2009 California Evidence Code - Section 720-723 :: Article 1. Expert Witnesses Generally

720.  (a) A person is qualified to testify as an expert if he has
special knowledge, skill, experience, training, or education
sufficient to qualify him as an expert on the subject to which his
testimony relates. Against the objection of a party, such special
knowledge, skill, experience, training, or education must be shown
before the witness may testify as an expert.
   (b) A witness' special knowledge, skill, experience, training, or
education may be shown by any otherwise admissible evidence,
including his own testimony.

721.  (a) Subject to subdivision (b), a witness testifying as an
expert may be cross-examined to the same extent as any other witness
and, in addition, may be fully cross-examined as to (1) his or her
qualifications, (2) the subject to which his or her expert testimony
relates, and (3) the matter upon which his or her opinion is based
and the reasons for his or her opinion.
   (b) If a witness testifying as an expert testifies in the form of
an opinion, he or she may not be cross-examined in regard to the
content or tenor of any scientific, technical, or professional text,
treatise, journal, or similar publication unless any of the following
occurs:
   (1) The witness referred to, considered, or relied upon such
publication in arriving at or forming his or her opinion.
   (2) The publication has been admitted in evidence.
   (3) The publication has been established as a reliable authority
by the testimony or admission of the witness or by other expert
testimony or by judicial notice.
   If admitted, relevant portions of the publication may be read into
evidence but may not be received as exhibits.

722.  (a) The fact of the appointment of an expert witness by the
court may be revealed to the trier of fact.
   (b) The compensation and expenses paid or to be paid to an expert
witness by the party calling him is a proper subject of inquiry by
any adverse party as relevant to the credibility of the witness and
the weight of his testimony.

723.  The court may, at any time before or during the trial of an
action, limit the number of expert witnesses to be called by any
party.