Tueller drill, or the 21’ rule. I’m actually teaching a civic group on my agencies use of force policy in about 3 mins.
I’ll come back and fill on details when I get home tonight.
The Tueller drill is named after Sgt. Dennis Tueller of the Salt Lake City Police Department. In 1983 he ran a series of experiments where an officer stood with a holstered (and unloaded) pistol, and another officer stood a distance away from the them. When the second officer charged the first officer, the first officer was to draw his unloaded pistol and pull the trigger. Aiming wasn’t really part of the testing, and honestly with distances involved, instinctive/point shooting is adequate. With the double action revolvers, and single retention holsters (normally thumb breaks) of the time, the distance that was found to be inside the normal officers ability to break a shot before the suspect reached the officer was 21 feet. In essence if a threat armed with a contact weapon of some kind, is inside of 21 feet, you are probably not going to be able to solve that problem with a pistol immediately. You need to add movement on your part, and unarmed techniques, to buy time to use your pistol effectively.
In the current time (we did testing on this when I was still full time range staff) the distance is about 35 feet. There are several factors for this. Holsters are much more secure, but slower. You can get on the trigger safely, sooner with a DA revolver if you know what you’re doing then a striker fired pistol (like almost all duty pistols tend to be these days). Also our police cadets may just run faster.
Ironically the takeaway a lot of officers had was 21’ feet is the danger zone, rather than figuring out what the reactionary gap in time would be. An officer who is fast, confident, and competent but slow reflexes may need 2.5 seconds, versus the officer with reflexes of an NHL goalie and only moderate pistol skills might need .8 seconds. If the suspect is a college level sprinter, the distance covered in 2.5 seconds versus .8 seconds is a major difference.
This is my professional field (LE use of force), so feel free to ask any questions, or shoot me a PM to keep this on topic.