LATEST: Nicole Richie is a free woman after serving just over an hour of a four-day sentence in prison. The pregnant socialite was booked, released and sent home in an 80-minute spell at the Century Regional Facility in Lynwood, California on Thursday (23Aug07). A spokesman for the Los Angeles County Sheriff's Department explains prison population levels prompted officials to release Richie after the briefest prison spell. In a press release, the sheriff's spokesman writes, "At thistime, the criteria for a female arrestee sentenced to 30-days or less for a non-violent offense is as follows: the arrestee is booked, screened and usually released within 12 hours. "This procedure is based on jail overcrowding to manage population levels mandated by Federal Court guidelines. Based on the mandated guidelines and Ms. Richie's 96 hours sentence, she will be treated in the same manner as other inmates with a similar sentence." Richie was charged with a misdemeanor DUI on 27 July (07) and was sentenced to 36 months of summary probation. If she violates probation, she will have to serve one year in jail. Richie was arrested on 11 Deceember (06) when she found driving her Mercedes Benz the wrong way down California State Route 134 highway in Burbank, California. After failing an on-field sobriety test, Richie admitted to having smoked marijuana and taking a vicodin painkiller. Richie is five months pregnant with rocker boyfriend Joel Madden's baby.