What's the Test for Causation in a False Claims Act Suit Based Upon the Anti-Kickback Act?

This is an issue only a lawyer could love, but there's already a circuit split, and two federal judges in the Massachusetts District have reached opposite conclusions, with one of them asking for a resolution by the First Circuit, which will either deepen the split or (if it comes up with a third approach) broaden it. Considering the large number of qui tam actions for AKB violations that are litigated each year, this is an important issue that cries out for resolution by SCOTUS. 

How much do lawyers love this issue? Here is a collection of law firms' commentary on the issue in the last couple of months --

• Haynes and Boone, Another Win for Defendants on the Issue of Causation in AKS-Based FCA Cases (Oct. 5) (extensive analysis)
• Sidley: District of Massachusetts Adopts But-For Causation Test for FCA Claims Premised on AKS Violations (Oct. 3)
• WilmerHale: Government Setback “Resulting From” Another Court Adopting the “But For” Causation Standard for False Claims Act Cases Furthering Court Split (Oct. 19)
• DLA Piper: Massachusetts District Judge rules that government must clear high causation bar in False Claims Act cases (Oct. 10)
• ArentFox: Federal Judge Rules Government Must Demonstrate “But-For” Causation for Anti-Kickback Statute Claims (Oct. 6)
• Goodwin Procter: “Greenfield Fraught with Problems”: District of Massachusetts Holds But-For Causation Required in False Claims Act Cases Based on Kickbacks (Oct. 5)
• Bradley: District of Massachusetts Split on Causation Standard in Kickback FCA Cases (Oct. 30)
• Mintz: Courts Continue to Grapple with the Causation Standard for False Claims Act Suits Based on Alleged Kickback Schemes, While the Supreme Court Stays on the Sidelines (Oct. 5)
• Squire Patton Boggs: Federal Courts Continue to Grapple with Causation in Anti-Kickback-Based False Claims Act Cases (Nov. 29)
• Bass Berry & Sims: District Courts Wrestle with Causation in Kickback Cases While Circuit Courts Remain Divided (Oct. 5)
• Weiner Brodsky Kider: Mass. Federal Court Adopts More-Stringent Causation Standard for FCA Claims Based on Alleged Unlawful Kickbacks (Oct. 12)
• McGuireWoods: The Growing Causal Divide: But-For Causation in AKS/FCA Actions (Dec. 4) (citations and some hyperlinks to opinions)
• Akerman: Teva FCA Decision Sheds Light on Varying Interpretations of the Elements of an FCA Claim (Aug. 10)
• Hogan Lovells: Anti-kickback causation in FCA suits: text or purpose? (undated, but apparently written before the D. Mass. split)
• Ropes & Gray: Sixth Circuit Requires But-For Causation and Narrowly Defines Remuneration under AKS (April 4) (before the D. Mass. split)
• Arnold & Porter: More Disagreement About the Causation Standard for AKS Cases Under the FCA (July 21) (before the Regeneron case created a split within the Mass. District)

For a very brief introduction to the laws involved in this split, you can start with the HHS OIG website.