                               RECOMMENDED FOR FULL-TEXT PUBLICATION
                                   Pursuant to Sixth Circuit I.O.P. 32.1(b)
                                             File Name: 15a0185p.06

                       UNITED STATES COURT OF APPEALS
                                        FOR THE SIXTH CIRCUIT
                                          _________________


 UNITED STATES OF AMERICA,                                        ┐
                                         Plaintiff-Appellee,      │
                                                                  │
                                                                  │        No. 12-3212
            v.                                                    │
                                                                   >
                                                                  │
 PAUL H. VOLKMAN,                                                 │
                                     Defendant-Appellant.         │
                                                                  ┘
                             Appeal from the United States District Court
                            for the Southern District of Ohio at Cincinnati.
                        No. 1:07-cr-60-3—Sandra S. Beckwith, District Judge.
                                   Decided and Filed: August 14, 2015

         Before: McKEAGUE and DONALD, Circuit Judges; LAWSON, District Judge.*

                                            _________________

                                                  COUNSEL

ON BRIEF: Edwin A. Perry, FEDERAL PUBLIC DEFENDER’S OFFICE, Memphis,
Tennessee, for Appellant. Kimberly R. Robinson, UNITED STATES ATTORNEY’S OFFICE,
Columbus, Ohio, for Appellee. Paul H. Volkman, Terre Haute, Indiana, pro se.

                                            _________________

                                                  OPINION
                                            _________________

        BERNICE BOUIE DONALD, Circuit Judge. When a doctor first enters the practice of
medicine, he or she swears to abide by a prime directive of the profession: “First, do no harm.”
Paul Volkman breached this sacrosanct tenet when he prescribed narcotics to addicts and


        *
         The Honorable David M. Lawson, United States District Judge for the Eastern District of Michigan, sitting
by designation.




                                                        1
No. 12-3212                             United States v. Volkman                           Page 2

individuals with physical, mental, and psychological frailties.                 A federal jury looked at
Volkman’s actions and found him guilty of breaking several laws, chief among them the law
prohibiting the unlawful distribution of controlled substances. After receiving the jury’s verdict,
the district court sentenced Volkman to four consecutive terms of life imprisonment, to be served
concurrently with a number of less-lengthy terms.

        Volkman appealed his conviction and sentence and we affirmed the district court by
published opinion. See United States v. Volkman, 736 F.3d 1013 (6th Cir. 2013). The Supreme
Court then granted Volkman a writ of certiorari and vacated our judgment. See United States v.
Volkman, 135 S. Ct. 13 (2014). On remand, we are asked to consider, in light of Burrage v.
United States, 134 S. Ct. 881 (2014), whether sufficient evidence of but-for causation supported
Volkman’s convictions under the Controlled Substances Act. Because we find the evidence of
but-for causation sufficient and because Volkman’s other allegations of error continue to lack
merit, we AFFIRM the district court and resubmit this opinion, amended at Section IV.C, to
address Burrage’s but-for standard of causation.

                                                       I.

        Paul Volkman is a former doctor who cast himself as a “pain management physician.”
Educated at the University of Chicago, Volkman holds an M.D. and Ph.D. in pharmacology from
that institution. See Volkman v. United States Drug Enforcement Admin., 567 F.3d 215, 217 (6th
Cir. 2009). Before the events leading up to his conviction, he was board-certified in emergency
medicine and was a “diplomat” of the American Academy of Pain Management.

        Despite his professional pedigree, Volkman fell into hard times in 2003. He had been
sued on several occasions, settling some cases and losing others. Id. By the time his legal woes
were over, he had no malpractice insurance and no job.

        As part of his effort to rectify the latter, Volkman called Denise Huffman at the Tri-State
Health Care clinic, asking about job opportunities. Eventually, Denise1 hired him to provide the



        1
         To minimize confusion, we will refer to Denise Huffman and her daughter, Alice Huffman Ball, by their
given names.
No. 12-3212                         United States v. Volkman                       Page 3

clinic’s medical services. They agreed that Volkman’s salary would be $5,000 per week—
eventually, the amount was upped to $5,500 per week.

       Tri-State operated as a cash-only clinic. Pain medication was its bread and butter. At its
peak, Tri-State and its staff saw an average of eighteen to twenty patients a day.

       Volkman worked without incident during his first few months at the clinic.                 But
approximately six months into the job, his practice encountered a major hiccup—local
pharmacies refused to fill the clinic’s prescriptions, citing concerns of improper dosing.
Volkman’s solution? Open a dispensary in the clinic. Volkman asked Denise’s daughter, Alice
Huffman Ball, to research the process for obtaining a license to operate a dispensary. Denise
objected and raised concerns, but Volkman assured her that “he was a doctor[,] so he could
dispense his own medication and he could take care of everything.”

       Volkman submitted to the Ohio Board of Pharmacy an application for a license to
distribute controlled substances. Board representatives conducted an inspection of the clinic
grounds, during the course of which they found a Glock in the safe where the drugs were stored.
Despite this discovery, the Board issued a license after its initial inspection.

       Agents from the Board conducted a follow-up inspection in December 2003. This time,
they saw several problems with the new dispensary’s practices. For instance, the dispensary logs
were sloppily maintained; Volkman provided little oversight over recordkeeping processes. No
licensed physician or pharmacist oversaw the actual dispensing process.              Patients returned
unmarked and intermixed medication.

