How the knife can win vs the gun at close range. The 21 foot rule, also known as the Tueller Drill.

This video demonstrates some of the lesser-known mechanics of close-range combat between knife and gun.

Wikipedia:

The Tueller Drill is a self-defense training exercise to prepare against a short-range knife attack when armed only with a holstered handgun.

Sergeant Dennis Tueller of the Salt Lake City Police Department wondered how quickly an attacker with a knife could cover 21 feet (6.4 m), so he timed volunteers as they raced to stab the target. He determined that it could be done in 1.5 seconds. These results were first published as an article in SWAT magazine in 1983 and in a police training video by the same title, “How Close Is Too Close?”[1][2]

A defender with a gun has a dilemma. If he shoots too early, he risks being accused of murder. If he waits until the attacker is definitely within striking range so there is no question about motives, he risks injury and even death. The Tueller experiments quantified a “danger zone” where an attacker presented a clear threat.[3]

The Tueller Drill combines both parts of the original time trials by Tueller. There are several ways it can be conducted:[4]

  1. The (simulated) attacker and shooter are positioned back-to-back. At the signal, the “attacker” sprints away from the shooter, and the shooter unholsters his gun and shoots at the target 21 feet (6.4 m) in front of him. The attacker stops as soon as the shot is fired. The shooter is successful only if his shot is good and if the runner did not cover 21 feet (6.4 m).
  2. A more stressful arrangement is to have the attacker begin 21 feet (6.4 m) behind the shooter and run towards the shooter. The shooter is successful only if he was able take a good shot before he is tapped on the back by the attacker.
  3. If the shooter is armed with only a training replica gun, a full-contact drill may be done with the attacker running towards the shooter. In this variation, the shooter should practice side-stepping the attacker while he is drawing the gun.

MythBusters covered the drill in the 2012 episode “Duel Dilemmas”. At 20 ft (6.1 m), the gun-wielder was able to shoot the charging knife attacker just as he reached the shooter. At shorter distances the knife wielder was always able to stab prior to being shot.[5]

Cop stabbed in back, partner slow to respond

OC spray and Taser were used to take the man into custody following this. The police officer suffered a 6cm wound and survived.

An ambush gives the attacker initiative. They have had time to mentally and tactically prepare for the situation. The defender may not be psychologically prepared or have any kind of plan, and is at minimum a few seconds behind the attacker to even understand what is happening.

The cop who stood there for a few seconds either did not understand what was happening or was in a kind of denial for some time. This is not a conscious decision made while observing the situation. It is likely a result of inadequate training.

Police clear house and shoot man armed with knife

Police in this video clear a house room by room with a mix of best practice and sloppier methods (in particular brazenly opening doors and sticking their head or guns in) before they are confronted with a man who attacks with a knife. Luckily, in the last room they did not approach the closet door immediately and open it, allowing enough of a reactionary gap to avoid being stabbed.

Bystander assists cop when knife search turns into struggle

Suspect attempts to flee when a police officer searches him. As the struggle begins, a large knife can be seen tucked in to the rear of his belt. The knife falls to the ground as he escapes the grip of the cop. As the cop again grabs the suspect and pulls him to the ground, a bystander who apparently has some training in grappling assists by controlling the legs of the suspect. The bystander then transitions to a rear naked choke which effectively restrains the suspect who stops resisting.