A juvenile offender is an offender who is too young to be tried as an adult. The age at which a person can be tried as an adult varies between states, but is ordinarily the age of seventeen or eighteen. This age can go down for certain serious offenses, such as homicide or sexual assault.
When a juvenile is charged with a criminal offense and is sent to a juvenile court, the focus is ordinarily on what will rehabilitate the juvenile, rather than on punishment. Often, the offender will be said to have committed a delinquent act, as opposed to a criminal offense, with the court's finding of guilt or responsibility being deemed a disposition or adjudication, as opposed to a conviction.
A juvenile court has broad discretion to tailor a sentence to the needs of a young offender. This is not to say that juveniles are not sentenced to prision -- many states have large juvenile prisons and treatment facilities. It is understood that some juvenile offenders are very dangerous, despite their age, and that incarceration can be appropriate.
The specific rights afforded to a juvenile offender vary significantly from state to state. In some states, juveniles have the right to trial by jury, while in others they have no such right. Juvenile courts tend to be less formal than adult courts. Sometimes, the rules of evidence will be more relaxed, and evidence will be heard to judge the juvenile's "delinquency" which would not be allowed at an adult's criminal trial.
A juvenile offender who has committed a serious offense may be waived from juvenile court to adult court. Sometimes this is a discretionary waiver, where the prosecutor files a motion to have the young offender tried as an adult. After a hearing, where evidence is presented for and against a waiver, the judge decides whether the offender should be tried as a juvenile or an adult. Sometimes, this is a mandatory waiver, where the law requires the young offender to be tried as an adult. Many states have passed laws allowing prosecutors to file adult charges against juveniles for certain serious offenses, without having to apply for a waiver.
A juvenile tried in adult court receives all of the rights granted to an adult defendant, including the right to a jury.
The answer to this question varies from state to state, and sometimes from charge to charge. Some states grant a judge the discretion to sentence a juvenile offender as a juvenile, even though he was tried as an adult. Some states mix the sentence, imposing both a juvenile and an adult sentence. In such states, the adult sentence is only imposed if the juvenile violates the terms of his juvenile sentence. Sometimes, the Court will sentence the juvenile as an adult -- a result that can be very harsh in murder cases, where the juvenile may be sentenced to life in prison without the possibility of parole.
The availability of a juvenile record depends upon state law, and can vary significantly depending upon such factors as subsequent criminal activity or the type of crime committed. If a juvenile is convicted of certain sex offenses, he may be required to register as a sex offender as an adult, regardless of his age at the time of conviction. In some states which automatically seal a juvenile's record once he passes a certain age, that record may remain unsealed if the defendant is convicted of an adult offense before he reaches that age. In some states, a person must petition a court to seal a juvenile record shortly after reaching the age of majority, or the record will remain public.