       By February 2004, the clinic took adequate measures to ameliorate the Board’s
administrative concerns. But the clinic still had its problems. Volkman was in charge of the
dispensary, but did a poor job of regulating access—the drug safe’s security was porous, with
unauthorized personnel regularly accessing the pharmaceutical stockpile contained inside.
Despite these issues, the dispensary saw much activity—it purchased 135,900 dosage units of
oxycodone between July and December 2003, 457,100 dosage units for the entirety of 2004, and
414,200 dosage units between January and September 2005.
No. 12-3212                        United States v. Volkman                     Page 4

       It eventually became clear that Volkman’s medical practice followed a questionable
pattern. Drug addicts, drug peddlers, or individuals otherwise not complaining of pain would
come to see him as his “patients.” Very little was done in terms of taking medical histories or
conducting physical examinations.       Volkman would regularly prescribe a drug cocktail
consisting of opiates (such as oxycodone and hydrocone) as well as sedatives (diazepam,
alprazolam, and carisoprodol; more commonly referred to as Valium, Xanax, and Soma). He
had a tendency of first resorting to narcotics, disregarding first lines of treatment for pain
management such as non-steroidal anti-inflammatory drugs (NSAIDs).

       A federal investigation of Tri-State led to a search of the clinic facility on June 7, 2005.
Medical personnel accompanying the investigative team saw that the clinic was in utter disarray.
Urine specimen cups, filled with urine, were scattered all over the floor. The clinic had no
equipment to view X-rays and MRI results. Miscellaneous pills were strewn all throughout the
clinic premises.

       Three months after the investigation, Denise terminated Volkman’s employment because
she “could no longer get along with him” and because there was “no control.” In her words, “Dr.
Volkman did what Dr. Volkman wanted to do.” Volkman decided to open his own shop in
Ohio—first in Portsmouth, and later in Chillicothe.

       Twelve of Volkman’s patients died during his tenure at Tri-State and during the early
months of his new practice. Kristi Ross, Steve Hieneman, Bryan Brigner, and Earnest Ratcliff
were four of these patients.

       A grand jury returned an indictment against Volkman, Denise, and Alice, charging them
with one count of conspiring to unlawfully distribute a controlled substance in violation of 21
U.S.C. § 841(a)(1) (the Controlled Substances Act or “CSA”), two counts of maintaining a drug-
involved premises in violation of 21 U.S.C. § 856(a)(1), eight counts of unlawful distribution of
a controlled substance leading to death in violation of 21 U.S.C. §§ 841(a)(1) and 841(b)(1)(C),
and four counts of possession of a firearm in furtherance of a drug-trafficking crime in violation
of 18 U.S.C. §§ 924(c)(1) and (2). Volkman was charged separately with five additional counts
of unlawful distribution of a controlled substance leading to death, as well as two additional
No. 12-3212                        United States v. Volkman                     Page 5

counts of maintaining a drug-involved premises. His co-defendants, Denise and Alice, entered
into plea agreements with the Government and testified against their former colleague.

       After a thirty-five-day trial, a jury convicted Volkman on the lone conspiracy count,
seven counts of unlawful distribution that did not lead to death, four counts of unlawful
distribution leading to death, four counts of maintaining a drug-involved premises, and one count
of possessing a firearm in furtherance of a drug-trafficking offense. The jury acquitted him on
one count of unlawful distribution, as well as one count of possessing a firearm in furtherance of
a drug-trafficking offense.

       The district court sentenced Volkman to four consecutive terms of life imprisonment for
the counts of unlawful distribution leading to death, to be served concurrently with a sentence of
240 months for the counts of conspiracy and unlawful distribution not leading to death,
120 months for the drug-related premises counts, and 60 months for the firearm count, followed
by three years of supervised release. Volkman timely appealed.

                                                II.

       Volkman divides his argument into four parts. He first argues that the district court erred
by denying a proposed jury instruction derived from the Supreme Court’s decision in Gonzales v.
Oregon, 546 U.S. 243 (2006).       Next, he contends that the Government’s expert witnesses
improperly provided legal conclusions as to whether Volkman’s actions had a “legitimate
medical purpose.” Third, he claims that there was insufficient evidence to support the jury’s
guilty verdict on several charges. Finally, he challenges the reasonableness of his sentence on
numerous grounds.

       First, we turn to Volkman’s jury-instruction argument. We review a denial of a proposed
jury instruction for an abuse of discretion. United States v. Theunick, 651 F.3d 578, 589 (6th Cir.
2011). Under this standard of review, we may reverse a district court’s denial only if the
proposed instruction “is (1) a correct statement of the law, (2) not substantially covered by the
charge actually delivered to the jury, and (3) concerns a point so important in the trial that the
failure to give it substantially impairs the defendant’s defense.” United States v. Franklin,
415 F.3d 537, 553 (6th Cir. 2005) (citation and quotation marks omitted).
No. 12-3212                         United States v. Volkman                       Page 6

        Volkman sought to have the following language included in the jury charge: “In other
words, in order to find the defendant guilty, you must find that he used his prescription-writing
power as a means to engage in the illicit drug-dealing and trafficking as conventionally
understood.” As we previously noted above, this language comes directly from the Supreme
Court’s decision in Gonzales. See 546 U.S. at 269-70. Accordingly, Volkman contends that the
proposed language—copied verbatim from Gonzales—reflected a correct statement of the law
that should have been included in the district court’s instructions to the jury.

