The number isn't plucked out of thin air and has some variance due to factors such as reaction speed and speed of the runner, but it's an average. 21 feet is a good "rule of thumb" but isn't an exact measurement of "safe distance". You could have a bit more distance - you could have less. It's a rule of thumb.
>Tueller Drill departs from the premise that you can only use your hand gun. This attitude is part of the problem.
TASER guns have a single shot. I wouldn't risk my life on me hitting my target in a single shot. Stunguns require proximity.
For pepperspray, would you bet your life on an 85% chance of something working? OC spray is not 100% effective and some people are straight up immune to the spray. AFAIK, humans are not immune to bullets.
I'd advocate for the use of the above non-lethals in reliable scenarios where the officer is concerned about possible escalation but does not yet feel to be in mortal danger. Which isn't many scenarios and draws into question if force was needed at all. Many non-lethal actions seem to be punished more than lethal actions, because "if force was necessary it should have only required lethal force if their life was in danger".
Which brings me back to the "legitimate danger" vs "public concept of danger" issue...
If you want more non-lethal options to be used, the justification of using them needs to be realistic - which involves educating the public on what is and isn't a dangerous/escalating scenario. I don't see that happening anytime soon, which is unfortunate.
