Ensuring Reliable Expert Testimony: The Obligation to Engage with Alternative Explanations Under Rule 702

Introduction

Faison-Williams v. United States, 24-1404 (2d Cir. Apr. 1, 2025) addresses the obligations of a district court acting as gatekeeper under Federal Rule of Evidence 702 when evaluating expert testimony on medical causation in a Federal Tort Claims Act (FTCA) suit. The plaintiff, Natasha Faison-Williams, sued the United States alleging her Veterans Affairs surgeon deviated from the standard of care in scheduling and supervising a thoracic microdiscectomy, which allegedly led to serious neurological injuries. The key issue on appeal is whether the district court abused its discretion by excluding the plaintiff’s causation expert for failing to “rule out” obvious alternative causes of her condition, thus granting summary judgment to the government.

Summary of the Judgment

The Second Circuit vacated the district court’s exclusion of the expert witness and reversed the grant of summary judgment. While the panel held that the district court had jurisdiction to decide the FTCA claim (rejecting the government’s exhaustion argument), it found that the court applied an unduly stringent standard under Rule 702. The appellate court ruled that an expert is not required to categorically eliminate every plausible alternative cause; rather, the court must meaningfully assess whether the expert has considered and explained why alternative explanations are unlikely. Because the district court concluded categorically that the expert “failed to rule out” alternatives without appreciating the non-conclusive but principled reasons the expert advanced, the exclusion was an abuse of discretion. The case was remanded for further proceedings.

Analysis

1. Precedents Cited

McNeil v. United States, 508 U.S. 106 (1993): Establishes the FTCA’s administrative exhaustion requirement.
28 U.S.C. § 2675(a): Requires claimants to present a tort claim to the appropriate federal agency before suing in court.
Johnson v. United States, 788 F.2d 845 (2d Cir. 1986): Explains the specificity required in an administrative claim to allow a reasonable investigation by the agency.
Collins v. United States, 996 F.3d 102 (2d Cir. 2021): Clarifies the level of detail necessary in FTCA presentment to satisfy jurisdictional requirements.
Fed. R. Evid. 702 and its 2000 Advisory Committee Notes: Set the standard for expert testimony, including consideration of “obvious alternative explanations.”
Amorgianos v. Nat’l R.R. Passenger Corp., 303 F.3d 256 (2d Cir. 2002): Confirms district courts’ gatekeeping role and reviews admissibility decisions for abuse of discretion.
Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999): Extends Daubert principles to all expert testimony and emphasizes reliability over qualifications alone.

2. Legal Reasoning

The court addressed two principal issues in turn:

Subject‐Matter Jurisdiction under the FTCA: The United States argued that Faison-Williams failed to exhaust her administrative remedies with respect to the theory that her surgeon negligently scheduled the surgery (as opposed to negligently performing it). The Second Circuit held that an agency investigation into the performance of the thoracic microdiscectomy would necessarily encompass the decision to schedule it. Under Johnson and Collins, the one‐page administrative claim was sufficiently specific to trigger a reasonable VA inquiry into both scheduling and performance, so jurisdiction was proper.
Rule 702 Gatekeeping and Exclusion of Expert Testimony: Rule 702 requires expert testimony to be based on reliable methods and a sound application to the facts. One recognized reliability factor is whether the expert has “adequately accounted for obvious alternative explanations.” The district court interpreted that factor to demand a categorical ruling out of every alternative cause. The Second Circuit explained that this misstates the standard: an expert need not conclusively eliminate each possibility, but must offer reasoned analysis why alternatives are unlikely. The Court examined Dr. Zonenshayn’s deposition and report—showing he addressed cervical spine disease, pre‐existing bladder dysfunction, childbirth effects, and psychological overlay—all with non‐conclusory explanations grounded in imaging, objective studies, and his clinical experience. Because the district court failed to credit those explanations, its exclusion of the testimony was manifestly erroneous.

3. Impact

This decision clarifies the proper application of Rule 702’s “obvious alternative cause” criterion in the Second Circuit:

District courts must engage with the substance of an expert’s reasoning on alternative explanations rather than demand categorical elimination.
Excluding expert testimony on the basis of reliability requires more than noting alternative theories; it requires demonstrating that the expert’s analysis is so deficient that no reasonable factfinder could rely on it.
The decision underscores that reliability challenges under Rule 702 must focus on methodology and reasoning, not merely on whether every conceivable alternative is definitively excluded.

Going forward, lower courts in this circuit will be guided to conduct a searching inquiry into experts’ analytic processes, crediting their experience and contextual explanations before deciding that testimony is unreliable.

Complex Concepts Simplified

FTCA Presentment Requirement: Before suing the United States for negligence by federal employees, a claimant must submit a simple administrative claim. If it describes what happened, the injury, and name of the federal agency, the court can usually proceed.
Rule 702 Gatekeeping: Judges screen expert testimony before trial to make sure it’s based on sound methods and is helpful to jurors. They look at an expert’s qualifications, the data relied upon, the methods used, and how those methods were applied.
Obvious Alternative Cause Test: When an expert says A caused B, the judge checks whether the expert considered other likely causes (C, D, E). The expert need not rule out every possibility, but should explain why the other theories don’t fit the facts as well.

Conclusion

Faison-Williams v. United States refines the Second Circuit’s approach to reliable expert testimony by emphasizing meaningful consideration of alternative explanations under Rule 702. It reaffirms that district courts must evaluate experts’ reasoning on causation holistically—crediting years of clinical experience and non‐conclusive but reasoned analyses—before excluding testimony as unreliable. This ruling preserves the balance between rigorous gatekeeping and fair access to expert assistance in complex medical-negligence cases.