The central innovation of the guidelines sentencing revolution has been the creation of a regime in which facts other than those required for conviction have necessary consequences at sentencing. In days of yore, judges mulling a sentence were entitled to receive information from virtually any source on virtually any subject, but they were never obliged to pass public judgment on the truth or falsity of what they heard because no finding of fact could constrain their discretion to set a sentence anywhere within the boundaries set by statutory maxima and minima. No more. The project of the original United States Sentencing Commission was to identify those facts that ought to influence sentencing outcomes and then to create a set of rules embodying the command that sentences would be affected whenever the identified facts were found. The idea was to bring law to a region of the criminal justice system thought to be lawless by making sentencing a more adjudicatory and less discretionary process.
Frank O. Bowman III, Completing the Sentencing Revolution: Reconsidering Sentencing Procedure in the Guidelines Era, 12 Fed. Sent. R. 187 (2000)