Because of our system of government that distributes power among national, state, and local levels, the location in which a person is arrested determines the departments that will deal with his/her case. If you're not familiar with the legal field, this can cause a great deal of confusion, and even some problems if you fail to communicate with the proper agencies. Seek the help of a qualified and experienced criminal defense attorney to help you determine the right course of action.
When you confer with a defense lawyer, one of the first things he/she will need to know is the county in which the arrest took place, since each county has its own superior court that handles violations of the law - infractions, misdemeanors, and felonies. If the arrest takes place in Yolo County, the case will be heard at the courthouse in Woodland. If the arrest takes place in Placer County, in most instances it will be heard at the courthouse in Roseville. Most cases in Sacramento are dealt with at the main courthouse in downtown Sacramento. Some, however, are heard in courtrooms at the county jail, and traffic cases are heard at the Carol Miller Justice Center. Juvenile cases in all counties are usually heard in facilities separate from those used for adults.
Each county also has its own district attorney's office, which prosecutes criminal cases, and sheriff's department, which staffs the county jail and patrols unincorporated areas or smaller cities that have decided to contract with the sheriff for law enforcement services.
If a city maintains its own police force, people who are arrested are taken to the local county jail. Thus, the City of Elk Grove police take people to the Sacramento County jail, while the City of Rocklin police take people to the Placer County jail.
That's not quite the whole story, though. To complicate matters, there is the California Highway Patrol, which focuses its efforts on freeways and major roads throughout the state. CHP personnel can be involved in arrests throughout the Sacramento region. But they will still take people to the local county jail.
To give a practical example, the DUI checkpoints that you might encounter this holiday season can be run by any of the law enforcement agencies listed above, and perhaps even a combination. If a person is found to be under the influence, he/she will be arrested and taken to the jail in that particular county..