If I'm justified in using a knife, then I'm justified in using my pistol. As far as planned, practiced use of a knife, I feel the only real justification is a knife carried on the offside to be deployed in a handgun retention struggle. Otherwise, its either to much weapon or not enough. If I pull a knife against an unarmed individual (without being already beat down) then I'm going to jail. If the assailant is armed, a knife is enough weapon. Assailant pulls a knife, and you pull a knife, your both getting cut-a lot, and you're going to the hospital at best. That being said, if I'm somehow in close contact and fighting for my life, I'm going to use anything I can put my hands on. But I'm still not sure If I'd go for my knife before thumbs to the eyeballs, fish hooking him, or biting his ear off. In close quarters that edge can cut anyone, me included.