• that the custody and supervision system helps to keep the family and members of the public involved with youth;
• that the custody and supervision decisions be straightforward, fair and timely;
• that youth have access to an effective review procedure;
• that when youth are placed where they are treated as adults, this does not disadvantage them when it comes to their eligibility for, and conditions of, release (section 83(2)).

Custody is only to be used for violent offenders and serious repeat offenders. To help make sure that custody is only used when absolutely necessary the Youth Criminal Justice Act includes restrictions defining when it can be used. A young person cannot be given custody unless:

• he or she has committed a violent offence;
• he or she has failed to comply with non-custodial sentences;
• he or she has committed an indictable offence and has a history that shows a pattern of findings of guilt, or;
• it is an unusual or exceptional case where he or she has committed an indictable offence and it would be impossible to give a sentence other than custody that would be consistent with the purpose and principles of sentencing (section 39).

Before the youth can receive a custody and supervision sentence, the court has to consider all of the other community based sentences that would be reasonable for the case and circumstances. When trying to decide if there is a reasonable choice other than custody, the judge has to look at what other sentences are available, how likely it is that the youth will comply with the community based sentence and other sentences that have been given in similar cases.

Youth must be kept in custody separately from adults. This may mean in a facility entirely for youth or it may mean that a local remand centre has a distinct unit for youth only.

The Youth Criminal Justice Act distinguishes two levels of custody that reflect the degree of restraint imposed on the young person (section 85(1)). The two levels of custody allow for greater flexibility when sentencing a youth to custody. When determining the level of custody for the young person several factors are to be considered:

• the level of custody that is least restrictive having considered the seriousness and circumstances of the offence, the needs and circumstances of the young person, the safety of other young persons in custody, and the interests of society,
• the level of custody that will allow for the best possible programs available for the young persons needs and behavior,
• the likelihood of escape (section 85(5)).