California Civil Jury Instructions (CACI)

219. Expert Witness Testimony

During the trial you heard testimony from expert witnesses. The law allows an expert to state opinions about matters in his or her field of expertise even if he or she has not witnessed any of the events involved in the trial.

You do not have to accept an expert’s opinion. As with any other witness, it is up to you to decide whether you believe the expert’s testimony and choose to use it as a basis for your decision. You may believe all, part, or none of an expert’s testimony. In deciding whether to believe an expert’s testimony, you should consider:

a. The expert’s training and experience;

b. The facts the expert relied on; and

c. The reasons for the expert’s opinion.

New September 2003

Directions for Use

This instruction should not be given for expert witness testimony on the standard of care in professional malpractice cases if the testimony is uncontradicted. Uncontradicted testimony of an expert witness on the standard of care in a professional malpractice case is conclusive. (Howard v. Owens Corning (1999) 72 Cal.App.4th 621, 632–633 [85 Cal.Rptr.2d 386]; Conservatorship of McKeown (1994) 25 Cal.App.4th 502, 509 [30 Cal.Rptr.2d 542]; Lysick v. Walcom (1968) 258 Cal.App.2d 136, 156 [65 Cal.Rptr. 406].) In all other cases, the jury may reject expert testimony, provided that the jury does not act arbitrarily. (McKeown, supra, 25 Cal.App.4th at p. 509.)

Do not use this instruction in eminent domain and inverse condemnation cases. (See Aetna Life and Casualty Co. v. City of Los Angeles (1985) 170 Cal.App.3d 865, 877 [216 Cal.Rptr. 831]; CACI No. 3515, Valuation Testimony.)

For an instruction on hypothetical questions, see CACI No. 220, Experts—Questions Containing Assumed Facts. For an instruction on conflicting expert testimony, see CACI No. 221, Conflicting Expert Testimony.

Sources and Authority

  • The “credibility of expert witnesses is a matter for the jury after proper instructions from the court.” (Williams v. Volkswagenwerk Aktiengesellschaft (1986) 180 Cal.App.3d 1244, 1265 [226 Cal.Rptr. 306].)
  • “ ‘Generally, the opinion of an expert is admissible when it is “[r]elated to a subject that is sufficiently beyond common experience that the opinion of an expert would assist the trier of fact . . . .” [Citations.] Also, “[t]estimony 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.” [Citation.] However, “ ‘Where the jury is just as competent as the expert to consider and weigh the evidence and draw the necessary conclusions, then the need for expert testimony evaporates.’ ” ’ Expert testimony will be excluded ‘ “ ‘when it would add nothing at all to the jury’s common fund of information, i.e., when ‘the subject of inquiry is one of such common knowledge that men of ordinary education could reach a conclusion as intelligently as the witness.” ’ ” ’ ” (Burton v. Sanner (2012) 207 Cal.App.4th 12, 19 [142 Cal.Rptr.3d 782], internal citations omitted.)
  • Under Evidence Code section 801(a), expert witness testimony “must relate to a subject that is sufficiently beyond common experience that the opinion of an expert would assist the trier of fact.” (New v. Consolidated Rock Products Co. (1985) 171 Cal.App.3d 681, 692 [217 Cal.Rptr. 522].)
  • Evidence Code section 720(a) provides, in part: “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.”
  • Expert witnesses are qualified by special knowledge to form opinions on facts that they have not personally witnessed. (Manney v. Housing Authority of The City of Richmond (1947) 79 Cal.App.2d 453, 460 [180 P.2d 69].)
  • “Although a jury may not arbitrarily or unreasonably disregard the testimony of an expert, it is not bound by the expert’s opinion. Instead, it must give to each opinion the weight which it finds the opinion deserves. So long as it does not do so arbitrarily, a jury may entirely reject the testimony of a plaintiff’s expert, even where the defendant does not call any opposing expert and the expert testimony is not contradicted.” (Howard, supra, 72 Cal.App.4th at p. 633, citations omitted.)

Secondary Sources

1 Witkin, California Evidence (4th ed. 2000) Opinion Evidence, §§ 26–44

Jefferson, California Evidence Benchbook (3d ed. 1997) §§ 29.18–29.55

1 Levy et al., California Torts, Ch. 3, Proof of Negligence, § 3.04 (Matthew Bender)

3A California Trial Guide, Unit 60, Opinion Testimony, § 60.05 (Matthew Bender) California Products Liability Actions, Ch. 4, The Role of the Expert, § 4.03 (Matthew Bender)

48 California Forms of Pleading and Practice, Ch. 551, Trial, §§ 551.70, 551.113 (Matthew Bender)