Cal. Penal Code - PEN § 893. Section 893.
(a)
A person is competent to act as a grand juror only if he possesses each of the following qualifications:
(1)
He is a citizen of the United States of the age of 18 years or older who shall have been a resident of the state and of the county or city and county for one year immediately before being selected and returned.
(2)
He is in possession of his natural faculties, of ordinary intelligence, of sound judgment, and of fair character.
(3)
He is possessed of sufficient knowledge of the English language.
(b)
A person is not competent to act as a grand juror if any of the following apply:
(1)
The person is serving as a trial juror in any court of this state.
(2)
The person has been discharged as a grand juror in any court of this state within one year.
(3)
The person has been convicted of malfeasance in office or any felony or other high crime.
(4)
The person is serving as an elected public officer.