        Verbatim, however, does not necessarily mean correct. Context is critical, and in the
present context of federal criminal law, Gonzales provides us with little guidance.

        We join our sister circuits in making this observation. In United States v. Lovern,
590 F.3d 1095 (10th Cir. 2009), the Tenth Circuit commented on Gonzales’ relevance—or lack
thereof—in the setting of a criminal prosecution. The court explained that Gonzales dealt only
with the question of the Attorney General’s ability to define “legitimate medical purpose” in
light of state medical standards to the contrary. See id. at 1100. Gonzales was decided in the
setting of administrative law, not criminal law. In the court’s view, Gonzales was not relevant to
the criminal prosecution at issue in Lovern because there was “no interpretive rule seeking to
define a practice as lacking any legitimate medical purpose, let alone a rule that conflict[ed] with
a state’s assessment of the legitimacy of that practice.” Id. Instead, the Lovern court noted that
the Government properly sought to prove the lack of a legitimate medical purpose by evidentiary
means, leaving the question of what constitutes “the usual course of professional practice” for a
jury to sort out. See id.

        The Eighth Circuit made similar observations in United States v. Kanner, 603 F.3d 530
(8th Cir. 2010), where it adopted and expanded upon the Tenth Circuit’s reasoning. There, a
defendant argued that the indictment should have included the same language from Gonzales that
Volkman relies upon now. Id. at 533. The Kanner court rejected the defendant’s argument by
quoting the Lovern decision. Id. at 533-34. It added to the Lovern court’s conclusions by noting
that “Gonzales did not supplant the standard for violations of the CSA.” Id. at 535. “Rather,
post-Gonzales, knowingly distributing prescriptions outside the course of professional practice is
a sufficient condition to convict a defendant under the criminal statutes relating to controlled
No. 12-3212                          United States v. Volkman                  Page 7

substances.” Id. (quoting United States v. Armstrong, 550 F.3d 382, 397 (5th Cir. 2008), cert.
denied, 130 S. Ct. 54 (2009)).

        As our sister circuits have suggested, Gonzales did not impose new requirements to prove
a violation of the CSA. Instead, the statement that Volkman now quotes was merely part of the
Court’s commentary about statutory intent, federalism, and rulemaking authority—none of
which is at issue here. See Gonzales, 546 U.S. at 270.

        In the past, we have endorsed a broad approach to determining what conduct falls outside
the accepted bounds of professional practice so as to constitute a CSA violation, eschewing a
preestablished list of prohibited acts in favor of a case-by-case approach. See United States v.
Kirk, 584 F.2d 773, 784 (6th Cir. 1978). Simply put, Volkman’s proposed instruction would
have needlessly narrowed the scope of the jury’s inquiry to a question of whether Volkman
engaged in “conventional” drug dealing and trafficking by using his prescription power. By
narrowing the scope of the jury’s deliberation in such a manner, Volkman’s instruction would
have been inconsistent with our endorsement of the broad approach, improperly cabining a
decision that is properly left to the jury.

        Moreover, the district court raised fair questions about the nebulousness of the proposed
instruction.   What does it mean for drug dealing and trafficking to be “conventionally
understood”?     If Volkman’s goal was to conjure up the unsavory specter of “street” drug
dealing—complete with imagery of shady characters conducting quick, suspicious handoffs—
then his instruction was not an accurate statement of the law, for “street” drug dealing is not
necessary to prove a violation of the CSA. It is not difficult to see, however, how a lay juror
might think that proof of such “street dealing” was necessary for conviction under Volkman’s
proposed standard. In that respect, we agree with the district court that the instruction would
have “muddied the waters,” thereby providing an inaccurate statement of the law.

        Gonzales did nothing to alter the reality that “‘knowingly distributing prescriptions
outside the course of professional practice is a sufficient condition to convict a defendant under
the criminal statutes relating to controlled substances.’” Kanner, 603 F.3d at 535 (quoting
Armstrong, 550 F.3d at 397). Volkman’s proposed jury instruction improperly would have
No. 12-3212                         United States v. Volkman                       Page 8

cabined the scope of what the jury could consider, thereby providing an inaccurate statement of
law. Therefore, the district court correctly denied Volkman’s request.

       Our decision to uphold the district court’s denial is reinforced by the second prong of our
review: whether the jury charge issued by the district court substantially covered what Volkman
sought to convey by his proposed instruction. We conclude that the jury charge was not only
adequate, but an example of model instructions for cases such as this one.

       After reviewing the elements of a § 841(a)(1) offense and the meaning of certain terms
such as “distribute,” “dispense,” and “practitioner,” the district court provided a lay explanation
of the contours of the crime. It stated:

               No one can avoid responsibility for a crime by deliberately ignoring the
       obvious. If you are convinced that the defendant deliberately ignored a high
       probability that the controlled substances as alleged in these counts were
       distributed or dispensed outside of the course of the professional practice and not
       for a legitimate medical purpose, then you may find that the defendant knew that
       this was the case.

