The Tueller Drill, developed by Salt Lake City police in 1983, established the 21-foot benchmark now taught in nearly every serious defensive-tactics curriculum.
Understand how quickly distance closes so you set boundaries in time to matter.
Twenty-one feet feels like a long way. It is not. A determined attacker crosses it in roughly the time it takes you to identify the threat and respond - about a second and a half.
The lesson is not to fear crowds. The lesson is to set your boundaries early. If someone you do not know approaches inside conversational distance, speak up, angle off, put something between you.
A car door, a shopping cart, a park bench - any barrier turns 21 feet into 30 or 40, and 30 or 40 is time you can use. Distance and barriers are the same technique in two shapes.
- 1An attacker at 21 feet can reach you in about 1.5 seconds
- 2Distance is the cheapest defense available
- 3Barriers multiply distance without needing more of it
- Underestimating how fast a threat closes
- Waiting for an attacker to make the first move at close range
- Refusing to be 'rude' at the cost of your safety