Spouse’s testimony before a grand jury does not waive a subsequent claim of the spousal testimonial privilege at criminal trial. Petrill drove a stolen van around San Francisco one night, transporting his wife and two acquaintances to various locations where the acquaintances committed robberies. After the fourth robbery, police spotted the van and attempted to stop it. A high speed chase resulted in a collision that killed an officer. At trial, Petrill’s wife testified against him over a defense objection under the spousal testimonial privilege. (Evid. Code, §§ 970, 971.) The trial court found that the wife waived the privilege by testifying under subpoena before a grand jury. Petrill was convicted of felony murder with special circumstances, four counts of robbery, and other crimes. On appeal he challenged admission of his wife’s testimony. Held: Reversed in part. Waiver of the spousal testimonial privilege is governed by Evidence Code section 973, which provides that “a married person who testifies in a proceeding to which his spouse is a party, or who testifies against his spouse in any proceeding, does not have a privilege . . . in the proceeding in which such testimony is given.” The grand jury is an investigative body, which, if it finds probable cause to believe a crime has been committed, prepares an indictment. A grand jury proceeding is not adversarial and an indicted person is not deemed to have been a “party” to the proceedings. Additionally, a criminal prosecution is a different “proceeding” from grand jury proceedings and any waiver resulting from grand jury testimony does not carry over to a criminal trial. The grand jury’s limited role in the charging process distinguishes it from a subsequent criminal proceeding, which does not even exist before the indictment is filed. The error in allowing Petrill’s wife’s testimony was prejudicial in connection with three of the robberies.