Intense Daubert Hearings in Paraquat MDL Await Judge Rosenstengl’s Crucial Decision

The hearings on the Daubert motions took place from August 21-24 before MDL Judge Nancy Rosenstengl. The oral arguments were, as expected, very contentious and at a very high level. The sole live witness at the hearing, specifically requested by the Judge, was Dr. Michael Wells, plaintiffs’ only general causation expert.  The parties’ arguments on their respective motions to exclude other expert witnesses did not generate anywhere near the same time and heat as the arguments over Dr. Wells — which only makes sense since he is the linchpin of plaintiffs’ case.

Dr. Wells did a meta-analysis of seven (7) prior epidemiological studies of the causal link between exposure to Paraquat and Parkinson’s Disease, and he concluded that the odds ratio was 2.8. Syngenta and Chevron argued that he failed to properly consider let alone give proper weight to three more recent and much larger epidemiological studies, which did not show a causal link between Paraquat and Parkinson’s Disease — and used defendant boilerplate words such as “cherry-picking” to characterize his analysis as unreliable and thus warranting exclusion.  Dr. Wells and plaintiffs’ counsel Eric Kennedy strongly rebutted those attacks, emphasizing Dr. Wells did consider the other studies but gave them no weight in his analysis because they were lower quality and designed differently than the particular studies he relied upon.

Defendants also cited three prior litigations where Dr. Wells’ expert opinions had been allegedly excluded but plaintiffs’ counsel Kennedy seemed to adequately rebut those assertions as gross mischaracterizations.

In her questioning of counsel during the hearings, Judge Rosenstengl brought up the Seventh Circuit’s Manpower ruling (where that Court had reversed a district court judge for improperly excluding an expert on a Daubert motion). The language in that Seventh Circuit opinions warns district court judges not to overstep their limited role as “gatekeeper” on Daubert motions and intrude on the exclusive province of the jury as sole arbiter of the credibility and weight of expert witnesses’ opinions The Judge’s references to Manpower seemed somewhat heartening, signaling that she intends to tread carefully while wrestling with the critical question of allowing or excluding Dr. Wells and the other experts (on both sides).

At her request the parties filed 20-page post-hearing briefs on September 8, 2023.

She warned that she had much additional reading, and rereading, to do and, consequently, booted the upcoming October date for the first bellwether trial to some as-yet-unknown future date – all premised of course on her denying the Daubert motions aimed at excluding Dr. Wells (and excluding plaintiffs’ other expert witnesses) This is the third rescheduling of the trial.

It’s extremely hard to handicap the outcome of the Daubert motion aimed at Dr. Wells. The Judge did not appear to be anywhere close to making up her mind, or even leaning in one direction, by the end of the hearings.

Rulings on all the Daubert motions will hopefully be issued before year end.