Age limits

In Australia, young people may be charged with a criminal offence if they are aged 10 or over. Separate justice systems operate for young people and adults, each with specific legislation. The upper age limit in the youth justice system is 17 (at the time of the offence) in most states and territories. Those aged 18 or over are dealt with under the adult justice system.

In 2020–21, 1 in 4 young people under supervision on an average day were aged 18 or over (AIHW 2023). Reasons for this include:

  • Young people may be apprehended for an offence that was committed or allegedly committed when they were aged 17 or younger.
  • Young people may continue to be supervised by the youth justice system once they turn 18 (or they may be transferred to the adult correctional system).
  • Some young people aged 18 or over are supervised by youth justice agencies due to their vulnerability or immaturity (in some jurisdictions).
  • Young people aged between 18 and 20 in Victoria who appear in courts other than the Children’s Court may be sentenced to detention in a youth facility rather than an adult prison if assessed as suitable and the court deems this appropriate. This is known as the ‘dual track’ sentencing system.

In this report, the term ‘young people’ has been used to refer to individuals aged 10 and over who are supervised by a youth justice agency. Numbers of young people in detention relate to young people of all ages unless otherwise specified.

Population rates allow for the comparison of different groups while taking into account different population sizes. In this report, rates have been calculated only for young people aged 10–13, 14–17 and 10–17, as these are the key populations in most states and territories. For more information about the calculation of rates see Technical notes.

For this report, the age on an average night each quarter has been calculated based on the age a young person is each night that they are in detention. If a young person changes age during a period of detention, then the average nightly number in detention will reflect this.

Average nightly data broken down by age will not be comparable to Youth detention population in Australia releases prior to 2020. For more information about the calculation of age, see Technical notes.