Expert Testimony, Qualifications of Experts

Under the Federal Rules of Evidence and virtually all state codes, expertise is defined by the nature and scope of the proffered opinion. The basic issue with regard to a qualifications assessment is whether the witness has the background to support his or her intended testimony. An expert must be qualified to “assist the trier of fact.” But no strict tests or minimum requirements apply to the assessment of qualified expertise. The level of qualifications required varies with the demands of the proffered testimony.

The Federal Rules of Evidence, for example, define qualifications broadly, encompassing “knowledge, skill, experience, training, or education.” In general, courts interpret the main qualifications requirement in relation to the expert's claimed expertise and the nature of the testimony. Hence, experts on medical matters are expected to have medical degrees, appropriate certifications, and experience, but auto mechanics or real estate appraisers might only need years of experience and demonstrable skills. Professional degrees or certifications, therefore, may be considered by courts because they reflect the expert's level of skill or experience but are not formal requirements of the rules. As a practical matter, courts typically consult the experts' respective fields for guidance regarding what constitutes a “qualified” expert. Not all fields, however, have well-articulated standards, and many subjects of interest to the law are studied by fields with widely varying professional requirements.

Because an expert's qualifications must be sufficient to support his or her intended testimony, courts regularly demand that experts possess certain minimal degree requirements or professional certifications before being allowed to testify. In a case presenting an issue of medical causation, for instance, a court is likely to require an expert to possess a medical degree. Similarly, testimony regarding structural engineering will typically be introduced through the testimony of a structural engineer. In most jurisdictions, the question of a particular expert's qualifications is within the discretion of the trial court and will not be overturned absent a finding that the lower court abused its discretion. Indeed, it is highly unusual for an appellate court to reverse a lower court's finding that a particular expert passes or fails the qualifications test.

With regard to fields with highly formalized credentialing requirements, courts tend to follow the respective field's expectations regarding what it takes to be “qualified.” This usually means that the courts mirror the respective fields from which the experts hail. If, for example, a field requires certification to practice the expertise, courts tend to assume that party experts from that field will possess the requisite certification. Experts who fail to meet their own field's qualifications demands are presumed unqualified by most courts. This, however, is a rebuttable presumption. Courts use a field's certification requirements as a guidepost for judging expertise, not as a prerequisite to receiving an expert's opinion. In effect, therefore, a field's certification requirement constitutes a factor, albeit an important one, in the assessment of qualifications.

Many expert fields, however, have no formal credential requirements, and the courts similarly follow the field's lead here too. Hence, medical experts usually must have attained the M.D. degree at a minimum, but experts on psychological subjects might possess a host of degrees or even experience-based specialization. For example, courts sometimes find experts with just a B.A. degree, together with significant work experience, to be minimally qualified to testify generally on subjects such as the battered woman syndrome or child abuse accommodation syndrome.

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