Loss Attribution Under U.S.S.G. § 1B1.3(a)(1)(B) Requires Substantial Evidence of a Jointly Undertaken Agreement—Foreseeability Alone Is Not Enough

I. Introduction

In United States v. Julian Lopez (11th Cir. Aug. 7, 2026) (per curiam) (unpublished), the Eleventh Circuit vacated a health care fraud sentence after concluding that the government failed to prove—by substantial, reliable evidence—that the defendant jointly undertook the broader fraudulent billing conducted by a clinic, One Medical Services.

Parties and posture. The United States prosecuted Julian Lopez and a co-defendant, Leonel Diaz Castillo. Lopez pleaded guilty (without a plea agreement) to two counts of health care fraud under 18 U.S.C. § 1347. At sentencing, the district court attributed to Lopez the full intended loss tied to One Medical’s billing: roughly $3.248 million, producing a 16-level enhancement under U.S.S.G. § 2B1.1(b)(1)(I), and imposed 30 months’ imprisonment plus nearly $1.5 million in restitution.

Core issue. Whether the district court clearly erred by treating One Medical’s $3.2 million intended loss as Lopez’s relevant conduct under U.S.S.G. § 1B1.3(a)(1)(B) without evidence that Lopez and One Medical (or its owner/operator) agreed to jointly undertake the multi-million-dollar fraud.

II. Summary of the Opinion

The Eleventh Circuit held that the government did not introduce substantial evidence that Lopez and One Medical agreed—explicitly or implicitly—to jointly undertake the clinic’s large-scale Medicare fraud. The record showed, at most, that Lopez obtained beneficiary cards knowing they would be used for fraud and that two claims (two $4,000 claims) were submitted using cards he purchased; it did not show a jointly undertaken agreement encompassing One Medical’s entire billing operation.

Because § 1B1.3(a)(1)(B) requires proof that the third party’s conduct was within the scope of the criminal activity the defendant agreed to jointly undertake, and because foreseeability cannot substitute for scope, the district court’s intended-loss finding was clearly erroneous. The court therefore vacated and remanded for resentencing.

III. Analysis

A. Precedents Cited

  • United States v. Isaacson, 752 F.3d 1291 (11th Cir. 2014) and United States v. Washington, 714 F.3d 1258 (11th Cir. 2013): These cases supply the baseline allocation of burdens at sentencing—when a defendant makes a factual objection, the government must prove the facts supporting a Guidelines enhancement by a preponderance of the evidence using “sufficient and reliable evidence.” The Lopez panel uses them to emphasize that bare inferences, ambiguous transcripts, and unmoored proffers do not satisfy the government’s evidentiary obligation.
  • United States v. Nerey, 877 F.3d 956 (11th Cir. 2017): Cited for the standard of review: factual findings in Guidelines calculations are reviewed for clear error. This frames the appellate inquiry as deferential—but not toothless.
  • Cooper v. Harris, 581 U.S. 285 (2017), United States v. Robertson, 493 F.3d 1322 (11th Cir. 2007), and Urias-Orellana v. Bondi, 607 U.S. 537 (2026): Together, these authorities explain that even under clear error review, findings must be supported by “substantial evidence” (more than a scintilla). The court leverages this trio to reject the district court’s inference of a $3.2 million jointly undertaken agreement from a thin record lacking identification of participants, timing, or linkage to One Medical.
  • United States v. Andrews, 953 F.2d 1312 (11th Cir. 1992): Reinforces the crucial limitation: relevant acts in a conspiracy are not automatically coextensive with all acts of the conspiracy; they must be within the scope of the defendant’s agreement. Lopez uses Andrews to disentangle “foreseeable” from “agreed-to.”
  • United States v. Hunter, 323 F.3d 1314 (11th Cir. 2003): Central to the panel’s framework. Hunter requires individualized findings on the scope of the defendant’s agreement and holds that foreseeability is assessed only after scope is determined. Lopez applies this sequencing to fault the district court’s apparent reliance on the notion that large losses were “foreseeable” if more cards were procured.
  • United States v. Whitman, 887 F.3d 1240 (11th Cir. 2018): Whitman supplies two key principles: (1) mere awareness of a larger scheme is insufficient to expand scope; and (2) active involvement can support an inference of agreement. The Lopez panel distinguishes Whitman because Whitman contained extensive corroborated proof of joint planning, coordination, and concealment among identifiable conspirators—none of which existed between Lopez and One Medical in this record.
  • United States v. LaFraugh, 893 F.2d 314 (11th Cir. 1990): Cited to acknowledge that defendants can, in theory, agree with unknown individuals. Lopez uses LaFraugh to clarify that the legal possibility does not relieve the government of proving that such an agreement actually existed here.
  • United States v. Brazel, 102 F.3d 1120 (11th Cir. 1997) and United States v. Beasley, 2 F.3d 1551 (11th Cir. 1993): These cases articulate the buyer-seller limitation: where one party’s purpose is merely to buy and the other’s is merely to sell, without an understanding beyond the sale, no conspiracy is shown. Lopez imports that logic into the § 1B1.3 scope analysis—without evidence of pooling resources, profit-sharing, coordinated operations, or similar indicia, the relationship cannot be inflated into a jointly undertaken enterprise.
  • United States v. Harbin, 601 F.2d 773 (5th Cir. 1979): Used by analogy to illustrate that conduct consistent with independent dealing cannot support imputation of broader conspiratorial activity absent evidence of joint undertaking.
  • United States v. Mercer, 165 F.3d 1331 (11th Cir. 1999): Reinforces the point that evidence showing “at most a buyer-seller relationship” is insufficient for conspiracy—supporting the panel’s conclusion that the government’s proof did not justify attributing One Medical’s entire loss to Lopez.

