This article originally appeared in the March/April 2017 issue of San Diego Lawyer.
Expert evidence can be front and center in any case, but it becomes crucial in science- and technology-intensive cases. The complexity associated with finding, preparing and correctly using the right experts can be high.
The most common use of experts is to offer a testifying expert’s opinion on the merits of a claim or defense. But a party may also use a consulting expert behind the scenes to help understand the facts and evaluate strengths and weaknesses of a case; assess the damages; prepare discovery; conduct electronic, particularly, forensic, discovery; prepare for depositions; challenge the opposing expert; and plan the trial.
To make the most use of the expert’s help, the first conversation with the plaintiff’s expert often takes place before the case is filed, and with the defendant’s expert early in discovery.
Choosing an Expert
The starting point is to identify the relevant area of expertise and necessary qualifications. Relatively minor gaps in qualifications, however, will generally not result in exclusion, and may be found to go to the weight of the evidence and be addressed through opposing expert’s testimony or cross-examination.
It is also important to check potential conflicts that may result in exclusion or prevent the expert from accessing the other side’s confidential information under the protective order. For example, an expert who actively researches and publishes in a certain area of technology may not be allowed to access a party’s confidential information related to that technology field.
Challenges to Expert Testimony
Expert evidence differs from fact evidence in a key aspect: expert evidence is an opinion that does not have to be based on the expert’s personal knowledge. Experts rely on their training, experience and methodology. Therefore, the admissibility of this opinion is regulated through a special set of rules designed to ensure its reliability. In federal court, the admissibility of expert testimony is governed by Federal Rule of Evidence 702 and Daubert v. Merrell Down Pharmaceuticals, 509 U.S. 579 (1993).
Overall, the admissibility standard is relatively lenient. In addition to the gatekeeping role of the court under Rule 702 and Daubert, the flaws in the expert evidence are regulated through the adversarial process itself: cross-examination, burden of proof and opposing expert — as well as court oversight.
The most successful challenges under Rule 702 are based on the expert’s methodology, but the other grounds — lack of qualifications, helpfulness to the trier of fact and sufficient factual support — should not be overlooked.
Helpfulness of the Expert’s Opinion
The specialized knowledge is admissible as long as it helps the jury understand the facts. Some knowledge of the subject matter by the jury is often expected and will not by itself preclude the expert opinion if it helps the jury further understand the issues.
Certain types of subject matter are generally outside experts’ purview. Most notably, expert testimony cannot be used for statutory interpretation or legal conclusions.
Expert testimony is not a substitute for jury instructions, and legal conclusions by an expert would supplant, instead of aid, the trier of fact. The expert, however, may opine on issues that embrace the ultimate conclusion. For example, although overall interpretation of a contract is a legal issue, expert testimony may be admissible regarding the meaning of a specialized term in the contract. In addition, experts cannot testify regarding credibility of a witness, although they may offer specialized knowledge that may bear on the jury’s conclusion regarding credibility.
Support for the Opinion
Experts are allowed to make assumptions and to extrapolate. But the evidence cannot be so scarce as to present a jump to conclusions. It also helps to have the expert conduct an independent test or investigation and not limit his support to sources that may appear biased.
Often, however, the factual basis of an expert opinion is viewed as going to the weight of the testimony, and not its admissibility.
Reliability of the Expert’s Methodology
The reliability of the expert’s methodology and its application to the facts is the primary concern with expert testimony. This is the area where the expert needs to be the most careful and the opposing counsel will likely be the most watchful.
The expert needs to articulate the methodology and explain its application. The methodology needs to comply with any legal requirements. Novel methodologies, although not automatically discredited, should be used with care, because they are more open to attack. As with any expert testimony, relatively minor issues with the methodology, such as treatments of particular sets of data, may be left to the adversarial process.