(DE 482, PageID 8588-89.) Next, the court elaborated on the burden of proof:

               But you must be convinced beyond a reasonable doubt that the defendant
       was aware of a high probability that the controlled substances were distributed or
       dispensed outside the course of professional practice and not for a legitimate
       medical purpose, and that the defendant deliberately closed his eyes to what was
       obvious. Carelessness or negligence or foolishness on his part are not the same as
       knowledge and are not enough to find him guilty on any of these counts. This of
       course is all for you to decide.

(DE 482, PageID 8589.)          After explaining the textbook definition of “usual course of
professional practice,” the trial court connected the definition to the instant case:

       A physician’s own individual treatment methods do not, by themselves, establish
       what constitutes a “usual course of professional practice.” In making medical
       judgments concerning the appropriate treatment for an individual, however,
       physicians have discretion to choose among a wide range of available options.
              It’s the theory of the defense that the Doctor Volkman, Doctor Paul H.
       Volkman, treated his patients in good faith. If a physician dispenses a drug in
       good faith in the course of medically treating a patient, then the doctor has
       dispensed the drug for a legitimate medical purpose in the usual course of
       accepted medical practice. That is, he has dispensed the drug lawfully.
No. 12-3212                        United States v. Volkman                     Page 9

              “Good faith” in this context means good intentions and an honest exercise
       of professional judgment as to a patient’s medical needs. It means that the
       defendant acted in accordance with what he reasonably believed to be proper
       medical practice.
              In considering whether the defendant acted with a legitimate medical
       purpose in the course of usual professional practice, you should consider all of the
       defendant’s actions and the circumstances surrounding them.
       ...
               The defendant does not have to prove to you that he acted in good faith;
       rather, the burden of proof is on the government to prove to you beyond a
       reasonable doubt that the defendant acted without a legitimate medical purpose
       outside the course of usual professional practice.

(DE 482, PageID 8589-90 (emphasis added).) The court capped off its explanation with a
discussion about the standard of care:

               You’ve heard the phrase “standard of care” used during the trial by several
       witnesses. When you go to see a doctor as a patient, the doctor must treat you in a
       manner that meets the applicable standard of care that physicians of similar
       training would have given to you under the same circumstances. If a doctor fails
       to provide you with that care, the doctor may be found neglect [sic] in a civil
       lawsuit.
               This case is not about whether the defendant acted negligently or whether
       he committed malpractice. Rather, in order for you to find the defendant guilty,
       you must find that the government has proved to you beyond a reasonable doubt
       that the defendant’s action was not for a legitimate medical purpose in the usual
       course of professional practice.

(DE 482, PageID 8590-91.)

       We conclude that these instructions amply and accurately conveyed the meaning of
“legitimate medical purpose” to the jury—the ultimate purpose of Volkman’s proposed
instruction. Not only were these instructions adequate to allay Volkman’s concerns, they served
as a model of clarity and comprehensiveness in defining the unlawful-distribution offense for a
case involving a so-called “pill mill” doctor. The district court’s instructions appropriately
defined the contours of the offense without unduly cabining the jury’s ability to consider a broad
swath of evidence in determining whether Volkman’s conduct had no legitimate medical
purpose. See United States v. August, 984 F.2d 705, 713 (6th Cir. 1992) (“There are no specific
guidelines concerning what is required to support a conclusion that an accused acted outside the
No. 12-3212                        United States v. Volkman                   Page 10

usual course of professional practice.”). Hence, the district court properly rejected Volkman’s
proposed instruction.

                                               III.

       Next, we address Volkman’s argument that the district court improperly admitted expert
testimony containing a legal conclusion. We review a district court’s admission of expert
testimony for an abuse of discretion. In re Scrap Metal Antitrust Litig., 527 F.3d 517, 528 (6th
Cir. 2008). The evidentiary admission must be upheld unless the district court “base[d] its ruling
on an erroneous view of the law or a clearly erroneous assessment of the evidence.” Best v.
Lowe’s Home Ctrs., Inc., 563 F.3d 171, 176 (6th Cir. 2009) (quotation omitted).

       We accord district courts a “wide, but not unlimited, degree of discretion in admitting or
excluding testimony [that] arguably contains a legal conclusion.”       United States v. Nixon,
694 F.3d 623, 631 (6th Cir. 2012) (quoting Torres v. Cnty. of Oakland, 758 F.2d 147, 150 (6th
Cir. 1985)) (internal quotation marks omitted). A witness’ testimony contains a legal conclusion
only if “the terms used by the witness have a separate, distinct and specialized meaning in the
law different from that present in the vernacular.” Torres, 758 F.2d at 151. An expert may not
opine on the overarching question of guilt or innocence, but he or she may “stat[e] opinions that
suggest the answer to the ultimate issue or that give the jury all the information from which it
can draw inferences as to the ultimate issue.” Berry v. City of Detroit, 25 F.3d 1342, 1353 (6th
Cir. 1994).

