Cal. Penal Code § 939.21

(a) Any prosecution witness before the grand jury in a proceeding involving a violation of Section 243.4, 261, 273a, 273d, 285, 286, 287, 288, 288.5, or 289, subdivision (1) of Section 314, Section 368, 647.6, or former Section 288a or 647a, who is a minor or a dependent person, may, at the discretion of the prosecution, select a person of his or her own choice to attend the testimony of the prosecution witness for the purpose of providing support. The person chosen shall not be a witness in the same proceeding, or a person described in Section 1070 of the Evidence Code. (b) The grand jury foreperson shall inform any person permitted to attend the grand jury proceedings pursuant to this section that grand jury proceedings are confidential and may not be discussed with anyone not in attendance at the proceedings. The foreperson also shall admonish that person not to prompt, sway, or influence the witness in any way. Nothing in this section shall preclude the presiding judge from exercising his or her discretion to remove a person from the grand jury proceeding whom the judge believes is prompting, swaying, or influencing the witness.