Rule 2:702.TESTIMONY BY EXPERTS (Rule 2:702(a)(i) derived from Code § 8.01- 401.3(A))

Rule 2:702 sets the threshold for letting an expert testify. In a civil proceeding, subdivision (a)(i) admits expert testimony whenever scientific, technical, or other specialized knowledge will assist the trier of fact in understanding the evidence or determining a fact in issue, and the witness is qualified as an expert by knowledge, skill, experience, training, or education. That qualification list is disjunctive — a witness can qualify through practical experience alone, without formal education, or through any combination of the five sources.

Criminal cases carry an added requirement. Subdivision (a)(ii) admits expert testimony only if the civil standard is met and the court also finds that the subject matter is beyond the knowledge and experience of ordinary persons, such that the jury needs the expert’s opinion to comprehend the subject matter, form an intelligent opinion, and draw its own conclusions. That extra finding reflects a more demanding gatekeeping role for expert testimony offered in criminal proceedings.

Subdivision (b) constrains the form the expert’s opinion may take. The testimony may consist of opinions the expert holds with a reasonable degree of probability, or it may address empirical data from which that probability can be established in the mind of the fact-finder. Two things are off-limits regardless of qualification: speculative testimony, and testimony that opines on the credibility of another witness — a judgment the rule reserves for the trier of fact.