United States v. Yoon

Court of Appeals for the First Circuit·Decided February 20, 2026·No. 24-1520·Published

Opinion

United States Court of Appeals For the First Circuit

No. 24-1520 UNITED STATES OF AMERICA, Appellee,

v.

CHANG GOO YOON,

Defendant, Appellant.

APPEAL FROM THE UNITED STATES DISTRICT COURT FOR THE DISTRICT OF MASSACHUSETTS

[Hon. Indira Talwani, U.S. District Judge]

Before

Barron, Chief Judge,

Rikelman and Aframe, Circuit Judges.

Leigh Ann Webster, with whom Strickland Webster, LLC was on brief, for appellant.

Karen L. Eisenstadt, Assistant United States Attorney, with whom Leah B. Foley, United States Attorney, was on brief, for appellee.

February 20, 2026

AFRAME, Circuit Judge. Over four years, Chang Goo Yoon submitted more than a million dollars in false health insurance claims, resulting in his conviction on two counts of health care fraud under 18 U.S.C. § 1347. He now appeals certain evidentiary rulings and the application of two enhancements under the sentencing guidelines. We affirm.

I. Offense Conduct

Because Yoon's appeal challenges evidentiary rulings, we provide a balanced summary of the trial evidence. United States v. Villa-Guillen, 102 F.4th 508, 512-13 (1st Cir. 2024).

Yoon worked as a licensed physical therapist who owned and operated several clinics in Massachusetts. Between November 2014 and November 2018, Yoon submitted numerous claims to private health insurers, including Blue Cross Blue Shield ("Blue Cross") and Aetna, for services he never rendered. Yoon often billed for services that he supposedly provided while either he or the patient he claimed to treat was out of town. Yoon also created false treatment notes under another provider's name and used those notes to submit personal injury claims to his own car insurer, MAPFRE, for never-performed physical therapy sessions.

To effectuate his scheme, Yoon submitted claims that listed his office address as his patients' addresses so that reimbursement checks went directly to him. Doing so avoided

situations in which patients might become suspicious after receiving paperwork for services never rendered.

Eventually, Yoon's false billing caught up with him. A jury convicted him on two counts of health care fraud. Count One addressed the fraud against Blue Cross and Aetna; Count Two addressed the fraud against MAPFRE.1

II. Evidentiary Challenges A.

Before trial, Yoon moved to exclude several pieces of evidence, two of which are relevant here. First, he sought to exclude "evidence regarding any investigation or adverse action by any private insurance companies" against him. Yoon was especially concerned about a 2015 investigation by Blue Cross into his billing practices. Based on the findings of its investigation, Blue Cross required Yoon to provide proof that he rendered the services in question before receiving any subsequent reimbursements. Yoon opposed the admission of evidence related to that investigation, including letters that Blue Cross sent to him.

Second, Yoon sought to exclude evidence regarding a 2007 investigation by Colorado authorities into his billing practices. Yoon had been licensed as a physical therapist in Colorado prior

1 Yoon's appeal does not concern Count Two, so we do not discuss it further.

to the conduct at issue in this case. But after an allegation of misconduct by the Colorado licensure board regarding his billing practices, Yoon entered an agreement to suspend his license there. At trial, Yoon sought to keep out any reference to that investigation and its outcome.

The parties addressed this disputed evidence during two pre-trial conferences. At the first conference, the district court permitted the government to introduce evidence of Yoon's knowledge about the insurance company investigations; however, it did not allow the government to introduce the results of those investigations. The court reserved ruling on the admissibility of the Colorado investigation until Yoon provided more information about his defense strategy.

At the second conference, Yoon explained that he planned to argue he lacked a knowing and willful mental state, which is required for conviction of health care fraud under § 1347, see United States v. Troisi, 849 F.3d 490, 494 & n.8 (1st Cir. 2017), and instead submitted the false bills negligently because he was overworked and disorganized. Given that defense, the district court allowed the government to submit evidence of the Colorado investigation but again limited the evidence to Yoon's awareness of the investigation.

Finally, the parties discussed how the government would introduce evidence of the investigations. Most of the discussion

concerned an August 2015 letter sent from a Blue Cross fraud investigator, Martin Flood, notifying Yoon of the Blue Cross investigation; a 2018 letter from Flood to Yoon's then-attorney, Jonathan Plaut, explaining that Yoon had been placed on "pre-payment review," meaning Yoon had to submit proof that he rendered services before receiving reimbursements; and Plaut's response to Flood's 2018 letter. The district court decided to admit these letters, but required substantial redactions, including to parts of the letters stating that Flood was from the "fraud and prevention" unit. Still, the parties agreed that Flood could testify to his responsibilities at Blue Cross.

