After a defendant is convicted of a crime, he or she may be sentenced to prison. When that occurs, the defendant will usually be held in the county jail until he or she can be taken into the custody of the state's prison system. U.S. prison populations include many "hardened criminals" who have been convicted of a significant crime or series of crimes, while a county jail might contain many people who have not yet been convicted and are thus presumed innocent, first-time offenders, who do not have a severe criminal mindset, along with more serious offenders who have not yet been convincted or sentenced, or are awaiting transfer to prison.