A professional with a knife could kill you, starting from 30 feet away, before you could draw your weapon. Working in a prison has made me much more fearful of a knife over any gun.
The idiots who decided on 21 feet have obviously never been in battle.
What would you consider an appropriate distance in determining an imminent threat? 30 feet? 50? I can hit a man sized target with a pistol at 50 yards, thats 150 feet. There had to be a reasonable distance set, too close and the law is useless, it allows the attacker to get too close. Too far and it would allow some nutjob with a rifle to go on a sniping spree. 21 feet, for ordinary everyday life, is a reasonable distance.
I've no doubt about the lethality of a thrown knife at 30 feet, but I'm wondering on the chance of encountering one of these knife throwing criminals in day to day life. There would seem to be a greater chance of a knife armed assaliant planning to get up close and personal rather than throwing his weapon at you.
As far as the "never been in battle" part ... this ranks in the top 10 of the most retarted things I've read today. The law wasnt made for battle, it was made for civilians, in everyday life. It was made to take the guesswork out of "Is this a imminent threat or not?". Inside 21 feet and behaving in a threatening manner, yes, it is a threat. 22 feet? Take a step closer.