Cal. Evid. Code § 702 : CALIFORNIA EVIDENCE CODE — WITNESSES — COMPETENCY — Personal knowledge required
(a) Subject to Section
801, the testimony of a witness concerning a particular matter is inadmissible unless he has personal knowledge of the matter. Against the objection of a party, such personal knowledge must be shown before the witness may testify concerning the matter.
(b) A witness' personal knowledge of a matter may be shown by any otherwise admissible evidence, including his own testimony.