UNSUB - you said: This is not just my opinion but is taught to police and is also what most martial artists with knife skills think also. The main thing is to close the distance fast.
You're absolutely correct. Its 21 feet, and is taught in LE academies. This was duscussed over on BF, here's mine and Morimotom's posts (he's a cop in CA)on the topic:
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In response to some other posts, I had posted the following:
Originally Posted by diceman
I forget how many feet it is that the average person with a knife can cover before you can draw your pistol (these are things I should remember right!?) but it something like 15 or 20. A knife is definately not something to be taken lightly, even if you're packing.
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Then Morimotom, who knows what he is talking about, posted this:
also known as the dennis tueller drill, the generally accepted 'rule' is 21 feet.
at that distance the average person can cover 21 feet in 1.5-1.7 seconds, not enough time to draw a gun and fire effectively, generally. even if you know its coming. in other words, if someone is within that distance and decides to charge, you are going to get cut, hit, or tackled before you can react with a firearm.
i try to practice sidestepping and such to counter this type of attack, but i still know a suspect will make physical contact.
i just took another of his classes and asked him again to explain the story, if you get the chance to talk to him, its really fascinating.
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Hope that clears it up a little. Thread is here:
http://www.bladeforums.com/forums/showthread.php?p=4321181#post4321181