Other chapters in the present volume explore sentencing factors in jurisdictions such as South Africa, Canada or New Zealand, where courts impose sentence in the absence of formal guidelines. Across the United States, however, many jurisdictions employ formal sentencing guidelines, often in the form of a two-dimensional sentencing grid. These guidelines establish a ‘presumptive’ range of sentence for all offences. One of the most well-known and often studied systems is found at the federal level and applies to all offenders sentenced in the federal courts. The US Sentencing Commission issues these guidelines. The federal guidelines employ a two-dimensional grid (offence seriousness; criminal history) with 256 cells that delineates six-month sentencing ranges.

Since their adoption in 1987, the US federal sentencing guidelines have required the use of narrow mandatory sentencing ranges in almost every case, thereby contributing to the creation of one of the largest prison populations in the world (Luna 2005; Stuntz 2001). In determining ranges the mandatory sentencing guidelines identified which aggravating factors must be considered while severely restricting the consideration of mitigating factors at sentencing, disfavouring most potential mitigating factors (Tonry 1996).