Few concepts in law enforcement training are as widely recognized (or as frequently misunderstood) as the Tueller Drill.
Often associated with the so-called “21-foot rule,” the Tueller Drill was never intended to establish a universal distance at which an officer should use force. Instead, it was developed to demonstrate a fundamental problem faced by police officers: a person armed with a contact weapon can cover a surprisingly large distance in the time it takes an officer to recognize a threat and respond.
Understanding where the Tueller Drill came from helps explain why it remains relevant more than four decades later.
Where Did the Tueller Drill Come From?
The concept originated with Dennis Tueller, then a firearms instructor with the Salt Lake City Police Department.
In the early 1980s, Tueller began examining a deceptively simple question: How quickly could a person armed with a knife or other contact weapon cover the distance separating that person from an officer?
Tueller timed people moving through a distance of seven yards, or 21 feet. His experiments indicated that an average healthy adult could cover that distance in roughly 1.5 seconds.
That number was significant because approximately the same amount of time could be required for a trained officer to recognize the situation, draw a handgun from a duty holster and accurately engage a target.
Tueller discussed his findings in a March 1983 S.W.A.T. Magazine article titled “How Close Is Too Close?”
The concept subsequently became one of the best-known exercises in law-enforcement firearms and officer-safety training.
Why 21 Feet?
There is nothing magical about 21 feet.
Seven yards was already a common distance in firearms training, and Tueller's experiments demonstrated that an attacker could cross that distance remarkably quickly.
The significance wasn't the exact number. It was the relationship between distance and reaction time.
An officer encountering someone with a contact weapon may have to perceive what is happening, recognize the threat, decide how to respond and physically carry out that response. Meanwhile, an attacker who has already decided to move has the advantage of initiating the action.
That difference between action and reaction is at the heart of the Tueller concept.
The “21-Foot Rule” Isn't Really a Rule
Over time, the Tueller Drill became popularly known as the “21-foot rule", but that's potentially misleading.
Tueller himself has said that “21-foot rule” was not terminology he used. His original work dealt with recognizing a potential danger zone and emphasized concepts such as awareness, distance, obstacles and cover.
Twenty-one feet therefore shouldn't be interpreted as an automatic boundary between a safe and dangerous situation, nor does someone's presence within 21 feet by itself determine whether the use of force is appropriate or legally justified.
Real encounters involve many variables.
An individual's behavior, whether a weapon is present, the type of weapon, physical obstacles, available cover, relative positioning, the officer's equipment and numerous other circumstances can affect the situation.
Someone farther than 21 feet away could potentially present an immediate threat under certain circumstances, while someone standing considerably closer might present no threat at all.
The Tueller Drill is better understood as a demonstration of reaction time than as a rigid rule about distance.
What Does the Tueller Drill Demonstrate?
Perhaps the most important lesson of the drill is how quickly circumstances can change.
Twenty-one feet may sound like a substantial distance when two people are standing still. Once one person begins moving rapidly toward the other, however, that distance can disappear in seconds.
The drill also illustrates an important distinction between action and reaction.
The person initiating an action already knows what he or she intends to do. The person responding must first perceive the action and determine how to respond, and that takes time.
For law-enforcement officers, the broader lesson is therefore not simply about drawing a firearm quickly. Situational awareness, positioning, maintaining appropriate distance and recognizing potential threats early can all be important components of officer safety.
How the Concept Influenced Police Training
The Tueller concept became widely known throughout American law enforcement and defensive-firearms training.
Training exercises based on the concept have been used to demonstrate how rapidly an attacker can close distance and how difficult it can be to respond to a sudden close-range attack.
The discussion surrounding the drill has also evolved.
Modern instructors frequently emphasize that officers shouldn't treat 21 feet as a mathematical formula for determining when force should be used. Instead, distance is one element of a much larger assessment of an encounter.
That distinction is especially important because the phrase “21-foot rule” can create the impression that a universal legal standard exists when it does not.
More Than a Firearms Drill
One of the most interesting aspects of the Tueller Drill is that its most enduring lesson isn't necessarily about firearms. It's about time.
An officer who recognizes a potentially dangerous situation earlier has more time to make decisions. Distance can provide time. Physical barriers can provide time. Good positioning can provide time.
Conversely, allowing an uncertain situation to develop at extremely close range may dramatically reduce the amount of time available to respond if circumstances suddenly change.
Seen from that perspective, the Tueller Drill is as much an exercise in awareness and decision-making as it is a firearms-training concept.
A Concept That Still Matters
More than 40 years after Dennis Tueller published “How Close Is Too Close?”, the basic observation behind his experiment remains remarkably easy to understand.
People can cover short distances very quickly, and human reaction takes time. And distance that appears substantial while everyone is standing still can disappear almost instantly once someone begins moving.
The enduring value of the Tueller Drill isn't found in treating 21 feet as an absolute rule. It's in understanding the relationship between distance, movement, perception and reaction time.
That simple lesson helped change the way generations of law-enforcement officers thought about close-range threats, and explains why the Tueller Drill remains part of the conversation about officer safety today.