Is The "21 Foot Rule" Valid?
For more than 20 years now, a concept called the 21-Foot Rule has been a core component in training [police] officers [in the U.S.] to defend themselves against edged weapons.
Originating from research by Salt Lake City trainer Dennis Tueller and popularized by the Street Survival Seminar and the seminal instructional video "Surviving Edged Weapons," the "rule" states that in the time it takes the average officer to recognize a threat, draw his sidearm and fire 2 rounds at center mass, an average subject charging at the officer with a knife or other cutting or stabbing weapon can cover a distance of 21 feet.
The implication, therefore, is that when dealing with an edged-weapon wielder at anything less than 21 feet an officer had better have his gun out and ready to shoot before the offender starts rushing him or else he risks being set upon and injured or killed before he can draw his sidearm and effectively defeat the attack.
Recently a Force Science News member, a deputy sheriff from Texas, suggested that "it's time for a fresh look" at the underlying principles of edged-weapon defense, to see if they are "upheld by fresh research."
Read more here.