In a statement of interest (“SOI”) that it filed today in United States ex rel. Witkin v. Medtronic, Inc., No. 11-cv-10790-IT (D. Mass.), the United States reiterated its view that it need not prove but-for causation in a False Claims Act (“FCA”) case predicated on a false certification of compliance with the anti-kickback statute (“AKS”), and that but-for causation itself can be proven in various ways.
The SOI pointed out that, in the First Circuit’s recent decision in United States v. Regeneron, 128 F.4th 324 (1st Cir. 2025), the court recognized two “pathway[s]” to proving False Claims Act liability based on violations of the anti-kickback statute. SOI at 2. First, under 42 U.S.C. § 1320a-7b(g), the plaintiff (the government or the relator) can seek to prove that false claims “result[ed] from” the kickback, in which case the plaintiff must prove but-for causation, but need not prove falsity or materiality. See Regeneron, 128 F.4th at 334 (citing Guilfoile v. Shields, 913 F.3d 178, 190 (1st Cir. 2019)). Or the plaintiff can seek to prove that the defendant falsely certified compliance with the anti-kickback statute, in which case the plaintiff must show falsity but need not prove but-for causation. See Regeneron, 128 F.4th at 332-33 (observing that “false-certification claims require no proof of causation”); see also United States ex rel. Hutcheson v. Blackstone Med., Inc., 647 F.3d 377, 392-94 (1st Cir. 2011).
Thus, in its SOI, the government reasserted that “there is no question that the false certification theory remains a viable way for the government (or a relator) to bring FCA claims predicated upon AKS violations.” SOI at 3.
The SOI further pointed out that, as the underlying district court decision had held, even under “Section 1320a-7b(g), the but-for causation standard is not an ‘insuperably difficult’ burden to meet.” SOI at 4 (quoting United States v. Regeneron Pharma., Inc., No. 20-11217-FDS, 2023 WL 6296393, at *12 (D. Mass. Sept. 27, 2023). Citing the district court decision, which the First Circuit affirmed, the government noted that “but-for causation (as all elements in a civil case) is evaluated under a preponderance standard, and the government (or a relator) can prove it in a variety of ways, including through circumstantial evidence and reasonable inferences.” SOI at 4. The government then noted that the First Circuit “has approved of plaintiffs proving but-for causation through various categories of evidence,” including “expert reports, aggregate statistical evidence, and other circumstantial evidence.” SOI at 5 (citing In re Neurontin Marketing and Sales Practices Litig., 712 F.3d 60, 68 (1st Cir. 2013)).
In other words, a plaintiff could show but-for causation with evidence that, after a physician received a kickback from a pharmaceutical company, the physician prescribed more of the company’s drug, even if the physician denied that the kickback influenced his or her prescribing behavior. Or a plaintiff might show but-for causation with evidence that the kickback recipient’s behavior (whether in terms of prescribing or other recommendations of items or services reimbursed by Federal health care programs) favored the kickback payer in a way that differed markedly from national or regional norms.