UNITED STATES DISTRICT COURT
For the Eastern District of Pennsylvania
Civil Action No. 25-CV-3194
DEFENDANT'S MOTION IN LIMINE TO EXCLUDE PLAINTIFF'S EXPERT TESTIMONY
I. INTRODUCTION
Defendant respectfully moves this Court to exclude the proposed testimony of Plaintiff's expert, Dr. Helena Vargas, on the question of medical causation. The proffered opinion fails the reliability gatekeeping standard set forth in Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993), which requires the trial court to ensure that expert testimony is both relevant and reliable before it reaches the jury.
II. LEGAL STANDARD
Under Daubert, 509 U.S. at 593-94, the trial court considers (1) whether the theory or technique can be tested, (2) whether it has been subjected to peer review and publication, (3) the known or potential rate of error, (4) the existence and maintenance of standards controlling the technique's operation, and (5) the degree of acceptance within the relevant scientific community. The 2023 amendments to Federal Rule of Evidence 702 codify these factors.
The gatekeeping obligation extends beyond purely scientific testimony. In Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999), the Supreme Court held that Daubert's general gatekeeping obligation applies not only to testimony based on scientific knowledge but also to testimony based on technical and other specialized knowledge. Dr. Vargas's opinion is therefore subject to the same exacting reliability inquiry.
III. ARGUMENT
A. The District Court's Gatekeeping Determination Is Reviewed for Abuse of Discretion
Under General Electric Co. v. Joiner, 522 U.S. 136 (1997), this Court's reliability determination is reviewed under the deferential abuse-of-discretion standard. A district court may exclude expert testimony when there is simply too great an analytical gap between the data and the opinion proffered — which is precisely the deficiency here.
B. Dr. Vargas's Causation Opinion Fails the Reliability Inquiry
Dr. Vargas relies on three animal studies and a single in vitro experiment to support her general causation opinion. None of these studies has been peer-reviewed in the relevant clinical literature, and Dr. Vargas concedes that no epidemiological evidence supports her conclusion. Under Joiner, 522 U.S. at 146, "nothing in either Daubert or the Federal Rules of Evidence requires a district court to admit opinion evidence that is connected to existing data only by the ipse dixit of the expert." That is the case here.
C. Plaintiff Cannot Cure the Reliability Defect at Trial
Decades of caselaw following Daubert place parties on notice of the exacting reliability standards expert evidence must meet. As Weisgram v. Marley Co., 528 U.S. 440 (2000) makes clear, plaintiffs bear the burden of marshaling reliable expert proof before trial. The Court should not permit Dr. Vargas's deficient methodology to reach the jury.
CONCLUSION
For the foregoing reasons, Defendant respectfully requests that this Court grant the motion in limine and exclude Dr. Vargas's testimony on medical causation in its entirety.