       Here, the controverted expert testimony followed a pattern. First, the Government would
ask its expert witnesses about Volkman’s history with a particular patient. After some back-and-
forth about a patient’s condition and the prescriptions Volkman dispensed, the Government
would ask the expert whether he or she had an opinion as to whether the prescriptions fell within
the scope of legitimate medical practice. The answer was typically no. Consider, for example,
this exchange between the prosecution and Dr. Douglas Kennedy:

       Q.      Doctor, do you have an opinion as to whether or not the prescriptions
       received from Dr. Volkman by Mr. Ratcliff back on October 21, 2005 were
       written within the scope of legitimate medical practice?
No. 12-3212                        United States v. Volkman                    Page 11

       A.      Absolutely not. They were not written for any legitimate medical purpose.

Volkman asserts that this type of testimony constituted an improper legal conclusion.

       We disagree, and join at least two of our sister circuits in doing so. The Seventh Circuit’s
decision in United States v. Chube II, 538 F.3d 693 (7th Cir. 2008), is particularly persuasive.
There, two doctors were convicted of unlawfully distributing controlled substances.            The
Government introduced testimony by experts who concluded that the doctors’ prescription
practices did not conform to the “usual standards of medical practice” and were devoid of a
“legitimate medical purpose.” Id. at 697. A typical colloquy between the Government and an
expert went something like this:

       Q. [by the prosecution]: Doctor, would you like me to repeat the question?
       THE WITNESS: I believe I recall it pretty well . . . . It is never appropriate to
       write a prescription for the spouse of a patient when that prescription is intended
       for the patient; even more so when it’s a Schedule II narcotic . . . . It’s not
       consistent with the usual course of medical practice.
       Q. And that would not be for a legitimate medical purpose, correct?

       A. Correct.

Id. at 698. The court explained that “what the jury heard was . . . an opinion from the expert that
no legitimate medical purpose existed for the prescription in question.” Id. (emphasis added). It
concluded that the district court did not abuse its discretion in allowing such testimony. Id. at
699. The Seventh Circuit was motivated by a practical consideration: it observed that “it is
impossible sensibly to discuss the question whether a physician was acting outside the usual
course of professional practice and without a legitimate medical purpose without mentioning the
usual standard of care.” Id. at 698.

       In United States v. Schneider, 704 F.3d 1287 (10th Cir. 2013), the Tenth Circuit arrived
at a similar conclusion. That case involved two doctors who were convicted of unlawful drug
distribution and health care fraud. The Government relied on experts who testified that one of
the defendants “prescribed controlled substances ‘for other than legitimate medical purposes.’”
Id. at 1294. Although the defendants challenged the admission of this testimony, their arguments
were unavailing. After observing that an “ultimate-issue” concern only arises when “an expert
No. 12-3212                         United States v. Volkman                   Page 12

uses a specialized legal term and usurps the jury’s function,” the Tenth Circuit concluded that the
experts’ use of the phrase “other than legitimate medical purposes” posed no issue. Id.

       Much like the Government’s experts in Chube II, the experts in this case merely provided
opinions suggesting that Volkman had no legitimate medical purpose for issuing a particular
prescription to a specific patient. See Chube II, 538 F.3d at 699. Certainly, there is the legal
question of whether a prescription had a “legitimate medical purpose,” but the question is hardly
answered in isolation. Rather, the “lay” or, as we have previously described it, “vernacular”
understanding of the phrase—i.e., the phrase as used in medical parlance—naturally informs the
legal question. See id. at 698. Therefore, the legal understanding of the phrase “legitimate
medical purpose” does not carry with it a “separate, distinct and specialized meaning” from its
medical counterpart; instead, one elucidates the other. See Torres, 758 F.2d at 151; see also
Schneider, 704 F.3d at 1294. We discern no error in the district court’s admission of the expert
colloquies that ended with the conclusion that certain prescriptions had no “legitimate medical
purpose.”

       Two exchanges, however, are worthy of separate discussion. Dr. Steven Severyn and an
area pharmacist, Mark Carroll, provided a medical-purpose conclusion on the stand, despite not
having been asked about a particular individual’s prescriptions. But even then, the questions
were appropriately limited to the standard of care and the evaluation of certain drug
combinations or drug quantities. Nothing in the record suggests that the two experts sought to
usurp the jury’s function by drawing a legal conclusion; instead, both experts applied their
understanding of the standard-of-care to a limited sample of facts. Accordingly, no error lies in
the admission of their testimony.

                                             IV.


       At the heart of Volkman’s appeal lies six sufficiency-of-the-evidence challenges. He
contends that there was insufficient evidence for the jury to convict him on the conspiracy and
firearm charges; in addition, he argues that there was insufficient evidence to convict him of the
drug-induced deaths of Kristi Ross, Steven Craig Hieneman, Bryan Brigner, and Earnest Ratcliff.
No. 12-3212                        United States v. Volkman                      Page 13

        In reviewing these convictions, we ask whether, “after construing the evidence in favor of
the Government, no rational trier of fact could have found the essential elements of a crime
beyond a reasonable doubt.” United States v. Ross, 703 F.3d 856, 882 (6th Cir. 2012). The
standard is a “steep climb,” id. (quotation omitted), and circumstantial evidence alone can defeat
a sufficiency challenge, United States v. Washington, 702 F.3d 886, 891 (6th Cir. 2012).

                                                A.

