What does the 21-foot "rule" demonstrate regarding distances in threats?

The 21-foot "rule" illustrates the distance a suspect can potentially cover in the time it takes for an officer to respond, particularly in situations involving a lethal threat. This concept highlights the critical time disadvantage officers face when confronted with an armed suspect. It suggests that within approximately 21 feet, a suspect can reach an officer before the officer has sufficient reaction time to respond effectively, especially if the suspect is armed with a knife or similar weapon. This understanding is vital in ensuring that officers are aware of their surroundings and can take appropriate action to protect themselves when confronting potential threats. The 21-foot distance serves as a benchmark in training and situational awareness, emphasizing the importance of proactive measures and maintaining a reactionary gap when dealing with suspects.