Expert Witness Testimony: Fed.R.Evid. 702-705 Primer; Hypothetical Question Discretionary Use

This article is the second of a series of three articles on lay and expert witness testimony. The focus of the series of articles is in significant part upon the testimony of law enforcement officials in criminal cases. The first article examined the prosecution calling of law enforcement officials under the guise of lay witness testimony to render opinion testimony, a practice supported by the Department of Justice, thus avoiding expert witness disclosure and reliability requirements in spite of the amendment to Fed.R.Evid. 701 clearly distinguishing lay from expert witness testimony. It also explained and critiqued the concepts of “particularized knowledge” “skilled” and “treating physician” lay witness opinion testimony along with proposing the concept of “specific knowledge” expert witness testimony. The current article is a primer on expert witness testimony addressed to attorneys trying criminal cases under the Federal Rules of Evidence or state evidence codes modeled thereon highlighting the critical operative components of Fed.R.Evid. 702-705. The last article, building on the initial articles in this set, will examine recent expressions in several federal court of appeals decisions that the prosecution sometimes in presenting overview, course of investigation, explanation of terms, and summary law enforcement expert testimony, and occasionally lay witness law enforcement testimony, has done so in violation of the Federal Rules of Evidence and Confrontation Clause. Testimony providing scientific, technical, or other specialized knowledge, in the form of an opinion or otherwise, is admissible only if (1) the knowledge is based upon sufficient facts, data, or opinions, (2) there are sufficient assurances of trustworthiness present that the explanative theory being employed to create the knowledge produces a correct result to warrant jury acceptance, i.e., a product of reliable principles and methods, (3) the explanative theory has been applied in accordance with proper procedures, (4) the witness is qualified as an expert by knowledge, skill, experience, training or education to provide such knowledge, and (5) the knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, Fed.R.Evid. 702. The admissibility of expert testimony, Fed.R.Evid. 702, requires that the trial court make several preliminary determinations, Fed.R.Evid. 104(a). The trial court must decide whether the witness called is properly qualified to give the testimony sought. A witness may be qualified as a expert on the basis of either knowledge, skill, experience, training, or education or a combination thereof. The trial court must further determine that the testimony of the expert witness, in the form of an opinion or otherwise, will assist the trier of fact, i.e., be helpful, to understand the evidence or to determine a fact in issue, Fed.R.Evid. 702(a). Finally, the trial court must determine that as actually applied in the matter at hand, Fed.R.Evid. 702(d), to facts, data, or opinions sufficiently established to exist, Fed.R.Evid. 702(b), including facts, data, or opinions reasonably relied upon under Fed.R.Evid. 703, sufficient assurances of trustworthiness are present that the expert witness' explanative theory produces a correct result to warrant jury acceptance, i.e., a product of reliable principles and methods, Fed.R.Evid. 702(c). An explanative theory must be supplied by the expert; an opinion without analysis is meaningless. The proponent of the expert witness testimony has the burden of establishing the foregoing admissibility requirements to be more probably true than not true. The weight to be given to expert testimony permitted by the court is for the trier of fact to determine. Expert witness testimony is subject to exclusion under Fed.R.Evid. 403. Expert testimony is not limited to scientific or technical areas, but rather includes all areas of specialized knowledge. With respect to personal knowledge obtained through training and experience not possessed by the average person acquired as an actor or viewer of a specific circumstance relevant to the litigation improperly being admitted as lay witness opinion testimony and not treated as it should be as “specific knowledge” expert witness opinion testimony, see Graham, “Lay Opinion Testimony and Expert Opinion Testimony Differentiated: ‘Specific Knowledge’ Expert Witness Opinion Testimony; Proposed Amendments to Fed.R.Crim.Proc. 16(a)(1)(G) and Fed.R.Evid. 701 and 702”, — Crim.L.Bull. — (2016). When scientific, technical, or other specialized knowledge will be helpful to the trier in evaluating facts intelligently, the traditional method of supplying data of this nature is the introduction of an opinion of an expert witness. Fed.R.Evid. 702 provides that expert testimony may be “in the form of an opinion or otherwise.” Thus the expert may, but need not, testify in the form of an opinion. He may instead give an exposition of relevant scientific or other principles permitting the trier of fact to draw its own inference or conclusion from the evidence presented, or he may combine the two. The expert whose function is to supply scientific, technical or other specialized knowledge, should be distinguished from the lay witness who is required to have some specific background of experience common to many human beings in order to render his observations significant, i.e., rationally based on the perception of the witness as specified in Fed.R.Evid. 701. What is required of the expert witness is the establishment of a sufficiently reliable explanative theory underlying scientific, technical, or other specialized knowledge that will assist the trier of fact to understand the evidence or determine a fact in issue. See generally Graham, Handbook of Federal Evidence, §§ 702.5, 702.6 (8th ed. 2017).