        We start with Volkman’s conviction under 21 U.S.C. § 846—the conspiracy charge. To
satisfy the statute’s requirements, “the government must prove the existence of an agreement to
violate the drug laws and that each conspirator knew of, intended to join, and participated in the
conspiracy.” United States v. Conrad, 507 F.3d 424, 432 (6th Cir. 2007) (quotation omitted).
“The connection between the defendant and the conspiracy need only be slight,” United States v.
Craft, 495 F.3d 259, 265 (6th Cir. 2007) (quoting United States v. Crayton, 357 F.3d 560, 573
(6th Cir. 2004)), and a “conspiracy may be inferred from circumstantial evidence which may
reasonably be interpreted as participation in a common plan,” Conrad, 507 F.3d at 432
(quotation omitted). In addition, “[a] tacit or material understanding among the parties to a
conspiracy is sufficient to establish the agreement.” Id. (quotation omitted).

        Volkman claims that he had no knowledge of the conspiracy’s “main purpose”—“to
make as much money as possible by distributing and dispensing controlled substances.” Instead,
he asserts that he was hired with the sole understanding that he would be serving as a pain
management physician.       The clinic was, in the ex-doctor’s view, a legitimate medical
operation—complete with in-house and hospital drug screens, pill counts, and in-clinic
monitoring of patients. According to Volkman, an illicit, drug-based profit motive did not fit
into the big picture.

        His recollection of events, however, turns a blind eye to quite a bit of evidence—
evidence that supports his conspiracy conviction. The conspiratorial relationship began when
Denise hired Volkman and paid him $5,500 per week in exchange for seeing those who wanted
pain medication. There was evidence to suggest that, by the time area physicians began refusing
to fill Volkman’s prescriptions, the purported members of the conspiracy—Denise, Alice, and
Volkman—were aware of the reality that the prescriptions from their clinic had no legitimate
No. 12-3212                        United States v. Volkman                    Page 14

medical purpose. Instead of rectifying the pharmacists’ issues with Volkman’s prescriptions, the
trio exacerbated the problem by continuing to issue prescriptions, cutting out the middleman, and
opening their own dispensary. This, by itself, was enough for a jury to find that the trio executed
a plan to unlawfully distribute controlled substances with no legitimate medical purpose.

       And contrary to his assertions, there was sufficient evidence to show that Volkman was
hardly the blissfully-ignorant doctor he now makes himself out to be. A rational trier of fact
could have easily concluded that the entire enterprise of dispensing pills straight from the clinic
was Volkman’s brainchild. That same trier of fact could have determined it was highly unlikely
that Volkman—a man who prided himself on knowing the inner workings of his clinic—was
unaware of the clinic’s profits. All this, combined with Volkman’s role in rubber-stamping the
distribution of prescriptions, could have easily persuaded a jury that Volkman knew of and
actively participated in the charged conspiracy.

                                                   B.

       The same holds true for Volkman’s firearm conviction.           He argues that there was
insufficient evidence to convict him of possessing a firearm in furtherance of a drug-trafficking
crime because (1) the Government did not establish possession; and (2) it did not prove that the
weapon was used in furtherance of a drug-trafficking offense. We disagree.

       First, we address the question of possession.       For purposes of the firearms statute,
“[c]onstructive possession is established when a defendant ‘knowingly has the power and the
intention at a given time to exercise dominion and control over an object, either directly or
through others.’” United States v. Kelsor, 665 F.3d 684, 692 (6th Cir. 2011) (quoting United
States v. Hadley, 431 F.3d 484, 507 (6th Cir. 2005)). Here, there was evidence showing that
Alice’s father placed the gun in the safe containing the drugs “for security purposes.” Volkman
had access to the safe. The record also reveals that he had concerns about personal security,
giving him a reason to use the gun should the need arise. Video evidence confirms that the
Glock was in the safe in 2005; Volkman was still working at the clinic at the time. This was
sufficient for a rational trier of fact to conclude that Volkman constructively possessed the
firearm for which he was indicted and convicted.
No. 12-3212                        United States v. Volkman                     Page 15

       But that does not end our inquiry, for Volkman argues that even if he constructively
possessed the firearm, the fact that it was in a locked safe meant that the weapon was not
possessed in furtherance of a drug crime, given its immediate inaccessibility. We, however, have
concluded otherwise in the past. When a weapon is found in a locked safe placed alongside
contraband, there is sufficient evidence for a jury to determine that a defendant is in possession
of a firearm in furtherance of a drug-trafficking crime. See United States v. Mendizabal, 214 F.
App’x 496, 501 (6th Cir. 2006); see also United States v. Cobbs, 233 F. App’x 524, 535-36 (6th
Cir. 2007) (concluding that there was sufficient evidence for a jury to find that a locked safe with
four handguns and crack cocaine nearby the safe constituted possession of a firearm in
furtherance of a drug offense). Hence, Volkman’s challenge to his firearm conviction must fail.

                                                C.

       The most serious of Volkman’s convictions are the ones for unlawful distribution of a
controlled substance leading to death. Volkman contends that a rational trier of fact could not
conclude that his prescription practices resulted in the deaths of Kristi Ross, Steve Hieneman,
Bryan Brigner, and Earnest Ratcliff.

