The Scientific Basis for the 21-foot Rule in Police Shootings

Yesterday, the murder trial of North Carolina police officer Michael Slager for shooting Walter Scott, an African-American man fleeing from him, ended in a hung jury. 1/ Police (and their lawyers in cases in which officers face charges for unjustified shootings) sometimes refer to a “21-foot rule.” It is a rule of thumb that holds that “a suspect armed with an edged weapon [can] fatally engage an officer armed with a handgun within a distance of 21 feet.” 2/

According to one law review article, one Court of Appeals, in Sigman v. Town of Chapel Hill, held that a per se rule allowing police to shoot armed suspects within a 21-foot radius is constitutionally reasonable. 3/ Another law professor claims that police are generally trained “that they are permitted to shoot anyone who appears threatening or challenges them within that danger zone.” 4/

The legal or training “rule,” if there is one, has little bearing in a case in which a suspect is running away from the officer, but what of the underlying factual premise? Was the expert for the defendants in Sigman correct in testifying that “studies ... have shown that an armed individual within twenty-one feet of an officer still has time to get to the officer and stab and fatally wound the officer even if the officer has his weapon brandished and is prepared to or has fired a shot"? What studies have been conducted under what conditions?

The answer seems to be that no systematic body of scientific research exists and that no study at all addresses the danger zone for an officer with a weapon out and prepared to fire. At least, this is the conclusion of one police trainer as of 2014. Ron Martinelli explains that

The 21-foot rule was developed by Lt. John Tueller, a firearms instructor with the Salt Lake City Police Department. Back in 1983, Tueller set up a drill where he placed a "suspect" armed with an edged weapon 20 or so feet away from an officer with a holstered sidearm. He then directed the armed suspect to run toward 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 him.

After repeating the drill numerous times, Tueller—who is now retired—wrote an article saying it was entirely possible for a suspect armed with an edged weapon to fatally engage an officer armed with a handgun within a distance of 21 feet. The so-called "21-Foot Rule" was born and soon spread throughout the law enforcement community.

Martinelli adds that although “Lt. John Tueller did us all a tremendous service in at least starting a discussion and educating us about action vs. reaction and perception-reaction lag, ... it is certainly time to move forward with a far more scientific analysis that actually seeks to support or reject this hypothesis.” Moreover, a scientifically informed rule of thumb would have to attend to a few variables known to the officer. As Martinelli observes,

Whether the "21-Foot Rule" is an applicable defense in an officer-involved shooting actually depends upon the facts and evidence of each case. The shooting of a knife-wielding suspect at less than 21 feet by an experienced, competent, and well-equipped officer who has the tactical advantage of an obstruction such as a police vehicle between herself and her attacker might be inappropriate. But the shooting of a knife-wielding assailant at more than 21 feet by an inexperienced officer, wearing a difficult holster system, with no obstructions between herself and the attacker might be justified.

Notes

1. Mark Berman, Mistrial Declared in Case of South Carolina Officer Who Shot Walter Scott after Traffic Stop, Wash. Post, Dec. 5, 2016.
2. Ron Martinelli, Revisiting the "21-Foot Rule", Police, Sept. 18, 2014.
3. Nancy C. Marcus, Out  of Breath and Down to the Wire: A Call for Constitution-Focused Police Reform, 59 Howard L.J. 5, 50 (2016) (citing Sigman v. Town of Chapel Hill, 161 F.3d 782 (4th Cir. 1998)). With respect to the 21-foot rule, however, the court of appeals held only that a muncipality cannot be held liable for “deliberate indifference to or reckless disregard for the constitutional rights of persons” in teaching its officers “that an officer may use deadly force to stop a threatening individual armed with an edged weapon when that individual comes within 21 feet.” 161 F.3d at 23.
4. Eric Miller, Rendering the Community, and the Constitution, Incomprehensible Through Police Training, Jotwell, Nov. 10, 2016.