Taking a "Hard Look" at Expert Witness Testimony Under Rule 702.

• Author: Sahu, Munjot
• Position: Federal Rules of Evidence - Mirena IUS Levonorgestrel-Related Product Liability Litigation, In re

IN pharmaceutical and medical device product liability litigation, state substantive law invariably requires a plaintiff to proffer reliable expert witness testimony that the drug or device at issue proximately caused the injury allegedly sustained by the plaintiff. Rule 702 of the Federal Rules of Evidence provides that expert testimony is admissible only if a party's expert witness is "qualified as an expert by knowledge, skill, experience, training, or education," and the potential expert testimony meets four requirements: (1) the expert's scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence or to determine a fact in issue; (2) the testimony is based on sufficient facts or data; (3) the testimony is the product of reliable principles and methods; and (4) the expert has reliably applied the principles and methods to the facts of the case. Because the exclusion of expert testimony may be dispositive of, or significantly narrow, a plaintiff's case, issues concerning its admissibility are hotly contested in virtually every pharmaceutical and medical device product liability lawsuit. Litigation over whether a drug or device can cause, and in fact did cause, a plaintiff's alleged injury routinely involves a "battle of the experts" in the fields of epidemiology, pharmacology, toxicology, biostatistics, and other complex scientific disciplines. And judges--who often have little to no scientific educational background or training--must act as gatekeepers in navigating these complex subject areas to ensure that juries consider only reliable scientific evidence.

When making Rule 702 determinations, federal district courts often rely on Daubert v. Merrell Dow Pharmaceuticals, Inc. (1) and its progeny, which articulate a non-exhaustive list of factors ("Daubert factors") to consider: (l) whether the theory or technique in question can be and has been tested; (2) whether it has been subjected to peer review and publication; (3) its known or potential error rate and the existence and maintenance of standards controlling its operation; and (4) whether it has attracted widespread acceptance within a relevant scientific community. (2) Unfortunately, the complexity of applying these legal standards to science, coupled with a deferential "abuse of discretion" standard of appellate review, has resulted in nearly 30 years of unpredictable, conflicting results due to inconsistent, and sometimes incorrect, judicial application of Daubert and Rule 702.

The Second Circuit's appellate decision in In re Mirena IUS Levonorgestrel-Related Prod. Liab. Litig. (No. II), (3) however, offers promising guidance that may help unify trial courts in the proper application of Daubert and Rule 702. There, the court affirmed the exclusion of all seven of Plaintiffs' general causation experts from testifying in the Mirena[R] product liability multidistrict litigation ("MDL"), finding their proffered testimony inadmissible under the Daubert standard. Notably, the court emphasized that to uphold their gatekeeping function, federal trial courts must take a "hard look" at an expert's proffered testimony and undertake a rigorous examination to ensure that the expert's methodology is "reliable at every step of the way." (4) This article examines the Mirena opinion and underlying trial court decision; analyzes the decision's influence to-date; and predicts Mirena's future impact considering the pending Rule 702 Amendments.

1. The "Hard Look"

   The Mirena Intrauterine System ("Mirena") is a plastic T-shaped intrauterine device, manufactured by Bayer, that releases a synthetic steroid hormone called levonorgestrel ("LNG") into the uterus to prevent pregnancy. In re Mirena IUS Levonorgestrel-Related Prod. Liab. Litig. (No. II) was an MDL consolidating consumers' claims that LNG released by their use of the Mirena caused them to develop idiopathic intracranial hypertension ("IIH")--a rare disorder marked by increased cerebrospinal fluid pressure in the brain. (5) Like other recent mass tort MDLs, the U.S. District Court for the Southern District of New York prioritized...