United States v. Yoon

CourtCourt of Appeals for the First Circuit
DecidedFebruary 20, 2026
Docket24-1520
StatusPublished

This text of United States v. Yoon (United States v. Yoon) is published on Counsel Stack Legal Research, covering Court of Appeals for the First Circuit primary law. Counsel Stack provides free access to over 12 million legal documents including statutes, case law, regulations, and constitutions.

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

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

- 2 - 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.

- 3 - 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

- 4 - 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

- 5 - 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.

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