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 Missouri, the general rule is that individuals are considered juveniles for the purposes of the legal system until they reach the age of 18. However, Missouri does have provisions that allow for the prosecution of juveniles as adults under certain circumstances. These provisions include judicial waiver laws, where a juvenile court judge can decide to transfer a case to adult criminal court; prosecutorial discretion laws, which give prosecutors the authority to file charges in either juvenile or adult court for certain offenses; and statutory exclusion laws, where the state statutes automatically exclude certain serious offenses from juvenile court jurisdiction, meaning those cases go directly to adult court. The specific criteria and procedures for transferring a juvenile case to adult court are detailed in Missouri's state statutes, and the decision to prosecute a juvenile as an adult takes into account factors such as the age of the offender, the seriousness of the offense, and the juvenile's prior record.