§ 24.02 SUBJECT MATTER REQUIREMENT: AN OVERVIEW

• Jurisdiction: United States

§ 24.02. SUBJECT MATTER REQUIREMENT: AN OVERVIEW

Federal Rule 702 specifies the subject matter requirement for expert testimony. One commentator noted that this requirement raises two distinct issues: "The field of expertness is bounded on one side by the great area of the commonplace, supposedly within the ken of every person of moderate intelligence, and on the other by the even greater area of the speculative and uncertain."² A chart illustrates these two aspects of the subject matter requirement:

Boundaries A and B raise different issues. Thus, the evidentiary standards for these two boundaries differ. One standard is required for instances where expertise is not needed — i.e., the commonplace, and another standard for judging when the testimony is too unreliable or uncertain.

As enacted in 1975, Rule 702 dealt only with boundary B. Instead of adopting the common law formulation ("beyond the ken of a lay jury"), the Rule employs a "help-the-jury" standard, which was thought to be somewhat more liberal in terms of admissibility. Because an evidentiary standard for boundary A was not included, the lower courts (and eventually the Supreme Court) were required to address the issue, i.e., Daubert and the 2000 amendment to Rule 702, which are discussed in § 24.04.

The trial judge decides whether a subject is a proper one for expert testimony.³ The judge has "broad discretion in the matter of the admission or exclusion of expert evidence, and his action is to be sustained unless manifestly erroneous."⁴ As the Supreme Court noted, "The Rules of Evidence — especially Rule 702 — do assign to the trial judge the task of ensuring that an expert's testimony both rests on a reliable foundation and is relevant to the task at hand."⁵

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Notes:

^[2] Maguire, Evidence: Common Sense and Common Law 30 (1947). He also noted: "Of course both these boundaries constantly shift, as the former area enlarges and the latter diminishes. Only a few years ago it would have been necessary to take expert evidence on issues with respect to the operation of motor cars, airplanes, or radio which are now so completely inside the domain of popular understanding that such evidence would be rejected as superfluous. A century ago purportedly expert evidence on these topics would have been rejected as visionary." Id. X rays are another example. A radiologist may be...