In most states persons accused of violating the law before they are 18 years of age are under the jurisdiction of the juvenile courts, and persons accused of violating the law when they are 18 years of age or older are under the jurisdiction of the criminal courts. Some states begin prosecuting persons as adults in the criminal court system when they are 17 years of age, and some states begin prosecuting persons as adults in the criminal court system when they are 16 years of age.

But all states have transfer laws that permit or require criminal prosecution of some young offenders—even though they are still of juvenile age, as defined by the state’s laws. Transfer laws vary from state to state, but generally fall within three categories: (1) judicial waiver laws that allow juvenile courts to waive jurisdiction on a case-by-case basis; (2) prosecutorial discretion or concurrent jurisdiction laws that define a class of cases that may be brought in juvenile court or in criminal court—usually at the discretion of the prosecutor; and (3) statutory exclusion laws that grant criminal courts exclusive jurisdiction over certain classes of cases involving juvenile-age offenders.

The laws that govern when a person of juvenile age may be prosecuted as an adult in the criminal court system are generally located in a state’s statutes.

In Montana (MT), the jurisdiction of juvenile courts typically covers individuals who are accused of violating the law before they reach 18 years of age. Those who are 18 or older are prosecuted in the criminal courts. However, Montana, like other states, has transfer laws that allow for certain juvenile offenders to be tried as adults in the criminal court system. These transfer laws include judicial waiver laws, where juvenile courts have the authority to waive their jurisdiction and transfer a juvenile case to criminal court. Prosecutorial discretion or concurrent jurisdiction laws also exist, where prosecutors can decide whether to file charges in juvenile or criminal court for certain offenses. Additionally, statutory exclusion laws in Montana may automatically exclude certain serious offenses from juvenile court jurisdiction, requiring that those cases be tried in the criminal court system. The specific provisions and criteria for transferring juvenile cases to adult court are detailed in Montana's state statutes.