I have met makers who expressly made and designed their knives in such a way as to avoid ever having one of them being used as a weapon.
Not exactly what I would call a 100% foolproof method, but the effort to that effect helped him sleep at night.
There really is no cut and dried right and wrong answer to this sort of question. It really boils down to your opinion of the secondary enabler position, and its importance in the commission of a crime.
For example, as many have already pointed out, the weapon does not do the killing, but rather the person using the weapon does the killing.
On the other hand, somebody made that weapon, be it a firearm or a knife.
Flip side to that of course, is that the person who made the weapon created nothing more than a replaceable tool, and the violent miscreant who misused that tool would have done the same with a different tool had that one not been available.
and then, of course, the response to that is the obvious intent of the design. For example, a shiv like is under discussion is quite obviously a people cutting knife. It was not made to cut boxes, clean fish, skin game, or whittle a block of wood. It would be akward at any of those tasks when compared to a knife properly made to the task in question.
And, again, yet another response to that.
So on and so on and so on and so on... Ad infinitum!
Fact of the matter is, you really need to answer two basic questions:
1: do you choose to blame the one with blood on his hands for his actions, or the one who created the scary looking tool he happened to have?
2: do you believe that in designing a weapon that is quite obviously a weapon with no other legitimate purpose you are influencing people to use that weapon in an illegal, irresponsable, or unethical manner?
I, personally choose to blame the guilty. I choose to blame myself for making knives. It is something I like doing, that can be mildly profitable from time to time. Of the crime of bladesmithing, I am guilty as charged.
I also blame violent crime on violent criminals. For one reason or another, a given individual displays a lack of sufficient self control, discipline, or concern. Be it a temporary or chronic flaw, the flaw is not to be blamed on me just because it was a knife I made in his hands when he went wrong. It could have just as easily been a bat, a gun, a pen, a letter opener, etc. If I hadn't made the knife, he still would have screwed up.
As for the second question, no. Knives do not make you go cut someone anymore than guns make you go shoot someone. So it looks scary to some, so freaking what? Did violent crime drop one iota due to the so called assault weapon ban our good friend billy force fed us a few years back? Although all of the really scary looking guns were supposed to be out of reach, people got shot anyway.
Finally, you can rest pretty well knowing that if you charge a hundred dollars or more, the chances are your knife won't be used in a criminal act. That is NOTto say that noone with even that modest means could be a violent criminal. Far from it. It is, however, very easy to find knives for under a hundred bucks. They are common. They are everywhere. Sombody has to WANT a really good knife to pay $100.00 or more for a single knife. The folks who want a well made knife that bad aren't about to pony up the required cash just to go get it taken by the fuzz when they step out of line with their new purchase!
) Is it responsible of me to bring these things to the (black) market, knowing that in our peaceful society nobody has human-destroying tools? There was a stabbing recently in my home town, and the knife broke during the stabbing. Good thing that wasn't a good assault knife! On the other hand, weapons may be an important part of being human and thinning the herd? I'll think about it more carefully, especially if I ever progress to uncommon weapons that have the power to kill many humans in a short amount of time...
