EDGED WEAPON DEFENSE: Is or was the 21-foot Rule Valid?

This is a two part article with two links to outside articles.

Part I
For more than 20 years now, a concept called the 21-Foot Rule has been a core component in training officers 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.

Read More about part I of this article

Part II

3. MORE DISTANCE. "In reality, the 21-Foot Rule--by itself--may not provide officers with an adequate margin of protection," says Dr. Bill Lewinski, FSRC's executive director. "It's easily possible for suspects in some circumstances to launch a successful fatal attack from a distance greater than 21 feet."
Among other police instructors, John Delgado, retired training officer for the Miami-Dade (FL) PD, has extended the 21-Foot Rule to 30 feet. "Twenty-one feet doesn't really give many officers time to get their gun out and fire accurately," he says. "Higher-security holsters complicate the situation, for one thing. Some manufacturers recommend 3,000 pulls to develop proficiency with a holster. Most cops don't do that, so it takes them longer to get their gun out than what's ideal. Also shooting proficiency tends to deteriorate under stress. Their initial rounds may not even hit."
Read More about the 21 foot rule