       A violation of the CSA occurs when a physician dispenses or distributes a controlled
substance in a manner that is not authorized by law—i.e., the prescription is issued without “a
legitimate medical purpose by an individual practitioner acting in the usual course of his
professional practice.”   See 21 U.S.C. § 841(a)(1); 21 C.F.R. § 1306.04(a); see also Kirk,
584 F.2d at 784.    To determine whether a physician has violated the CSA, the jury may
undertake a “case by case analysis of evidence to determine whether a reasonable inference of
guilt may be drawn from specific facts.” Kirk, 584 F.2d at 784. When a physician violates the
CSA in a manner that leads to the death of a patient, there is a mandatory sentence of twenty
years to life in prison. See 21 U.S.C. § 841(b)(1)(C).

       The Supreme Court held in Burrage v. United States that, “at least where use the drug
distributed by the defendant is not an independently sufficient cause of the victim’s death or
serious bodily injury, a defendant cannot be liable for the penalty enhancement” under
§ 841(b)(1)(C). 134 S. Ct. at 892. In other words, use of the drug must have been a but-for
cause of the victim’s death or injury. Id. But-for causation exists where use of the controlled
No. 12-3212                               United States v. Volkman                            Page 16

substance “combines with other factors to produce” death, and death would not have occurred
“without the incremental effect” of the controlled substance. Id. at 888.

         In the present case, Volkman concedes that the district court properly gave the jury a
“but-for” causation instruction.”1 Specifically, the court instructed the jury:

         In order to establish that a death resulted from [d]efendant’s conduct, the
         government need not prove that the death was foreseeable to the defendant, but
         the government must prove beyond a reasonable doubt that the death would not
         have occurred had the mixture and substance containing a detectable amount of
         oxycodone, a Schedule II controlled substance dispensed by defendant, not been
         ingested by the individual.

(DE 482, PageID 8593-94.) The district court’s instruction notwithstanding, Volkman contends
that no rational trier of fact court have found, as the jury did here, that death would not have
occurred but-for the use of the oxycodone prescribed. We disagree. With respect to the deaths
of these four individuals, there was sufficient evidence for a jury to conclude that (1) Volkman
issued a prescription; (2) that had no legitimate medical purpose; (3) which was the but-for cause
the victim’s death. Thus, the Government satisfied its burden of proof under the CSA as
interpreted by the Supreme Court in Burrage.                  Although Volkman attempts to cherry-pick
evidence to dispute some aspect of each conviction, we are unpersuaded by his arguments.

                                                         1.

         First, we have Kristi Ross. On March 8, 2004, Ross—an obese, 39-year-old woman—
came into Volkman’s office, complaining of lower back pain, cervical myalgia, and
hypertension. Her pending divorce and her husband’s efforts to take custody of their daughter

         1
           In a pro se brief filed with this court’s permission and considered alongside the brief filed by his court-
appointed counsel, Volkman contends the jury instruction was incorrect and that his case must be “generally
remanded” back to the district court. According to Volkman, the instruction was incorrect because it is akin to the
“contributing-cause” instruction rejected by the Supreme Court in Burrage. 134 S. Ct. at 883-886, 892. We first
note that this argument is contrary to the argument made by his court-appointed counsel before the Supreme Court,
where counsel conceded that—even without the benefit of Burrage, which was subsequently decided—the
instruction was a correct statement of law. Volkman, 135 S. Ct. at 13. Counsel repeats this concession on remand.
Additionally, Volkman’s argument is wrong on the facts. The instruction provided by the district court here clearly
informed the jury that, in order for it to convict Volkman, the government must have proven “beyond a reasonable
doubt that death would not have occurred had the mixture and substance containing . . . oxycodone . . . dispensed by
[Volkman] . . . not been ingested by the individual.” Moreover, Volkman’s contention that this matter must be
“generally remanded” back to the district court in light of Burrage is without merit. The Supreme Court’s opinion
remanding this case to this court explicitly left intact Volkman’s other convictions. Id. at 14 (“The Court’s order,
moreover, has no bearing on petitioner’s other convictions for conspiracy to unlawfully distribute a controlled
substance, unlawful distribution of a controlled substance, maintaining a drug-involved premises, and possession of
a firearm in furtherance of a drug-trafficking offense.”).
No. 12-3212                        United States v. Volkman                     Page 17

compounded her stress.       Volkman prescribed a cocktail of Soma (carisoprodol), Lorcet
(hydrocodone), oxycodone, and Xanax (alprazolam). On this visit, and on Ross’ prior visit on
January 6, 2004, Volkman had increased her dosage of oxycodone while keeping constant her
prescriptions for hydrocodone, carisoprodol, and Xanax. (DE 296, PageID 3426-27.)

       Ross, however, suffered from a number of risk factors. In addition to her hypertension
and obesity, she potentially suffered from sleep apnea, as well as some form of lung disorder. In
other words, she was already at risk of breathing difficulties, and Volkman’s drug cocktail
exposed her to a greater risk of death. A rational trier of fact, relying on expert testimony, could
have found that there was no legitimate medical purpose for this combination of drugs.

