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 Massachusetts, Justices of the Peace do not handle the breadth of responsibilities outlined in the description, as the state's judicial system is structured differently than some other states. Massachusetts Justices of the Peace are authorized to officiate weddings, administer oaths, and take acknowledgments, depositions, and protests of negotiable instruments. They do not preside over criminal cases or conduct trials for civil matters. Instead, small claims matters are typically handled by the Small Claims Court, a division of the District Court, while more significant civil and criminal cases are heard in the appropriate trial courts. Traffic violations and other minor criminal offenses are generally handled by the District Court or the Municipal Court. For issues such as mental health commitments, these are typically overseen by the Probate and Family Court or the District Court. The role of a Justice of the Peace in Massachusetts is largely ceremonial and administrative, rather than judicial in the traditional sense.