Mo. Rev. Stat. § 302.440: Devices, use of, when.

In addition to any other provisions of law, a court may require that any person who is found guilty of a first intoxication-related traffic offense, as defined in section 577.001, and a court shall require that any person who is found guilty of a second or subsequent intoxication-related traffic offense, as defined in section 577.001, or any person who is found guilty of an intoxication-related traffic offense, as defined under section 577.001, in which the person's blood alcohol content was found to be fifteen-hundredths of one percent or more by weight of alcohol in such person's blood, or in which the person caused any property damage or personal injury shall not operate any motor vehicle unless that vehicle is equipped with a functioning, certified ignition interlock device that the person must use for a period of not less than six months from the date of reinstatement of the person's driver's license. In addition, any court authorized to grant a limited driving privilege under section 302.309 to any person who is found guilty of a second or subsequent intoxication-related traffic offense or to any person who is found guilty of an intoxication-related traffic offense, as defined under section 577.001, in which the person's blood alcohol content was found to be fifteen-hundredths of one percent or more by weight of alcohol in such person's blood, or in which the person caused any property damage or personal injury shall require the use of an ignition interlock device on all vehicles operated by the person as a required condition of the limited driving privilege, except as provided in section 302.441. These requirements shall be in addition to any other provisions of this chapter or chapter 577 requiring installation and maintenance of an ignition interlock device. Any person required to use an ignition interlock device shall comply with such requirement subject to the penalties provided by section 577.599.