If you’ve been to a gun training course you have probably heard of the 21 foot rule that relates to the distance between an adversary with a knife and you, an armed citizen. It’s called the Tueller Rule.
The Tueller Drill is a self-defense training exercise to prepare against a short-range knife attack when armed only with a holstered handgun.
Sergeant Dennis Tueller, of the Salt Lake City, Utah Police Department wondered how quickly an attacker with a knife could cover 21 feet (6.4 m), so he timed volunteers as they raced to stab the target. He determined that it could be done in 1.5 seconds. These results were first published as an article in SWAT magazine in 1983 and in a police training video by the same title, “How Close is Too Close?”
A defender with a gun has a dilemma. If he shoots too early, he risks being accused of murder. If he waits until the attacker is definitely within striking range so there is no question about motives, he risks injury and even death. The Tueller experiments quantified a “danger zone” where an attacker presented a clear threat.
The Tueller Drill combines both parts of the original time trials by Tueller. There are several ways it can be conducted:
- The attacker and shooter are positioned back-to-back. At the signal, the attacker sprints away from the shooter, and the shooter unholsters his gun and shoots at the target 21 feet (6.4 m) in front of him. The attacker stops as soon as the shot is fired. The shooter is successful only if his shot is good and if the runner did not cover 21 feet (6.4 m).
- A more stressful arrangement is to have the attacker begin 21 feet (6.4 m) behind the shooter and run towards the shooter. The shooter is successful only if he was able take a good shot before he is tapped on the back by the attacker.
- If the shooter is armed with only a training replica gun, a full-contact drill may be done with the attacker running towards the shooter. In this variation, the shooter should practice side-stepping the attacker while he is drawing the gun.
The Squirrel says: MythBusters covered the drill in the 2012 episode “Duel Dilemmas”. At 20 ft (6.1 m), the gun-wielder was able to shoot the charging knife attacker just as he reached the shooter. At shorter distances the knife wielder was always able to stab prior to being shot.
However, the Force Science Research Center at Minnesota State University-Mankato has responded by reexamining the 21-Foot Rule, and after testing the Rule against FSRC’s landmark findings on action-reaction times and conferring with selected members of its National and Technical Advisory Boards, the Center has reached these conclusions, according to Executive Director Dr. Bill Lewinsky (more here):
- 1. Because of a prevalent misinterpretation, the 21-Foot Rule has been dangerously corrupted.
- 2. When properly understood, the 21-Foot Rule is still valid in certain limited circumstances.
- 3. For many officers and situations, a 21-foot reactionary gap is not sufficient.
- 4. The weapon that officers often think they can depend on to defeat knife attacks can’t be relied upon to protect them in many cases.
- 5. Training in edged-weapon defense should by no means be abandoned.
These factors and others can impact the validity of the 21-Foot Rule because they affect an attacking suspect’s speed in reaching the officer, and the officer’s speed in reacting to the threatening charge.
The 21-Foot Rule was formulated by timing subjects beginning their headlong run from a dead stop on a flat surface offering good traction and officers standing stationary on the same plane, sidearm holstered and snapped in. The FSRC has extensively measured action and reaction times under these same conditions. Among other things, the Center has documented the time it takes officers to make 20 different actions that are common in deadly force encounters. Here are some of the relevant findings that the FSRC applied in reevaluating the 21-Foot Rule:
 | Once he perceives a signal to do so, the AVERAGE officer requires 1.5 seconds to draw from a snapped Level II holster and fire one unsighted round at center mass. Add 1/4 of a second for firing a second round, and another 1/10 of a second for obtaining a flash sight picture for the average officer. |
| The fastest officer tested required 1.31 seconds to draw from a Level II holster and get off his first unsighted round.The slowest officer tested required 2.25 seconds. |
| For the average officer to draw and fire an unsighted round from a snapped Level III holster, which is becoming increasingly popular in LE because of its extra security features, takes 1.7 seconds. |
| Meanwhile, the AVERAGE suspect with an edged weapon raised in the traditional “ice-pick” position can go from a dead stop to level, unobstructed surface offering good traction in 1.5-1.7 seconds. |
The “fastest, most skillful, most powerful” subject FSRC tested “easily” covered that distance in 1.27 seconds. Intense rage, high agitation and/or the influence of stimulants may even shorten that time, Lewinski observes.
Even the slowest subject “lumbered” through this distance in just 2.5 seconds.
Bottom line: Within a 21-foot perimeter, most officers dealing with most edged-weapon suspects are at a decided – perhaps fatal – disadvantage if the suspect launches a sudden charge intent on harming them. “Certainly it is not safe to have your gun in your holster at this distance,” Lewinski says, and firing in hopes of stopping an activated attack within this range may well be justified.
This video supports the 21-ft Rule but is interesting because it examines the reaction times at a few distances.