to have tactics that will work for the environment in which you do work. And one of these is shooting effectively from the hip.