[eka]

"Knife armed felon. You only become a felon when you have been convicted of the offence- not when you perpetrate it."

That is correct, one is presumed innocent until convicted in court. However, in this context, I think the intention was to convey that this was a violent felony suspect.

"once you see the guy coming at you with a knife in his hand, shoot him immediately before he has the chance to drop the knife and give up so the immediate threat is always there"

Now don't you think that is going a little beyond the scope of self-defense. That would be the work of an individual looking for an excuse to shoot someone. If there is a legitimate and immediate threat, you have the right to do whatever you can do to stop the threatening behavior. If it's not there, it's not there period. Otherwise, you become an assailant armed with a deadly weapon, just like the bad guy. However, I know we are just discussing hypotheticals here.