Source: https://www.hpylaw.com/publications/limitation-of-expert-trial-testimony-using-california-evidence-code-721-as-a-sword-and-shield/
Timestamp: 2019-04-25 17:42:35+00:00

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Almost all cases at trial require some form of expert testimony. Expert testimony is based, in part, by relying on literature, studies, and testing that supports the expert’s opinion. If you are using expert witness testimony to support your client’s case, chances are that the other party is too. If you try to exclude or limit the opposing counsel’s expert witness testimony, the other party will try to do the same with your expert witness.
What is your game plan for this inevitable battle of the motions and objections? That’s where California Evidence Code Section 721 comes into the fold. Section 721 may be used as a sword to exclude potential junk science from entering the courtroom. Similarly, it can be used as a shield to prevent impeachment or other forms of cross-examination of your experts on literature not used in forming their opinion.
Setting the Stage:In general, while an expert may state on direct examination the matters on which he or she relied (i.e. the name, date and author of the study) the expert may not testify as to the details of those matters if they are otherwise inadmissible. (People v. Nicolaus, 54 Cal.3d 551, 583 (1991)). An expert may not, under the guise of the reasoning behind his or her expert opinion, bring before the jury incompetent hearsay evidence. (People v. Coleman, 38 Cal.3d 69, 92 (1985); Furtado v. Montebello Unified School Dist., 206 Cal. App. 2d 72, 79-80 (1962) (an expert may not recite from textual material while testifying)). All too often, testifying experts cross the line between relaying their own opinions to the jury and relaying those opinions held by other non-testifying experts upon which they rely, without objection.
Furtado v. Montebello Unified School Dist., 206 Cal.App.2d 72, 79 (1962): it is an error to allow a doctor to testify as to details in individual case histories in medical journals to support his or her opinion.
Continental Airlines, Inc. v. McDonnell Douglas Corp., 216 Cal.App.3d 388, 416 (1989): while an expert may state on direct examination that he or she relied on information contained in certain reports, the expert may not testify as to the contents of such reports.
Grimshaw v. Ford Motor Co., 119 Cal.App.3d 757, 788 (1981): on direct examination, an automotive expert was not permitted to relay any details of reports regarding safety tests on which he based his opinion.
Tools of the Trade: There are a number of tools a trial attorney has at his or her disposal to combat this problem. First, one can raise a preemptive strike through use of an in limine motion. An in limine motion has the advantage of setting the groundwork at the outset of the presentation of evidence. This allows examinations to be tailored in scope ahead of time. The downside however, is that it puts the opposing party on notice and counsel then has the ability to tailor his or her questions in a particular manner. This may take away the element of surprise.
Second, raising an oral motion just prior to the expert’s examination may serve as a tactical advantage with the added element of surprise. The rationale is that if and when the limitation is granted, opposing counsel has prepared a direct outline based on at least some questions they may no longer ask. This could be particularly damaging to opposing counsel’s ability to effectively present evidence in the manner he or she so desires.
Upon proper objection, an expert should be limited to the fact he or she relied on particular piece of literature and the publishing information (name of author, date of publication, and where it appears), rather than allowing the expert to relay the opinions of others.
Evidence Code § 721 as a Shield: Often times, attorneys representing the opposing party will seek to bring to light materials helpful to their case on cross-examination, when your client’s expert did not rely on those materials. This tactic can affect a particular expert’s credibility and weight, as some jurors perceive the absence of reliance as a material omission.
However, an expert witness may not be cross-examined relating to content or tenor of text, treatise or journal, unless the witness “referred to, considered, or relied upon such publication in arriving at or forming his or her opinion.” (Evid. Code § 721(b)(1)). Thus, it is improper to allow reading from a text upon which an expert does not rely in forming their opinion. (McGarity v. Department of Transportation, 8 Cal. App. 4th 677, 684 (1992)). A party attacking the credibility of an expert may bring to the jury’s attention material that is relevant to an issue of which the expert was unaware, but that party may not by its questions testify regarding the content of that material. (People v. Visciotti, 2 Cal. 4th 1, 81, 825 P.2d 388 (1992); see also People v. Bell, 49 Cal.3d 502, 532 (1989)). As such, Section 721 can be used as a valuable tool to prevent the opposing party’s examination into materials not considered by your experts. This is especially useful when the material is not credible or generally relied upon by experts in the field.
Evidence Code § 721 as a Sword:Experts will often refer to unrelied upon materials in the course of explaining the reasons for their opinions. Because an opposing expert cannot be cross-examined on such material, a motion to strike or exclude portions of the testimony on certain subjects is proper. The groundwork for such an attack can be laid during expert’s deposition prior to trial. Typically, each expert provides a report with a list of reliance materials. However, Section 721’s limitation is in the alternative: i.e., “referred to, considered, or relied upon.” Therefore, when deposing an opposing party’s expert, it is prudent to ask whether the expert referred to or considered any material not present on their reliance list. This allows counsel to box in their testimony long before the witness ever takes the stand. When the expert later attempts to base his or her opinions on something other than what he or she admitted to considering, relying on, or referencing, you may move to exclude any such testimony or material.

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