Indeterminate sentencing essentially views the offender as a patient who is not released from the 'hospital' until those in charge perceive that he/she is 'well'. The medical model for treating offenders, however, is far from being as scientifically precise as biological medical practice. Judgments about 'wellness' tend to be arbitrary and subjective, leaving some offenders in prison for long periods while others convicted of the same offense serve much shorter prison terms. Determinate sentencing, on the other hand, ensures that persons convicted of similar crimes will serve similar sentences prescribed according to the severity of the offense. The decision about release is made by the judge and cannot be revised by correctional or parole authorities. In Illinois, however, the offender may reduce the prescribed sentence 1 day for each law abiding day in prison. Under such a system, a parole board is unnecessary. Under determinate sentencing, rehabilitation programs are not discarded but are made voluntary and independent of time served, except as they may contribute indirectly to behavior that will establish 'good time' credits.