Handwriting Expert's Testimony Need Not Be Given to "Reasonable Degree of Scientific Certainty," Third Circuit Holds

In a published decision, the Third Circuit has held that a trial court committed no plain error in permitting a government handwriting identification expert to testify that her opinions were held to a "reasonable degree of scientific certainty." From the opinion:

As the Government has pointed out, . . . "there is nothing magical about the phrase, 'to a reasonable degree of scientific certainty.'" It is not derived from the language of Rule 702 itself, and this Court has been unable to find any authority to support the position that questions regarding the expert's "degree of scientific certainty" categorically renders expert testimony inadmissible.

Handwriting experts often give their opinions in terms of probabilities rather than certainties. See, e.g., United States v. Rosario, 118 F.3d 160, 163 (3d Cir. 1997) (considering a handwriting expert's testimony that the defendant "probably" authored a forged check in affirming a forgery conviction); United States v. McGlory, 968 F.2d 309, 346 (3d Cir. 1992) (handwriting testimony is admissible "even if the handwriting expert is not absolutely certain that the handwriting is that of the defendant."); United States v. Galvin, 394 F.2d 228, 229 n.1 (3d Cir. 1968) (handwriting testimony is not rendered inadmissible merely "because it expresses a probability"). Indeed, Jackson testified that rendering "less-than-certain" opinions is an accepted practice in her field. We therefore find no error (let alone a plain error) in the District Court's decision to allow Jackson's testimony and to allow the jury to determine what weight to give her "less-than-certain" conclusions. See McGlory, 968 F.2d at 346 ("Any issue regarding the certainty of [the handwriting expert's] testimony goes to the weight given that testimony and could be tested by cross-examination."); Galvin, 394 F.2d at 229 n.1 ("reservations in the expressed opinion . . . go to the weight of the evidence and are a determination for the jury or fact-finder to make. . . .").

See United States v. Mornan, No. 04-1319 (3d Cir. June 30, 2005) (Ambro, Van Antwerpen, & Tashima, JJ.).