Law and science may occupy different spheres—one dealing with cases argued in courtrooms, the other with hypotheses tested in laboratories. Yet both disciplines rest on the same foundation: the pursuit of truth. Each requires evidence to be gathered systematically and presented in a uniform, transparent way.
Both also depend on gatekeepers—judges in one system, peer reviewers in the other—to ensure that conclusions are supported by reliable facts rather than speculation.
Right now, the Second Circuit in New York is deciding whether federal courts will continue to enforce these standards for expert testimony or allow speculative, methodologically weak studies to reach a jury.
Under Rule 702 of the Federal Rules of Evidence, courts must ensure that expert testimony presented to a jury is grounded in sufficient data, reliable methods, and a sound application of those methods to the facts of a case. The rule makes the judge a gatekeeper, responsible for preventing unreliable opinions—offered under the guise of expertise—from reaching a jury.
In August 2024, U.S. District Judge Denise Cote fulfilled exactly that duty.
She dismissed lawsuits alleging that prenatal use of acetaminophen, the active ingredient in Tylenol, causes neurodevelopmental disorders. Her decision followed a close review of the plaintiffs’ experts, whose methodologies were selective, inconsistent, and insufficiently rigorous. In other words: pseudoscience.
Judge Cote correctly concluded that the experts failed to meet Rule 702’s reliability requirements. In particular, she found they relied heavily on observational studies without adequately addressing major confounding factors—including genetic influences that many researchers identify as central to ADHD and related diagnoses.
The plaintiffs’ experts also failed to sufficiently acknowledge the numerous studies that undercut their claims. Recognizing and addressing contradictory findings—such as new research published in The Lancet and conclusions reached by the American College of Obstetricians and Gynecologists—is essential to both scientific credibility and courtroom admissibility.
Cote also identified what appellate courts have long described as an “analytical gap”—a disconnect between the data in the literature and the causal conclusions the experts advanced. Many of the underlying studies expressly cautioned against drawing causal inferences. Yet the plaintiffs’ experts took the extra step and argued for causation.
Rule 702 does not permit experts to bridge such gaps.
Now the Second Circuit Court of Appeals is reviewing Cote’s decision. The question before it is not whether acetaminophen is safe, nor whether scientific inquiry into neurodevelopmental disorders should continue. The question is narrower: Did the district court properly perform its gatekeeping role?
The answer must be yes.
Reversing Judge Cote’s ruling would do more than revive a single set of lawsuits. It would signal that methodological rigor is optional, that selective readings of data are sufficient, and that courts should defer evidentiary questions to juries even when foundational reliability is lacking. That approach would erode the very purpose of judicial gatekeeping.
If appellate courts weaken those standards, the effects will extend far beyond this case.
Future litigants would be incentivized to produce litigation-driven research designed to survive just long enough to reach a jury. Experts could aggregate distinct medical conditions into sweeping theories untethered to specific allegations—just as the plaintiffs’ experts did with autism and ADHD.
Known confounders, like genetics, could be minimized rather than rigorously addressed. Regulatory consensus could be brushed aside without serious engagement.
The result would be predictable: more pressure on companies to settle meritless claims to avoid the uncertainty of jury trials, and a legal system increasingly unable to distinguish between hypothesis and proof.
The judiciary’s gatekeeping function exists precisely to prevent that kind of backsliding. When courts insist that expert testimony reflects disciplined methodology and faithful engagement with the full body of evidence, they protect not only defendants, but juries—and the integrity of the legal system itself.
