Cal. PEN § 903.2

The jury commissioner shall diligently inquire and inform himself or herself in respect to the qualifications of persons resident in his or her county who may be liable to be summoned for grand jury duty. He or she may require a person to answer, under oath to be administered by him or her, all questions as he or she may address to that person, touching his or her name, age, residence, occupation, and qualifications as a grand juror, and also all questions as to similar matters concerning other persons of whose qualifications for grand jury duty he or she has knowledge.

The commissioner and his or her assistants, referred to in Sections 69895 and 69896 of the Government Code, shall have the power to administer oaths and shall be allowed actual traveling expenses incurred in the performance of their duties. Those traveling expenses shall be audited, allowed, and paid out of the general fund of the county.