I was unaware that due process is no longer existent. Good to know.
Well, this particularly letter is almost certainly not part of the required due process. As I understand the context of your statement, the due process you are referring to would apply to the method by which you are made aware of the criminal court proceeding. You are correct that the court would still have to serve the warrant or summons, and there are clear rules about how that must be served. http://www.supremecourt.ohio.gov/LegalResources/Rules/criminal/CriminalProcedure.pdf But that is irrelevant to this first class letter demanding payment. This is merely an attempt to collect without having to file formal charges. If you ignore the letter, they just move to the next phase of their collection procedure. But getting you to respond to the letter, or even proving you received it, is completely irrelevant to the issue of whether you committed the underlying criminal offense, and whether they can proceed to prosecute you.