banner ad
Experts Logo


The "21 Foot Rule" - Forensic Fact or Fantasy?

By: Dr. Ron Martinelli
Tel: (951) 719-1450
Email Dr. Martinelli

View Profile on

Officers throughout the United States and perhaps internationally have heard use of force instructors discuss the "21 Foot Rule" during their officer safety, firearms and deadly force training. As both a use of force instructor and practicing forensic police practices expert, I have also trained and testified to this concept myself.

However, I don't think that the concept's founder, police Lt. John Tueller (Ret.) would have ever imagined when he designed this simple firearms training drill in the early 1980's that it would eventually become a set in stone police doctrine that is taught and testified to hundreds of times a year. The question I pose to you is, "Is the '21 Foot Rule' a forensic fact or a police myth?" My answer is, "Well that depends." But depends upon what? Well, there's the rub.

In my practice I deal with forensic facts whether I am consulting on a case or training officers to protect themselves and others. I endeavor to offer forensic solutions, not speculation in cases; especially those involving deadly force, which is my specialty. If we are dealing with critical issues of officer safety and deadly force, it is important to peel back the layers of the onion to get to the factual basis of any tactic which is presented as "doctrine" to see if it can be forensically defended during training and in court.

It is important to keep in mind that firearms instructor John Tueller designed his "21 Foot Rule," simply as a training device to assist his officer students to better understand the concept of "The Reactionary Gap." The reactionary gap is a human factors formula that compares action versus reaction. Given the fact that action is always faster than reaction, the closer an assailant is to an officer, the less time the officer has to defensively react to any aggressive action the assailant makes.

Tueller set up a drill where he placed a "suspect" armed with an edged weapon twenty or so feet away from an officer with a holstered sidearm. He then directed the armed suspect to run towards the officer in attack mode. The training objective was to determine whether the officer could draw and accurately fire upon the assailant before the suspect stabbed them. After repeating the drill numerous times, then Sgt. Tueller wrote an article wherein he opined that it was entirely possible for a suspect armed with an edged weapon to successfully and fatally engage an officer armed with a handgun within a distance of twenty-one feet. Hence, the "21 Foot Rule" concept was born and soon spread throughout the law enforcement community almost like a virus.

It is also important to keep in mind that by all accounts I have researched, Tueller's 21 foot was only a drill and was never designed nor produced as an organized, outlined and implemented research project involving the applied sciences of psychophysiology, physics, and related human factors. No forensic testing, examination, reconciliation of data, or scientific oversight of a research model was ever conducted. Further, to my knowledge, the drill and the articles leading to the development of the "21 Foot Rule" concept was never peer reviewed by certified, credentialed and/or court qualified experts in human factors applied science.

During the past thirty years since the "21 Foot Rule" has become informal doctrine within the law enforcement community, I have heard it misrepresented and bastardized by self-appointed use of force, firearms and police practices "experts" from all sides. I actually reviewed the fact pattern of an officer-involved shooting (OIS) case where an officer with a carbine fatally shot/killed a suspect armed with a knife from a distance of over 150 feet, who attempted to use the "Tueller Drill" as his defense.

Instructors and "experts" also seem to have forgotten that the original premise of Tueller's drill was that his designed circumstance involved an officer with a holstered sidearm drawing and accurately firing his weapon. In most OIS's I review, the officer already has his gun not only out of its holster but in either the "low ready" position, or directly aimed at the suspect armed with a knife, or who is furtively reaching into their waistband.

So what are the real forensic facts that might assist officers with their officer safety and deadly force determinations? Actually, there are no forensically proven facts that I am aware of that specifically verify or conclusively establish that a suspect armed with an edged weapon will more likely than not be able to seriously injure or kill an officer armed with a sidearm on all occasions and circumstances. The truth is that the "21 Foot Rule" should not be considered to be an absolute rule at all because they are too many variables involved at this point to call it a "rule." Let's discuss them.

Psychophysiology - Is the merging of the sciences of psychology and physiology. Let's keep this simple. Peer reviewed research and science tells us that humans possess both a forebrain and a midbrain. The forebrain is where cognitive processing and decision making takes place. The midbrain is where subconscious and ingrained memories take place. It is important to understand that absolutely no cognitive processing takes place in the midbrain.

When a human (officer) experiences a phobic scale response (threat/fear), on average it takes about .58 second to experience the threat and determine if it is real. It then takes about .56 - 1.0 seconds to make a response decision. In animals there are only two: fight or flight; but in humans we have five: defend (fight), disengage (retreat), posture (yell, point a finger, act aggressive), become hypervigilant (panic, confusion, freezing, using force excessively), and submit (surrender).

When a human is threatened, the brain automatically infuses the body with "survival chemicals" such as adrenalin (stimulant), endorphins (pain blockers) and dopamine (euphoric pain blocker). While the body designed these chemicals to help us survive by making us faster, stronger and more pain tolerant, they can also significantly diminish our human performance under intense stress. This ultimately affects our survival.

Under the intense stress normally associated with deadly force threat scenarios and while under the influence of survival chemicals, the body's basal metabolic rate (BMR) measured by heart rate, blood pressure and respiration, climbs significantly in milliseconds. This circumstance causes officers to classically present with perceptual narrowing ("tunnel vision"), loss of near sight vision, and auditory occlusion (diminished or total loss of hearing.) Since 66% of all OIS occur in diminished, low or no light conditions, an officer's vision can be further impaired.

