You should talk to an attorney that is truly knowledgeable in the area. To contradict many of the other posts, indeed there are valid arguments that may exist in your case even if your case is pre-McNeely. It may be tough but those that say there is not an argument, in my opinion are not sufficiently up on all of the law in this area. There are some very good lawyers in the Madison are that know what the law is and you may wish to talk to them. they are expensive but may be worth it for your...
The short answer to your question is that the judge will have to decide. The judge will have to evaluate all of the information presented at any hearing to challenge the case. You may indeed have a defense. You should consult with an attorney in your area as soon as you can to discuss the matter. The answer to your question will likely be quite detailed and specific to the facts of your case. You need a lawyer. Good luck.
This sounds like it is a non criminal citation. Likely there will not be a greater penalty if you pay versus going to court and losing. Bit if you go to court and win then there is not any penalty. Also, note that the merchant can pursue civil action too. That may be incentive too to fight the ticket. Good luck.
Assuming that the facts are as you say, and given that this is in Eau Claire it appears, my experience in this county tells me that there are several favorable options available to help your son with this case. He should contact an attorney and he should stop making statements against himself. Good luck.
You can go online and Google the elements of the offense for the crime. Also you can look at the legal guide I put out a few days ago on 9-5 re: a basic overview of "conspiracy". You need to get a lawyer. I think you are the person that has asked a lot of questions on this forum already and it seems that you are trying to handle on your own something that you should get help with. Don't be foolish. Get a lawyer.