California Code, Evidence Code - EVID § 751

(a) An interpreter shall take an oath that he or she will make a true interpretation to the witness in a language that the witness understands and that he or she will make a true interpretation of the witness' answers to questions to counsel, court, or jury, in the English language, with his or her best skill and judgment.

(b) In any proceeding in which a deaf or hard-of-hearing person is testifying under oath, the interpreter certified pursuant to subdivision (f) of Section 754 shall advise the court whenever he or she is unable to comply with his or her oath taken pursuant to subdivision (a).

(c) A translator shall take an oath that he or she will make a true translation in the English language of any writing he or she is to decipher or translate.

(d) An interpreter regularly employed by the court and certified or registered in accordance with Article 4 (commencing with Section 68560) of Chapter 2 of Title 8 of the Government Code, or a translator regularly employed by the court, may file an oath as prescribed by this section with the clerk of the court. The filed oath shall serve for all subsequent court proceedings until the appointment is revoked by the court.