332.Expert Witness Testimony
(A witness was/Witnesses were) allowed to testify as [an] expert[s] and
to give [an] opinion[s]. You must consider the opinion[s], but you are
not required to accept (it/them) as true or correct. The meaning and
importance of any opinion are for you to decide. In evaluating the
believability of an expert witness, follow the instructions about the
believability of witnesses generally. In addition, consider the expert’s
knowledge, skill, experience, training, and education, the reasons the
expert gave for any opinion, and the facts or information on which the
expert relied in reaching that opinion. You must decide whether
information on which the expert relied was true and accurate. You may
disregard any opinion that you ﬁnd unbelievable, unreasonable, or
unsupported by the evidence.
[An expert witness may be asked a hypothetical question. A hypothetical
question asks the witness to assume certain facts are true and to give an
opinion based on the assumed facts. It is up to you to decide whether an
assumed fact has been proved. If you conclude that an assumed fact is
not true, consider the effect of the expert’s reliance on that fact in
evaluating the expert’s opinion.]
[If the expert witnesses disagreed with one another, you should weigh
each opinion against the others. You should examine the reasons given
for each opinion and the facts or other matters on which each witness
relied. You may also compare the experts’ qualiﬁcations.]
New January 2006
When expert testimony is received at trial, the court must sua sponte instruct the
jury on evaluating the expert’s testimony. (Pen. Code, § 1127b.)
Give the bracketed paragraph beginning, “An expert witness may be asked a
hypothetical question,” if an expert witness responded to a hypothetical question.
Give the bracketed paragraph beginning, “If the expert witnesses disagreed with
one another,” if there is conﬂicting expert testimony.
• Instructional Requirements. Pen. Code, § 1127b.
5 Witkin & Epstein, California Criminal Law (3d ed. 2000) Criminal Trial, § 642.
1Witkin, California Evidence (4th ed. 2000) Opinion Evidence, § 85.