professional work in the field of biomechanics and engineering.” Ibid. There was “no indication in the record that the bases for Dr. Lafferty’s opinions were subjected to any kind of peer review or publication,” no basis on which to “consider the error rate” of Lafferty’s technique, and no basis for determining whether Lafferty’s “methods are consistent with the generally accepted method for gathering and evaluating evidence in the field of biomechanics and mechanical engineering as applied to occupant dynamics and restraint system efficacy in motor vehicle accidents.” Id. at 15. Because the court was “unable to determine what methodology or reasoning, if any, serves as the basis for Dr. Lafferty’s opinions,” and because “Lafferty offers nothing more than subjective belief and unsupported speculation,” his testimony was inadmissible under Rule 702. Id. at 15, 16, 18.
Second, the district court ruled that Lafferty’s testimony that Clark’s lap belt failed was inadmissible because it was “not helpful to the trier of fact.” NR 87:16; see Fed. R. Evid. 702. The court described as “problematic” the fact that
Dr. Lafferty assumes the very fact that Mr. Clark attempts to prove through his expert testimony: that the lap belt failed during the accident sequence. At his deposition, Dr. Lafferty testified that he was assuming that Mr. Clark’s lap belt unlatched during the accident sequence. He specifically testified that he did not address the question whether the lap belt became unlatched during the accident sequence. Because Dr. Lafferty assumes the very fact to be true that his expert testimony is offered to prove, his testimony is not helpful to the trier of fact in determining the same fact in issue.
NR 87:16 (emphasis added).
Third, the district court ruled that Lafferty’s testimony “regarding the relative lack of blood on the lap belt,” which Clark had offered “[i]n an effort to recover from Dr. Lafferty’s damaging testimony that [Lafferty] ha[d] assumed the lap belt became unlatched,” was inadmissible because it is both “unscientific speculation and not based