Mo. Rev. Stat. § 578.437
No weapon shall be declared a nuisance pursuant to section 578.435 and this section unless reasonable notice has been given to the lawful owner thereof, if his or her identity and address can be reasonably ascertained. The law enforcement agency shall inform the lawful owner at that person's last known address by registered mail that the owner of the weapon has thirty days from the date of receipt of the notice to respond to the clerk of the court to confirm his or her desire for a hearing, and that the failure to respond shall result in a default order and thereupon such weapon shall be declared a nuisance. If the person requests a hearing the court shall set a hearing no later than sixty days from the receipt of such request, and shall notify the person, the law enforcement agency involved, and the prosecuting attorney of the date, time, and place of the hearing. At such hearing the burden of proof shall be upon the state to show by a preponderance of the evidence that the seized item has been or will be used in criminal street gang activity, or that the return of the weapon would likely result in the endangering of the lives of others.
§ 578.437, RSMo