2005 California Evidence Code Sections 800-805 Article 1. Expert and Other Opinion Testimony Generally

800.  If a witness is not testifying as an expert, his testimony in
the form of an opinion is limited to such an opinion as is permitted
by law, including but not limited to an opinion that is:
   (a) Rationally based on the perception of the witness; and
   (b) Helpful to a clear understanding of his testimony.
801.  If a witness is testifying as an expert, his testimony in the
form of an opinion is limited to such an opinion as is:
   (a) Related to a subject that is sufficiently beyond common
experience that the opinion of an expert would assist the trier of
fact; and
   (b) Based on matter (including his special knowledge, skill,
experience, training, and education) perceived by or personally known
to the witness or made known to him at or before the hearing,
whether or not admissible, that is of a type that reasonably may be
relied upon by an expert in forming an opinion upon the subject to
which his testimony relates, unless an expert is precluded by law
from using such matter as a basis for his opinion.
802.  A witness testifying in the form of an opinion may state on
direct examination the reasons for his opinion and the matter
(including, in the case of an expert, his special knowledge, skill,
experience, training, and education) upon which it is based, unless
he is precluded by law from using such reasons or matter as a basis
for his opinion.  The court in its discretion may require that a
witness before testifying in the form of an opinion be first examined
concerning the matter upon which his opinion is based.
803.  The court may, and upon objection shall, exclude testimony in
the form of an opinion that is based in whole or in significant part
on matter that is not a proper basis for such an opinion.  In such
case, the witness may, if there remains a proper basis for his
opinion, then state his opinion after excluding from consideration
the matter determined to be improper.
804.  (a) If a witness testifying as an expert testifies that his
opinion is based in whole or in part upon the opinion or statement of
another person, such other person may be called and examined by any
adverse party as if under cross-examination concerning the opinion or
statement.
   (b) This section is not applicable if the person upon whose
opinion or statement the expert witness has relied is (1) a party,
(2) a person identified with a party within the meaning of
subdivision (d) of Section 776, or (3) a witness who has testified in
the action concerning the subject matter of the opinion or statement
upon which the expert witness has relied.
   (c) Nothing in this section makes admissible an expert opinion
that is inadmissible because it is based in whole or in part on the
opinion or statement of another person.
   (d) An expert opinion otherwise admissible is not made
inadmissible by this section because it is based on the opinion or
statement of a person who is unavailable for examination pursuant to
this section.
805.  Testimony in the form of an opinion that is otherwise
admissible is not objectionable because it embraces the ultimate
issue to be decided by the trier of fact.