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Confronting the Myth in Police-Suspect Knife Confrontations

by Derek Gilna

Each year dozens of suspects armed with knives are needlessly shot and killed by police who feel that they are justified in using deadly force based upon the “21-Foot Rule” contained in many department training manuals. According to former San Jose police officer and criminologist, Dr. Ron Martinelli, the rule has no basis in fact and should no longer be followed.

The “21-Foot Rule” apparently arose out of police training manuals formulated in Salt Lake City, and was based upon the premise that a suspect armed with an edged weapon could cover 21 feet faster than a police officer could draw and fire his holstered weapon. Based upon that theory, police officers have used it as justification to shoot suspects in the past several decades.

According to Dr. Martinelli, “I study officer involved cases every single day. I actually get notations all around the United States whenever an officer goes down or a suspect goes down.” Martinelli said that he carried out numerous drills with police officers of varied experience and skill sets and measured them against the reaction time of U.S. Navy Seals.

As a result of data collected from those drills, Martinelli said, he has determined that the distance a suspect can cover before an officer draws his weapon varies from eight feet for a Seal to 65 feet for a rookie cop, so the “Rule” is actually a myth. “And I wrote about that and that was my theory over a year ago. As long as the research is practically based, then we can take those numbers and we can put context to it and turn it into good training methodology. That’s the type of research that we need to have with law enforcement in the United States,” according to Martinelli.

Another expert and author, Dr. Franklin Zimring, a professor at the University of California at Berkeley, noted that he had reviewed thousands of confrontations between police and suspects, and found that 275 involved knives or other edged instruments.  “The threat that the police officer faces (when a suspect has an edged weapon) is not a threat to the police officer’s life,” he said. Citing the research done for his 2017 book, When Police Kill. Zimring maintained, “The number of cases we found ... of somebody with a visible weapon charging at a police officer actually killing the police officer in the United States was zero.”

FBI data show that only two police officers died in hundreds of confrontations with knife-wielding suspects in 10 years, a result confirmed by the National Law Enforcement Officers Fund data center, which noted that an average of 50,000 officers are assaulted every year.

Martinelli believes that officers confronting suspects armed with knives would be better served, and more importantly, just as safe, if they stayed further away from suspects, since even shooting a suspect might not stop him. “Unless that suspect bleeds out or unless that suspect is hit directly in the brain,” said Martinelli, “that person can continue to attack you for two or three minutes to kill you.”

He also suggested that the data and information obtained from his studies should be used to update police training to reduce threats to both police and the public. Martinelli’s research also convinced him that police officers had options in dealing with suspects and that police should be taught to step back, create distance from threats, and take cover when necessary while assessing situations. “We need to constantly retrain officers on field craft such as this,” he stated. “Teach [officers] how not to get so captured by the moment. You don’t always have to make an arrest you don’t always have to put your hands on people. If we can teach officers new skills [as a result of] this research ... we can save some lives.”

Given the number of suspects shot and killed by police officers every year, we can only hope that police departments heed the research data and prioritize the elimination or significant modification of the “21-Foot Rule” and the mentality behind it. Police departments must teach their officers that even if all confrontations with the public cannot be eliminated such confrontations need not necessarily lead to the death of the suspect. 


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