From Cason v. State Farm Fire & Cas. Ins. Co., 2011 U.S. Dist. LEXIS 108534 (E.D. La. Sept. 21, 2011):

When expert testimony is challenged under Daubert, the burden of proof rests with the party seeking to present the testimony. Moore v. Ashland Chem., Inc., 151 F.3d 269, 276 (5th Cir. 1998). To meet this burden, a party cannot simply rely on its expert's assurances that he has utilized generally accepted scientific methodology. Rather, some objective, independent validation of the expert's methodology is required. Id. Nonetheless, as Judge Vance stated in Scordill v. Louisville Ladder Group, L.L.C., 2003 WL 22427981, at *3 (E.D. La. Oct. 24, 2003):

The Court notes that its role as a gatekeeper does not replace the traditional adversary system and the place of the jury within the system. See Daubert, 509 U.S. at 596. As the Daubert Court noted, "[v]igorous cross-examination, presentation of contrary evidence, and careful instruction on the burden of proof are the traditional and appropriate means of attacking shaky but admissible evidence." Id. (citing Rock v. Arkansas, 483 U.S. 44, 61, 107 S. Ct. 2704, 97 L. Ed. 2d 37 (1987)). The Fifth Circuit has added that, in determining the admissibility of expert testimony, a district court must defer to "'the jury's role as the proper arbiter of disputes between conflicting opinions. As a general rule, questions relating to the bases and sources of an expert's opinion affect the weight to be assigned that opinion rather than its admissibility and should be left for the jury's consideration.'" United States v. 14.38 Acres of Land, More or Less Sit. in Leflore County, Miss., 80 F.3d 1074, 1077 (5th Cir. 1996) (quoting Viterbo v. Dow Chemical Co., 826 F.2d 420, 422 (5th Cir. 1987).

With respect to determining the relevancy of an expert's testimony pursuant to Rule 702 and Daubert, the proposed testimony must be relevant "not simply in the way all testimony must be relevant [pursuant to Rule 402], but also in the sense that the expert's proposed opinion would assist the trier of fact to understand or determine a fact in issue." Bocanegra v. Vicmar Servs., Inc., 320 F.3d 581, 584 (5th Cir. 2003). "'There is no more certain test for determining when experts may be used than the common sense inquiry whether the untrained layman would be qualified to determine intelligently and to the best degree the particular issue without enlightenment from those having a specialized understanding of the subject involved in the dispute.’” Vogler v. Blackmore, 352 F.3d 150, 156 n.5 (5th Cir. 2003) (quoting Fed. R. Evid. 702 advisory committee's note).