After an offender has been convicted, the process of imprisonment begins at the time that the court orders the term of imprisonment. From that point on and for the remainder of the sentence the prisoner is legally in the custody of the Chief Executive Officer of the Department of Correctional Services [Correctional Services Act 1982 s.24].

In most cases, time already spent in gaol awaiting trial or sentence is taken into account when the sentence is finally imposed, or the sentence may be 'back dated' to the date the person was taken into custody.