Mandatory sentencing requires that people convicted of certain crimes serve a predefined term of imprisonment, removing the discretion of judges to take issues such as extenuating circumstances and a person's likelihood of rehabilitation into consideration when sentencing. Research shows the discretion of sentencing is effectively shifted to prosecutors, as they decide what charges to bring against a defendant. Mandatory sentencing laws vary across nations; civil law jurisdictions usually prescribe minimum and maximum sentences for every type of crime in explicit laws. They can be applied to crimes ranging from minor offences to extremely violent crimes including murder. In the United States, several mandatory sentencing laws have been overturned by the Supreme Court for being unconstitutional, and mandatory sentencing has resulted in prison terms that are considered extremely disproportionate compared to the crimes committed.