[SafetyLit note: The 21-foot rule or "Tueller Drill" is a self-defense training exercise to prepare against a short-range knife or melee attack when armed only with a holstered handgun.]
The purpose of this study was to scientifically assess the long-standing 21-foot rule. There are several anecdotal publications looking at the 21-foot rule as a standard in policing. This study uses experimental design to examine whether this standard should continue in modern-day policing. The 21-foot rule was tested in three independent experimental design studies. The first study measured the average speed at which a person could run 21 feet. The second and third studies tested the speed at which an officer could draw and fire their weapon with no stress and under stress respectively. The final study examined methods for increasing survivability for the officer (movement). The findings show the 21-foot rule to be an inadequate standard for officers to safely draw and fire their weapons when being charged by a suspect who's intent it to cause harm. Additionally, different strategies of moving can increase the officer's ability to survive.