Mo. Rev. Stat. § 550.290

In order to make said sections 550.260 to 550.300 effective, it is hereby declared that all fees due by the state or county on account of any criminal case, or due witnesses before the grand jury, or as a juror or witness in an inquest, shall not be negotiable or assignable except subject to all the setoffs herein provided for, and that the state and county holds a prior lien on the same for the purpose of indemnification against loss by reason of the nonpayment of personal back taxes, and for the payment of the fines, penalties, forfeitures and costs herein mentioned.