Updated: Sep 19, 2020
Most people have heard of the Tueller Principal which states that in general, a person needs about 21 feet of separation for his or her brain to perceive the threat, draw a weapon, and get a shot off. Obviously there are a lot of variables to include lighting, situational awareness, speed of the attacker etc. I've tried this exercise and I still needed to back up as I drew my weapon in order to keep distance. People who have been stabbed report that initially they thought they were punched. This is a valuable learning point because if you do get stabbed remember that you still have a lot of fight left in you. And if you are the person using a knife, remember that targeting counts. I cover these issues and more in "Blades and Improvised Weapons" video.