Justices of the peace are judges who handle both civil and criminal cases, including small claims court, justice court, and administrative hearings. In practical terms, these are lawsuits over debts, evictions, car accidents, unlawful towing, and property.

Their criminal workload involves disposing of all class C criminal misdemeanor complaints, such as traffic citations, issuance of bad check, and others. These cases involve payment, setting contested cases for trial, and pretrial hearings with the county prosecutor.

Other duties include presiding over peace bond hearings, reviewing applications for mental health or chemically dependent commitments, conducting compulsory school attendance trials, and giving warnings to juveniles required by law. They issue warrants for and conduct hearings concerning seizure and disposition of cruelly treated animals. Most justices of the peace perform marriage ceremonies as well.

In Missouri, the role of justices of the peace has largely been replaced by other judicial officers. Missouri does not have justices of the peace in the traditional sense as described. Instead, the state has a system of circuit courts, associate circuit courts, and municipal courts that handle various legal matters. Associate circuit court judges handle civil cases involving small claims (up to $5,000), landlord-tenant disputes, and other civil matters, as well as class C misdemeanors and other criminal infractions. They also preside over preliminary hearings in criminal cases. Municipal judges deal with municipal ordinance violations, which can include traffic citations and other class C misdemeanors. Duties such as presiding over peace bond hearings, mental health commitments, and compulsory school attendance trials fall under the jurisdiction of the circuit or associate circuit courts. While Missouri judges can perform marriage ceremonies, this is not a primary function of their role. It's important to note that the specific procedures and jurisdictional limits can vary by county and court.