Equipment and competency as reaction factors - The safety equipment an officer is attired with and the environment the deadly force confrontation takes place in are all critical factors that can impact an officer's survival against a suspect armed and attacking with an edged weapon. For instance, an officer or detective whose sidearm is secured in a Threat Level III holster will certainly have a slower draw to target acquisition time than an officer drawing from a Threat Level I holster. An officer's experience and competency with their holster system and combat shooting style are also critical human factors in an officer's ability to draw, move off the line of attack and direct accurate fire upon an armed assailant. My non-scientific studies have shown that depending upon the holster system used and the competency of the officer, it can take anywhere from 1.5 to 3.5 seconds for an officer to access, draw, move and acquire a moving target. And, they have not even fired yet! A colleague of mine lost his life during a bank robbery in part because he had not practiced with the shoulder holster he had recently purchased and was too slow to draw and engage the armed robber. Practice and proficiency matter in any high-risk encounter.

Accuracy of fire at close distances - Firearms training studies have shown that while the average officer in static firearms qualifications (non-timed standing and shooting without moving) can hit the 9-10 rings 95% of the time. However, research of actual OIS incidents has shown that officers can only accurately hit their moving assailants only 14% of the time in life or death situations from distances of only two to ten feet! So the psychophysiological components of actual gun fighting play a critical role in an officer's survivability within relatively close distances.

Start shooting to stop shooting. "Perception lag time" - Once the average officer gets on target, it takes them approximately .56 seconds to make a decision to commence shooting. However, it then takes that same officer about .33 seconds per trigger pull to fire. As the deadly force scenario rapidly evolves, it takes that same officer on average approximately .55 - .58 seconds to realize that the threat has passed and to stop shooting. This is because of a psychophysiological dynamic referred to as "perception action - reaction lag time." This is a main reason why action is always faster than reaction. The subject of why suspects are found to have entry wounds in their sides and backs when an officer has asserted that the suspect was facing them when they fired is a bi-product of perception action - reaction lag time.

Adding it all up - fantasy or forensic fact - The fields of contemporary police practices and applied sciences are rapidly changing environments. Applied science by its nature is an environment that constantly questions hypothesis and theories and is resolved to reconcile scientific statements, facts and evidence to establish the forensic facts of a matter. However, law enforcement is more inclined to be archaic and married to non-forensic, speculative dogma that is unchallenged but widely accepted as "fact."

In the immediate case of my initial analysis of the "21 Foot Rule," I would opine that Lt. John Tueller did us all a tremendous service in at least starting a discussion and educating us in the concepts of action versus reaction and perception - reaction lag time. This has certainly saved many lives within our ranks. However, it is certainly time to move forward with a far more scientific analysis that actually seeks to confirm this hypothesis that is far from "doctrine."

The truth be told, whether or not the "21 Foot Rule" is an applicable defense in an officer-involved shooting actually depends upon the facts and evidence of every unique and rapidly evolving deadly force encounter. It is certainly debatable. In some circumstances, shooting at similar distances with far more experienced, competent and better equipped officers, within an environment with physical obstructions such as a police vehicle, might be inappropriate. Whereas, with inexperienced officers, wearing a difficult holster system and no obstructions within distances greater than twenty-one feet might be justified. Just some "forensic food" for thought. Be safe out there!

Note: Special thanks to forensic expert team members Homicide Lt. Bob Prevot (Ret.), M.A., ballistic scientist/firearms expert Lance Martini, M.S., firearms expert Larry Nichols, and NSW operational psychologist and psychiatry professor Douglas Johnson, Ph.D. for peer reviewing this article.

Dr. Ron Martinelli, Ph.D., B.C.F.T., C.L.S., is a former Criminal Justice Training Center Director and current Police / Corrections Practices, Criminal Investigations and Use of Force Instructor with a unique combination of extensive field experience and academic credentials that attorneys, judges and juries appreciate and commend.

©Copyright - All Rights Reserved


Related articles


8/25/2002· Police Practices & Procedures

Law Enforcement Experts - The Underused Defense Weapon

By: Michael Levine

During my 25-year career in Law Enforcement, working for four Federal law enforcement agencies - IRS Intelligence, BATF, Customs and DEA - I never lost a prosecution case. Here's the "secret" to my success


2/15/2012· Police Practices & Procedures

Murder or Stress-Induced Hypervigilance? Officer Johannes Mehserle and the Infamous "BART Shooting"

By: Dr. Ron Martinelli

On November 5, 2010, Superior Court Judge Hon. Robert Perry sentenced former BART Police Officer Johannes Mehserle to two years in state prison for the January 1,2009, accidental shooting death of 22-year-old Oscar Grant at the Fruitdale BART station.


11/15/2013· Police Practices & Procedures

Fear & Deadly Force: Officer Involved Shootings

By: Michael Levine

The rules governing the use of deadly force by law enforcement are as easy to understand as the rules for three-card monte but about as difficult to apply as brain surgery.

; broker Movie Ad

Follow us

linkedin logo youtube logo rss feed logo