I agree with Hugh also. There is a very thin window in most of the 50 states were the use of deadly force is justified. And as Hugh mentioned even if the use of forced ends up being justified , in todays legal "enviorment" , you'll much more likely than not have to face civil charges of one sort or another. I don't see a problem with carrying a knife of some sort clipped in a pocket..front , back whatever , but if your gonna pack your knife there are a couple things to keep in mind.. one , be sure it's legal. and two , if you carry with self defense in mind..I believe you are then obligated to get some basic training in the use of that weapon and to stay current. If you don't your only endangering yourself and others around you.
In todays world , a knife , especially the folder that most of us carry is certainly not the weapon of choice for realistic self defense and you can bet it's not the weapon that you'll most likely face in a conflict.
I don't mean to preach..and the details are'nt important..but I've "been down this road" and I'm just being honest. The one other thing I'll say is , if your gonna carry any weapon.. knife , firearm or whatever..as a means of self defense...think very carefully about your decision and be sure that's what you really wanna do. Once you've made that decision you must be totally committed and ready to use that weapon.. showin' off don't cut it. That's another real good way to get yourself or someone around you hurt or killed. Ok , I'll get down off my soapbox.