A scientific study on the legitimacy of a training drill called the “21-Foot-Rule” has revealed that a practice police department across the country have used for decades is “responsible for thousands of unnecessary deaths.”

The investigation conducted by NBC Bay Area looked into how many deaths have resulted from the current policies regulating how officers are taught to deal with citizens who appear to be wielding knives.

The “21-Foot-Rule” was created in the 1980s and based on the belief that an individual holding a knife, or another sharp object, could cover 21 feet of ground in the same time it takes a police officer to draw and fire a holstered weapon. But while the so-called rule became common policy, it had never been scientifically tested.

After reviewing hundreds of cases in which police encountered suspects with knives or sharp weapons, UC Berkeley Law School Professor, Dr. Zimring, came to the conclusion that “the 21-Foot-Rule exists only as an urban legend.”

“The threat that the police officer faces (when a suspect has an edged weapon) is not a threat to the police officer’s life,” Zimring told NBC, noting that according to his research, the number of cases in which “somebody with a visible weapon charging at a police officer [and] actually killing the police officer in the United States was zero.”

Criminologist and former police officer, Dr. Ron Martinelli, told NBC that after running hundreds of drills and testing a variety of officer skill sets over the last year, he also came to the conclusion that the “21-Foot-Rule” was much more of a “myth” than an actual rule.

“It is. And I wrote about that and that was my theory over a year ago,” Martinelli said. “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.”

Martinelli argued that in addition to removing the “21-Foot-Rule” from all officer training, police officers should instead be trained to “slow down, create distance and find cover” when dealing with suspects they believe are armed.

“We need to constantly retrain officers on field craft such as this,” Martinelli said. “Teach them 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 by this research…we can save some lives.”

According to the investigation, although FBI statistics show that there is an average of around 56,000 reported assaults on police officers each year, “the numbers show that fatal knife attacks in which suspects charge police from a distance of 20 feet or more, just do not happen.” In fact, over the last 10 years, only two police officers have been killed by knife attacks, and both cases were in close quarters.

As reported, there have been multiple instances where police officers opened fire on an individual from afar, after they apparently mistook a man holding a wallet or a man holding a cellphone for a man with a dangerous weapon.

Under the “21-Foot-Rule,” those shootings are justified. However, the idea that police officers are being trained to shoot a suspect from up to 21 feet away based on the belief that they think the suspect may be holding a knife or a sharp object is absurd, and the fact that police departments across the country have used a method for decades that has no scientific research behind it, results in the opposite of “protecting and serving” the public.