Mo. Rev. Stat. § 137.150
Assessors and deputy assessors, county and circuit clerks, notaries public, commissioners of the county commissions, associate circuit judges, and all other judicial officers, are empowered and authorized to administer any oath relating to the assessment of property required by this chapter, and the assessor shall be liable to a fine of not less than ten dollars, to be recovered by suit or by indictment, for each list he shall receive without the same has been duly sworn to before some such officer; provided, he shall not be subject to a fine in any case where he or his deputy has made out the same on his own knowledge or information, in the absence of the person whose property is listed, or where he or his deputy has made it out on the refusal of the taxpayer to make it out and to swear to it; and it shall be the duty of the court having jurisdiction in criminal cases to give this section in charge of the grand jury at each term of the court.
§ 137.150, RSMo