Grand Juries have existed in California since the original constitution of 1849-50.  There was a gradual evolution of the process during the following 30 years that defined its basic concepts and authority.  Although certain aspects have been refined over the years, they all derive from those original principles.  

The codification of Grand Jury law came about in 1872 with the adoption of the Penal Code and that is where most Grand Jury law resides.  This code included inquiring into local prisons, auditing of county books, and examining matters of "community interest."  Finally, in 1880, the grand jury was authorized to investigate local governments.