B. Legal Reasoning

1. The governing rule: scope first, then foreseeability. U.S.S.G. § 1B1.3(a)(1)(B) attributes others’ conduct to a defendant only if it was within the scope of the jointly undertaken activity, in furtherance of it, and reasonably foreseeable. The opinion stresses—via § 1B1.3, cmt. 3(B), United States v. Hunter, United States v. Isaacson, and United States v. Andrews—that foreseeability cannot expand the scope of the defendant’s agreement. “Acts of others” that fall outside the defendant’s agreed scope are not relevant conduct “even if those acts were known or reasonably foreseeable.”

2. The evidentiary gap: no substantial evidence of an agreement with One Medical. The government’s showing consisted of: (i) an agreed factual basis stating Lopez obtained beneficiary cards that One Medical used; (ii) two transcripts of video-recorded conversations with unidentified “Male Voice” speakers, with uncertain timing and uncertain linkage to One Medical; and (iii) argument that Lopez knew the cards would be used for fraudulent Medicare billing.

The panel found these materials insufficient to support the critical inference: that Lopez and One Medical (or its owner/operator) agreed to jointly undertake a $3.2 million fraud. The record did not identify Lopez’s “accomplices,” did not show any communication with One Medical or Mr. Castillo, did not show how One Medical acquired the cards (directly from Lopez or through intermediaries), and did not show coordinated planning, resource pooling, profit sharing, or operational integration.

3. Misframing the dispute: “end user” knowledge was not the real issue. The district court and the government treated Lopez’s position as requiring him to have known the “words, ‘One Medical.’” The Eleventh Circuit reframed the argument as factual: the government had not proven an agreement with One Medical at all. The court acknowledged, citing United States v. LaFraugh, that one can agree with unknown participants, but held that possibility does not substitute for proof.

4. Buyer-seller reasoning applied to § 1B1.3 scope. Drawing on United States v. Brazel, United States v. Beasley, and the Guidelines’ own example at § 1B1.3, cmt. 4(C)(vi), the court treated the facts as consistent with, at most, an arm’s-length transaction in illicit “inputs” (beneficiary numbers), not a jointly managed fraud operation. Even if Lopez’s conduct suggested a broader ambition (“a hundred or two hundred thousand bucks”), it did not link him to One Medical’s particular large-scale scheme.

C. Impact

1. Sentencing in health care fraud “supply chain” cases. The opinion signals skepticism toward attributing clinic-level billed losses to upstream actors (e.g., patient recruiters, data brokers, card purchasers) absent concrete proof of a joint undertaking with the billing entity. Mere knowledge that data will be used for fraud, or that fraud will be large, may not justify multi-million-dollar loss attribution under § 1B1.3(a)(1)(B).

2. Evidentiary discipline at sentencing. The decision underscores that the government must connect the defendant to the specific enterprise whose losses are to be imputed—through identifiable communications, corroborated roles, shared proceeds, coordinated activity, or other indicia of an implicit agreement. Ambiguous transcripts without speaker identification, timing, or organizational linkage are unlikely to constitute “substantial evidence.”

3. Reinforcing the “scope” limitation. By reiterating that foreseeability is irrelevant without a proven jointly undertaken scope, the opinion may constrain efforts to treat intended loss as a generalized function of what a defendant “should have expected” from the broader fraud ecosystem.

IV. Complex Concepts Simplified

  • “Relevant conduct” (U.S.S.G. § 1B1.3): Conduct counted in the Guidelines calculation even if not charged in the count of conviction. For jointly undertaken activity, it includes certain acts of others—but only within the defendant’s agreed scope.
  • “Jointly undertaken criminal activity”: Not the same as “the entire conspiracy” in the abstract. It is the particular criminal activity the defendant agreed to carry out with others, explicitly or implicitly.
  • Scope vs. foreseeability: Scope asks: “What did the defendant agree to do with others?” Foreseeability asks: “Given that agreed plan, what actions by others were reasonably predictable?” You cannot use foreseeability to enlarge scope.
  • “Buyer-seller relationship”: Repeated or even knowing illegal sales do not automatically prove a joint enterprise; courts look for additional features like shared profits, coordinated operations, or mutual stake in a broader scheme.
  • Standards of proof and review: The government must prove sentencing facts by a preponderance of the evidence. On appeal, factual findings are reviewed for clear error, but they still must be supported by substantial evidence.

V. Conclusion

United States v. Julian Lopez reinforces a disciplined application of U.S.S.G. § 1B1.3(a)(1)(B): large loss amounts generated by others cannot be attributed to a defendant unless the government proves, with substantial evidence, that the defendant agreed to jointly undertake the specific criminal activity that produced those losses. Awareness of a larger fraudulent marketplace—or even the foreseeability of large losses—does not substitute for proof of scope. In “upstream participant” fraud cases, the opinion heightens the practical importance of concrete evidence tying the defendant to the downstream billing entity’s operation before imposing guideline enhancements driven by that entity’s total intended loss.