It is the duty of the sheriff to serve, execute and return writs or other legal process issued by a lawful authority. The sheriff shall prepare and file an annual inventory statement of county personal property in his or her custody. The sheriff has charge and custody of the jail and its prisoners, except in counties where a county board of corrections exists and has duties over the jail. It is the duty of the sheriff to keep the peace, apprehend criminals and perform other duties as peace officer. The sheriff may appoint deputies but such deputies may not be the county treasurer, clerk, register of deeds or surveyor.