Under the one-third rule, which was dropped three decades ago, judges must issue minimum prison sentences for criminal offenses that are no longer than one-third of the maximum sentence. Under the rule, someone sentenced for a crime that carried a 50-year maximum sentence would get a minimum sentence of no more than 162⁄3 years. The minimum sentence determines when an inmate is eligible for release on parole, so a shorter minimum sentence results in a quicker release from prison, according to prosecutors. Read More.