Speaking of the United States’ newly ratified Constitution, Benjamin Franklin wrote in 1789: “in this world nothing can be said to be certain, except death and taxes.”  We would like to add to this list another certainty—summary judgment in a drug case without expert proof of general causation.  So, when the court excluded all of plaintiffs’ causation experts late last year, the writing was on the wall.  The court then disposed of a belated nuisance expert. Now, the other shoe has dropped in In re: Acetaminophen – ASD-ADHD Products Liability Litigation, 2024 WL 3874183 (S.D.N.Y. Aug. 20, 2024).

The Acetaminophen MDL concerned allegations that pre-natal use of the over-the-counter pain reliever led to the development of autism spectrum disorder and attention deficit hyperactivity disorder in children.  Since all fifty states require medical causation expert opinions as a perquisite to trial in medical issue cases, once the court excluded all of plaintiffs’ experts, it put plaintiffs on a short timeline to show cause why summary judgment should not be granted across the board.  Plaintiffs argued that they could establish general causation by cobbling together a few prior statements by one of defendants’ experts who had repeatedly testified to just the opposite.  Id. at *2. 

Defendants’ expert is a world-renowned expert on ADHD whose expert opinion was that “there is no reliable scientific evidence that maternal use of acetaminophen causes ADHD in offspring.”  Id. at *4.  And none of his “prior statements,” contradict that conclusion that he reached using the Bradford Hill criteria (discussed in more detail in our prior post).  The statements plaintiff tried to rely on fell into three categories.  First, statements that don’t refer to acetaminophen at all but generally to environmental risk factors for ADHD.  Id.  Second, statements that acknowledge an association between prenatal acetaminophen use and ADHD—a fact that is not in dispute.  But association is not causation.  Allowing evidence of association asks the jury to consider the “possibility of causation.”  Any such verdict would be “steeped in speculation.”  Id. Third, defendants’ expert has referred to acetaminophen as a “risk factor” for ADHD but has also explained that “risk factors” do not mean causation.   A common misunderstanding that

Highlight[s] the impropriety of inviting a jury to speculate as to whether a patchwork of [defendants’ expert’s] out-of-context statements, rather than his expert opinion to the contrary, proves general causation.    

Id. at *5.

Not only did plaintiffs mischaracterize many of defendants’ expert’s statements, they

fundamentally misunderstand[] the process by which scientists assess the issue of general causation. . . . Plaintiffs’ proposal — that a series of disparate scientific observations is adequate for a jury to find general causation — is not viable. The issue of general causation in this litigation is complex and serious. Juries are entitled to a thoughtful, reliable analysis by a qualified expert.

Id. at *6. 

That was plaintiffs’ third attempt at establishing general causation, and three times was enough for the court.  All plaintiffs’ claims were dismissed, and final judgement entered for defendants.  For an MDL that started out with a really bad preemption decision,  the course correction on general causation got us all the way home in grand style.