358 F. Supp. 3d 956
N.D. Cal.2019Background
- Plaintiffs (Hardeman, Gebeyehou, Stevick) seek to survive Monsanto's summary judgment by proving specific causation that glyphosate exposure caused their non‑Hodgkin's lymphoma (NHL).
- Court previously admitted plaintiffs' general‑causation experts finding glyphosate capable of causing NHL; this ruling addresses specific causation for three bellwether plaintiffs.
- Plaintiffs' specific‑causation experts relied on a differential‑diagnosis/etiology approach, clinical judgment, medical records review, exposure histories, and the admissible general‑causation opinions.
- Monsanto challenged the experts’ ruling‑in (cherry‑picking studies; lack of adjusted odds ratios >2.0) and ruling‑out (failure to exclude idiopathic causes and other risk factors).
- The court concluded the experts are admissible and plaintiffs have just enough evidence to present to a jury, but excluded several unreliable, quantitatively precise, or speculative aspects of their testimony (e.g., unadjusted thresholds, smoking analogy).
- Additional Daubert challenges remain for Phase 2 experts; some expert testimony exclusion/motion‑in‑limine rulings were referenced and will be addressed later.
Issues
| Issue | Plaintiff's Argument | Defendant's Argument | Held |
|---|---|---|---|
| Admissibility of differential diagnosis/etiology for specific causation | Experts may rely on clinical judgment, medical records, exposure, and admitted general‑causation opinions to conclude glyphosate was a substantial factor | Monsanto contends experts unreliably ruled in glyphosate (cherry‑picked studies) and failed to reliably rule out other causes | Court admitted the experts: Ninth Circuit permits broad latitude for clinical‑based differential etiology; experts may rely on admitted general‑causation opinions |
| Reliance on epidemiology and requirement of RR>2.0 | Plaintiffs say no categorical RR>2.0 requirement; totality of evidence and general causation suffices for specific causation | Monsanto urges that experts must show an adjusted RR>2.0 to assign causation to an individual | Court: No bright‑line RR>2.0 rule under California law; RR>2.0 can be dispositive but is not a categorical prerequisite to survive summary judgment |
| Addressing idiopathic cases and distinguishing which exposed patients were caused by glyphosate | Experts used exposure intensity, dose‑response literature, and clinical judgment to place these plaintiffs among those whose NHL was attributable to glyphosate | Monsanto argues experts failed to meaningfully distinguish idiopathic cases or provide biomarkers/signatures to exclude idiopathy | Court: Experts provided sufficient methodology (exposure levels, clinical experience, reliance on general causation) to let a jury decide; more speculative means of drawing lines excluded |
| Specific excluded opinion fragments (quantification & analogies) | Plaintiffs' experts offered quantitative thresholds (e.g., >2 days/yr or >10 lifetime days doubles risk) and analogies to smoking risk recognition | Monsanto argued those statements are based on unadjusted data or are speculative and misleading | Court excluded testimony quantifying causation based on unadjusted McDuffie/Eriksson figures and excluded smoking analogy as speculative and inadmissible under Rules 403/702 |
Key Cases Cited
- Wendell v. GlaxoSmithKline LLC, 858 F.3d 1227 (9th Cir. 2017) (permissive Ninth Circuit approach to clinical differential‑etiology testimony)
- Clausen v. M/V New Carissa, 339 F.3d 1049 (9th Cir. 2003) (framework for ruling in/ruling out causes in differential diagnosis)
- Messick v. Novartis Pharm. Corp., 747 F.3d 1193 (9th Cir. 2014) (recognizing medicine’s art and admitting borderline causation opinions)
- Tamraz v. Lincoln Elec. Co., 620 F.3d 665 (6th Cir. 2010) (distinguishing differential diagnosis/etiology terminology and approach)
- In re Lipitor Mktg., Sales Practices & Prods. Liab. Litig., 892 F.3d 624 (4th Cir. 2018) (more stringent evaluation of expert causation compared to Ninth Circuit)
- Daubert v. Merrell Dow Pharm., Inc., 43 F.3d 1311 (9th Cir. 1995) (discussing role of epidemiologic risk doubling evidence and expert testimony)
- Cooper v. Takeda Pharm. Am., Inc., 239 Cal. App. 4th 555 (Cal. Ct. App. 2015) (California law treating doubling of risk as significant for specific causation)