A chart aimed at standardizing the amount of time served as a result of federal criminal cases. Down the lefthand side are severity levels. Across the top are columns for criminal history. In the middle are sentence ranges, in months.

Every crime in the federal criminal code is designated with a severity level by the Federal Sentencing Commission. After conviction, the severity levels of all charges (even those that resulted in an acquittal) in a case are added up. The judge looks at the chart, selects the appropriate criminal history (one for a first time offender, two for a second offence, etc), chooses the sentence range appropriate to the severity level. The range of the judge's discretion is anywhere from 6 months (for sentences less than 24 months) to over 12 months (sentences over 60 months).

Lawyers for the defense and prosecution can submit motions for upward or downward departures from the guidelines, but variations are rare.

The overall effect of these guidelines is to emasculate federal judges in criminal cases, and put the power of sentencing in the hands of politically-appointed US Attorneys. Rather than the traditional idea of plea bargaining, federal criminal negotiation is about charge bargaining, a process of determining which of the miriad charges relevant to any crime will be applied to a particular case.

Source: my attorney, personal experience