The parties also discussed how the government would introduce the evidence about the Colorado investigation. Ultimately, the district court allowed the government to ask a witness two yes-or-no questions about whether Yoon had ever acknowledged that his billing practices had been investigated by Colorado authorities.

At trial, the government called several witnesses, including Donna Dziedzic-Bianco, an investigator at Aetna, and Flood (together, "the investigators"). They testified about the billing rules and procedures of their respective employers. For example, they detailed the types of information that providers would include in claims and explained that providers could not submit claims for services rendered to family members. The

investigators also testified that some of Yoon's claims contained atypical or even unique patterns, such as claims with identical patient and clinic addresses and claims requesting that payment be sent to the clinic address.

Through Flood's testimony, the government also introduced the letters about the Blue Cross investigation. Flood explained that following the 2015 letter announcing the investigation, Yoon brought boxes of documents to a Blue Cross office and sat for an interview. Before Flood discussed the 2018 letters between Blue Cross and Yoon's attorney, the district court instructed the jury to consider the letters only insofar as they pertained to Yoon's knowledge and intent; it expressly told the jury not to consider the letters for their truth.

The government also called several of Yoon's employees.

One testified that Yoon told her that Colorado authorities had investigated him. She also detailed how Yoon tracked his patients' insurance plans, explaining that Yoon described some policies as "pretty good" when they covered more of a claim. Another employee also noted Yoon's attention to billing, explaining that Yoon discouraged her from spending too much time with patients who had low reimbursement rates, and that Yoon once mentioned "insurance, [and] how much [insurers] pay based on their [billing] code."

B.

On appeal, Yoon asserts two evidentiary challenges. He argues that the district court should have excluded (1) the evidence related to the Blue Cross and Colorado investigations, and (2) the investigators' testimony. We review preserved evidentiary challenges for abuse of discretion and unpreserved challenges for plain error. See Alaniz v. Bay Promo, LLC, 143 F.4th 18, 29 (1st Cir. 2025). The parties dispute the applicable standard. Because Yoon's arguments fail under the more defendant-friendly abuse-of-discretion standard, we assume that Yoon preserved his claims unless otherwise noted. See id.

1.

Free access — add to your briefcase to read the full text and ask questions with AI

United States v. Yoon, (1st Cir. 2026).

United States v. Yoon (United States v. Yoon) — published by Counsel Stack Legal Research, free access to 12M+ legal documents.

Related

United States v. Garrison
133 F.3d 831 (Eleventh Circuit, 1998)
United States v. Williams
527 F.3d 1235 (Eleventh Circuit, 2008)
United States v. Cassell, Dwayne
292 F.3d 788 (D.C. Circuit, 2002)
United States v. Wilkerson
251 F.3d 273 (First Circuit, 2001)
United States v. Nelson-Rodriguez
319 F.3d 12 (First Circuit, 2003)
United States v. Landrau-Lopez
444 F.3d 19 (First Circuit, 2006)
United States v. Maher
454 F.3d 13 (First Circuit, 2006)
United States v. Sicher
576 F.3d 64 (First Circuit, 2009)
United States v. Enitan Isiwele
635 F.3d 196 (Fifth Circuit, 2011)
United States v. John Christo, Jr.
614 F.2d 486 (Fifth Circuit, 1980)
United States v. Jeffrey Jay Rutgard
116 F.3d 1270 (Ninth Circuit, 1997)
United States v. Nokuzola Ntshona
156 F.3d 318 (Second Circuit, 1998)
United States v. Henry Miles Sherman
160 F.3d 967 (Third Circuit, 1998)
United States v. Carol Hoogenboom
209 F.3d 665 (Seventh Circuit, 2000)
United States v. Martin Geevers
226 F.3d 186 (Third Circuit, 2000)
United States v. Joseph Lonnie Hodge
259 F.3d 549 (Sixth Circuit, 2001)
United States v. Robert B. Miller
316 F.3d 495 (Fourth Circuit, 2003)
United States v. August L. Holthaus, Jr.
486 F.3d 451 (Eighth Circuit, 2007)