I've read the Missourri state law, so I'm not asking if my knife is legal. The MO knife law is just as ambiguous & vague as you've all seen in your own states.
The problem is this: What if I made every attempt to carry a legal self-defense knife, but an officer has a differing opinion & says "Hand it over (for confiscation), or you'll be charged..."
Without arguing, I could explain my understanding of the law, and he might get upset.
I could show him a Xerox of the law, or a letter from Bernard Levine. He might get upset.
I could say "You can confiscate it, but please put it somewhere safe (evidence locker?) at the station. A lawyer will contact you soon to retrieve it." If he just takes it home can he (the officer) be charged with stealing?
A quality ($150) knife is not something I'd happily part with. Does the state reimburse me for lawyer's fees if I was innocent all along? (I'm afraid I know this answer...)
For simplicity, let's ignore the possibility of obtaining a Concealed Wepons Permit.
This is a great thread and lots of interesting debate. The OP had some specific questions. I am going to give my opinion on each question in turn.
1. I am concerned that the in the fact pattern, the officer is improperly confiscating the knife. Confiscation should include some type of receipt and a procedure of returning the knife. Here, the officer is offering to accept the knife in return for not charging the owner. This is unconstitutional as in taking property without fair compensation. It also may be construed as some type of bribe as in "give me your knife and I won't charge you." If the officer is confiscating the knife for evidence, then he/she must issue some type of ticket.
2. Don't attempt to argue with the officer. If he/she has reached the opinion that it is illegal, you are not going to change his/her mind. If you get charged, the officer will note your attitude (at least they do here in Colorado) and the DA will take that into consideration in any plea bargain.
3. Showing him a photocopy of the law or a letter from Levine, with all due respect, is just stupid. If I were the DA and this went to trial, I would use the letter or photocopy to argue to the jury that you were some kind of knife nut who carries around a dangerous weapon with questionable documentation - a clear indication of your intent to use the knife as a weapon as opposed to a tool. People who use knives as tools do not carry around copies of the law or letters from Levine. As a practical matter, this sort of stuff will raise a big red flag with the cop as well.
3. You are correct the if the officer keeps the knife after confiscating it, he is stealing it. It is also a violation of your constitutional rights and the officer has probably violated his procedures as well. The problem is proof. Unless you have some type of receipt for the confiscated knife, it is his word against yours. If you had a cell phone, you could dial your own voice mail and record the conversation.
4. Ultimately, you have to balance the cost of the knife against the time, expense and risk of being charged. $150.00 is a lot of money. It is probably 10% of what a lawyer would charge (the going rate in Colorado for simple criminal matters is a $1,500.00 flat fee). If you represent yourself, the DA will want you to plead guilty to something, even if it is a lesser charge in a plea bargain as he/she will want to protect the cop. That being the case, you are going to lose the knife anyway.
5. Absent a separate civil trial for malicious prosecution and/or police misconduct and illegal police procedures, there is no way to recover legal fees. What is worse, you would have to pay a lawyer an hourly rate for the separate civil action, with no real chance of recovering those fees. Your court time will not be reimbursed. Do you really want to lose hours and hours of work?
As loath as I am to say it, in your fact pattern by giving up the $150.00 knife in exchange for not being charged, you are actually accepting the officer's offer of a bribe. This is a small bribe amount compared to what it could ultimately cost you. In your fact pattern, the cop seems to know this and is taking advantage of it. I hate to recommend it, but in your fact pattern, the best solution is to give up the knife, buy a new one and you will still be $1,200.00 ahead in legal fees alone.