Justices of the Peace have original jurisdiction in criminal cases punishable by fine only, or punishable by a fine and a sanction not consisting of confinement or imprisonment. Criminal procedures for cases that are within the criminal jurisdiction of the Smith County Justice Courts are found in Chapter 45 of the Texas Code of Criminal Procedure. The Rules of Evidence governing the trials of criminal actions in the District Courts apply to a criminal proceeding in the Justice Courts. The Smith County District Attorney prosecutes traffic cases filed in the Smith County Justice Courts.

In addition to class "C" traffic offenses, the Justice of the Peace Court also handles a variety of criminal class "C" misdemeanors. Some of the more common offenses besides traffic, hot checks, and truancy include disorderly conduct, assault, public intoxication, minor in possession of alcoholic beverage, and shoplifting. In cases involving alcohol violations, an alcohol awareness course is usually required.