Police Science: The '21 Foot Rule' - Use and Misuse.
From Force Science Institute.
"In 2014, Dr. Ron Martinelli authored Revisiting the “21-Foot Rule,” wherein he rejected any suggestion that a suspect merely possessing a knife at less than 21 feet could be summarily killed. Martinelli too had heard the 21-Foot “Rule” being misstated by experts on all sides. He challenged any oversimplification of Tueller’s work and, citing Force Science research, argued that to properly assess threats required a sophisticated understanding of perception, decision making, and action.
Calibre Press, one of the most influential public safety training companies in the world, made clear in Street Survival II (2018) that, “No one should ever think, or certainly ever teach and endorse, a policy that says anyone within 21 feet of you, armed with an edged weapon, should be shot!”
And, in Chief Ken Wallentine’s The 21-Foot Principle Clarified (2018), Dennis Tueller himself confirmed that he never taught that an officer could shoot anyone with an edged or impact weapon simply for being closer than 21 feet from the officer."
Read the full article here.