California Code, Evidence Code - EVID § 771

(a) Subject to subdivision (c), if a witness, either while testifying or prior thereto, uses a writing to refresh his memory with respect to any matter about which he testifies, such writing must be produced at the hearing at the request of an adverse party and, unless the writing is so produced, the testimony of the witness concerning such matter shall be stricken.

(b) If the writing is produced at the hearing, the adverse party may, if he chooses, inspect the writing, cross-examine the witness concerning it, and introduce in evidence such portion of it as may be pertinent to the testimony of the witness.

(c) Production of the writing is excused, and the testimony of the witness shall not be stricken, if the writing: