The sentence to be imposed is generally fixed by statute. In some cases (mandatory sentencing) the duration is exactly prescribed; in others the judge (and in some instances, the jury) has limited discretion. The U.S. Supreme Court has held that courts in sentencing may, and sometimes must, consider not only the crimes for which a defendant was convicted, but also other charges, even if they led to acquittal. The Court has also ruled that only a jury may make the factual findings that can increase a sentence beyond the usual range specified in law for a crime. If a person is convicted of more than one crime at a single trial, the sentences may run concurrently (i.e., all beginning at the same time) or consecutively. In indeterminate sentencing, a minimum and maximum term is set, and good behavior may allow a convict to be released on parole any time after the minimum term has been served. In many states successive convictions on felony charges bring longer sentences, and in the 1980s some U.S. states and the federal government began to impose "three strikes" and similar laws, ordering mandatory long-term or life imprisonment for repeated felony offenses. Such laws have been criticized for sometimes requiring long sentences for nonviolent offenders whose crimes may include petty theft or drug possession. Persons found incapable of understanding the nature of their crimes or of helping in their defense are often committed to mental institutions for periods that are to end if they recover sanity; these are effectively, if not technically, sentences. See also verdict, jury, and pardon.