a visual inspection.” Hudgens Memorandum Opinion at 19. In Crawford, the district court stated simply that it found no “factual basis” for McSwain’s conclusion regarding the cracks’ visibility to the naked eye. Crawford Memorandum Opinion at 14. In reviewing these determinations for abuse of discretion, we are mindful of the repeated emphasis the Supreme Court has placed upon the district court’s “gatekeep-ing” role in the determination of whether expert evidence should be admitted. See Kumho Tire Co. v. Carmichael, 526 U.S. 137, 152, 119 S.Ct. 1167, 143 L.Ed.2d 238 (1999) (concluding “that the trial judge must have considerable leeway in deciding in a particular case how to go about determining whether particular expert testimony is reliable”); Joiner, 522 U.S. at 146, 118 S.Ct. 512 (<HOLDING>). Even when a decision to strike expert
holding that an expert opinion on a question of law is inadmissible holding district court is not required to admit opinion evidence that is connected to existing data only by the ipse dixit of the expert recognizing that while a testifying expert may rely upon facts or data made known to the expert before the hearing and even may rely upon opinions if reasonably relied upon by experts in the particular field the ipse dixit of that reliance does not make those facts data or opinions true particularly where  they are derived largely from hearsay recognizing district courts authority to exclude opinion evidence that is connected to existing data only by the ipse dixit of the expert should it conclude that there is simply too great an analytical gap between the data and the opinion proffered holding agency may not rely on expert opinion without disclosing hard data supporting opinion to the public