Old Dog
Member
With all due respect, it's been refined over the years as the distance a moderately fit subject, armed with an edged weapon, could close on an armed officer, and inflict at least one fatal stabbing or slashing wound before the officer could draw from a duty holster and fire one center of mass shot.It was and is simply the average distance that an average person can run in the time that it takes a police officer to draw a handgun from an uncovered belt holster and fire once.
Later research by the FBI, among others, indicates that distance could be extended to 27 to 30 feet.
Distance is not necessarily your friend.