Sentencing of the criminal offender is the central activity of the criminal justice system. The majority of cases prosecuted in criminal courts result in a determination of the defendant's guilt. Whether prosecution leads to a formal trial or to a negotiated plea, the sentence is the culmination of the judicial process. There are two basic problems in present sentencing practices. The first results from the contradictions inherent in a criminal system whose purposes include both punishment and rehabilitation. Punishment is believed to further the goals of deterrence, retribution and protection. It requires that an offender be denied access to opportunities and resources readily available to non-criminals. Rehabilitation, on the other hand, is intended to produce inmates who are ready to assume responsible roles in the community after release. It requires that an offender receive guidance, supervision and training in excess of that freely available to the average citizen. Thus, it is not surprising that judges often find it impossible to impose punishment and to prescribe rehabilitory measures at the same time. They must choose one at the expense of the other or strike a compromise which serves neither goal satisfactorily. The second problem of sentencing lies in its future-oriented nature. A sentence tries to predict how an offender will behave under certain circumstances and how other potential offenders will behave. 1 The task of predicting the outcome of judicial dispositions is complicated by several factors. For example, although judges have considerable latitude in deciding the fate of convicted offenders, few have sufficient knowledge of behavioral laws (which are frequently at odds with conventional wisdom) to make socially optimal choices. Also, the failure of correctional officials to systematically evaluate various correctional programs has resulted in a paucity of descriptive data regarding the manner in which different individuals will respond to different rehabilitation efforts.2 Moreover, judges seldom observe and are not held accountable for the impact which a sentence has on the subsequent behavior of an offender. Consequently, they are not strongly motivated to improve their performance. The net effect of these influences is haphazard sentencing practices that are rarely standardized even within a single jurisdiction.