Western criminal justice systems have varied in their approach to crime, but the concept of treating offenders who are not yet adults differently is a relatively recent development. Juvenile offenders—that is, participants of illegal behavior—are typically individuals under the age of 18. In 10 U.S. states, a minor is no longer considered a juvenile offender at the age of 17; and in Connecticut, North Carolina, and New York, juvenile jurisdiction expires at the age of 16. Once a juvenile is judged a delinquent in court, he or she may be confined or monitored until the age of 24, depending on the state.

The minimum age to be tried as a juvenile offender also varies between state legislatures. Although most states do not have a minimum age, ...