Hempstead v. Pfizer, Inc.
150 F. Supp. 3d 644
D.S.C.2015Background
- This MDL bellwether concerns whether Lipitor (atorvastatin) caused Juanita Hempstead’s new‑onset Type 2 diabetes; plaintiffs must prove general and specific causation.
- Plaintiff disclosed two case‑specific experts; the court addresses defendant Pfizer’s Daubert challenge to Dr. Elizabeth Murphy.
- Dr. Murphy (endocrinologist) opined Lipitor was a substantial contributing cause, relying primarily on (1) population studies showing increased diabetes risk (she estimated RR ≈ 1.6) and (2) temporal sequence (Hempstead took Lipitor before diagnosis).
- Hempstead had multiple independent, significant diabetes risk factors: overweight/obesity (BMI ~26–29), substantial adult weight gain, age, hypertension, family history, and possible metabolic syndrome.
- Dr. Murphy did not quantify or rank the relative contribution of Lipitor versus other risks, could not identify any biological marker distinguishing statin‑caused diabetes, and admitted she effectively treated causation as ‘‘if on Lipitor and then diabetes, Lipitor contributed.’'
Issues
| Issue | Plaintiff's Argument | Defendant's Argument | Held |
|---|---|---|---|
| Admissibility of Dr. Murphy’s specific‑causation opinion under Rule 702/Daubert | Murphy used a common differential‑diagnosis approach and relied on (1) epidemiologic evidence of increased risk and (2) temporal relationship to Hempstead’s diagnosis | Murphy’s methodology is unreliable: it rests on post hoc temporal reasoning and fails to rule in/out or quantify alternative causes given many stronger risk factors | Excluded — court finds methodology unreliable and opinion unsupported by sufficient facts/data; Daubert/R.702 violation |
| Whether population‑level relative risk (RR ≈ 1.6) can, by itself, establish specific causation | Plaintiff argues RR shows Lipitor increases diabetes risk and, with temporal link, supports case‑specific causation | Defendant contends RR < 2.0 cannot, without further valid methodology, establish that Lipitor more likely than not caused Hempstead’s diabetes | Court: RR ~1.6 does not prove specific causation; it implies most cases would have occurred without Lipitor, so expert must show plaintiff is in minority attributable to drug; Murphy did not do so |
| Permissibility of using temporal proximity as dispositive proof of causation | Plaintiff emphasizes temporal relationship and literature showing plausibility | Defendant argues temporal proximity alone is insufficient and susceptible to post hoc fallacy, especially with multiple alternative causes | Court: Temporal proximity here is not compelling (onset ~5 years after start); reliance on timing alone is insufficient and invalidates Murphy’s conclusion |
| Reliability of differential‑diagnosis methodology as applied | Plaintiff asserts differential diagnosis is accepted and can support causation even without ruling out every alternative | Defendant says Murphy failed to apply differential diagnosis properly—no ranking/quantification or reasoned exclusion of other causes | Court: Differential diagnosis must be reliably applied; Murphy’s application was conclusory and failed to explain why other substantial risks were not the actual cause, so excluded |
Key Cases Cited
- Daubert v. Merrell Dow Pharm., 509 U.S. 579 (establishes district court gatekeeping for expert testimony under Rule 702)
- Westberry v. Gislaved Gummi AB, 178 F.3d 257 (4th Cir.) (distinguishes general vs. specific causation and discusses when temporal proximity may be compelling)
- Guinn v. AstraZeneca Pharm. LP, 602 F.3d 1245 (11th Cir.) (upheld exclusion where expert relied on temporal proximity and failed to rule out alternatives; risk‑factor aggregation insufficient)
- McClain v. Metabolife Int’l, Inc., 401 F.3d 1233 (11th Cir.) (Temporal relationships alone do not establish causation; cautions against post hoc reasoning)
- Cooper v. Smith & Nephew, Inc., 259 F.3d 194 (4th Cir.) (differential diagnosis must use a valid methodology and be reliably applied to be admissible)
- Viterbo v. Dow Chem. Co., 826 F.2d 420 (5th Cir.) (expert may not simply pick the cause most advantageous to plaintiff when multiple possible causes exist)