       On March 9, 2004—one day after her last visit to Volkman—Ross was found dead, with
the very drugs prescribed to her in her purse. A toxicology report revealed that, at the time of
her death, Ross had benzodiazepines and opiates in her system—a toxic combination “consistent
with [Volkman’s] prescriptions.” (Id. PageID 3429.) Dr. Michael Policastro, a board certified
emergency room physician and toxicologist, concluded that Ross died of multi-drug death. (Id.)
The bottle of oxycodone in Ross’ purse contained 26 oxycodone pills; the prescription, filled the
day before, had been for 90 pills. (DE 448, PageID 6497-98.) This evidence of the increase in
Ross’ prescription for oxycodone just one day before her death—coupled with evidence that the
prescriptions for the other drugs found in her system remained constant—was sufficient for a
rational trier of fact to conclude that Volkman’s unlawful prescription of oxycodone was a but-
for cause of Ross’ death. Burrage, 134 S. Ct. at 892.

       Moreover, expert testimony corroborated the inherent risks of Volkman increasing Ross’
dosage of oxycodone. Dr. Policastro testified that doubling the daily dose of oxycodone, as
Volkman did here at Ross’ final visit, accelerates the risk that there will be a “[d]ecline of your
breathing.” (DE, PageID 3427.) Dr. Policastro further testified that while “your body can . . .
become[] tolerant to that breathing problem[,] . . . [a]s time progresses and doses of pain
medications increase, there is a point at which you cannot compensate for that.” (Id. PageID
3359.) Likewise, Dr. Kennedy testified that Volkman’s final oxycodone prescription to Ross
was “scary” and “extremely dangerous” if taken as prescribed, particularly when used in
combination with other drugs that also suppress breathing. (DE 301, PageID 3781-82.)
No. 12-3212                        United States v. Volkman                   Page 18

       Volkman takes issue with the accuracy of the post-mortem procedures used on Ross’
body—specifically, he argues that fluids should have been extracted from Ross’ femoral artery,
as opposed to her eye. While this argument may be perfectly valid, we are not in a position to
entertain it; it is for the jury to decide which evidence—scientific or otherwise—to credit in
making its determination. United States v. Washington, 715 F.3d 975, 979 (6th Cir. 2013) (citing
Jackson v. Virginia, 443 U.S. 307, 319 (1979)). It was well within the jury’s ambit for it to find
the methodology behind Ross’ forensic examination reliable.

       Volkman also advances the related argument that the concentration of oxycodone
extracted from Ross’ eye was below the level normally associated with death resulting from
oxycodone. This argument, however, is not inconsistent with Dr. Policastro’s testimony. Dr.
Policastro specifically testified that despite the fact that Ross’ “oxycodone level was slightly
below the range of levels associated with death,” death could nevertheless result due to the
“accelerating pattern of the dosages of the meds prior to death.” (DE 296, PageID 3429.) This
testimony, coupled with other testimony regarding the way in which oxycodone interacted with
the other drugs and Ross’ existing health risks (including her preexisting lung problems), was
sufficient for the jury to conclude that Volkman’s unlawful prescriptions resulted in Ross’ death,
thus justifying his conviction under § 841(b)(1)(C).

                                                2.

       Next, we have Steven Craig Hieneman.            Hieneman was a 33-year-old man with
cardiovascular problems. Volkman had seen Hieneman as a patient for quite some time—the
doctor had prescribed oxycodone in the past, mostly in five-milligram doses. Eventually, these
doses of oxycodone were ramped up to thirty-milligram doses. Hieneman saw Volkman on
February 22, 2005, complaining of pain in his wrist, neck, lower back, and shoulder. Hieneman
reported that, without medication, he was sleep-deprived, convulsed involuntarily in his hand
and shoulder, and his pain was above average.

       That day, Volkman prescribed Disalcid, Valium (diazepam), and Percocet (oxycodone) to
treat Hieneman’s ailments. On April 19, 2005, Volkman changed Hieneman’s prescriptions; he
issued prescriptions for Xanax (alprazolam), oxycodone, and Valium (diazepam).                The
No. 12-3212                        United States v. Volkman                     Page 19

prescriptions, particularly the one for oxycodone, were disturbing in light of the fact that
Hieneman had a past addiction to Oxycontin and was battling other forms of substance abuse.

       Volkman knew about Hieneman’s history, yet issued prescriptions for oxycodone. In
addition, the doctor knew he was prescribing these drugs to a man with severe hypertension and
heart problems associated with drug use. Given these dangers, a rational trier of fact could have
concluded—as one of the Government’s experts did—that Volkman’s prescription practices with
respect to Hieneman were not within the scope of legitimate medical practice.

       In addition, there was sufficient evidence for a rational jury to find but-for causation
between Hieneman’s prescription for oxycodone and his death. Hieneman died only twelve
hours after receiving his prescriptions from Volkman.         A deputy coroner concluded that
Hieneman died an opiate drug-induced death.        (DE 287, PageID 2800.)         Of the drugs in
Hieneman’s system, oxycodone was the only opiate. The signs were all there: Hieneman’s right
cheek was blanched, his airways were partly blocked, his eyes were hemorrhaged under the
conjunctivae, and he suffered from pulmonary edema.           The link to Volkman?        Bottles of
oxycodone, diazepam, and alprazolam were found in Hieneman’s home—i.e., the very drugs
Volkman prescribed to Hieneman the day before. Dr. Christian Rolf, a medical examiner and
board certified pathologist who performed Hieneman’s autopsy, testified the oxycodone in
Hieneman’s blood was “high enough [to constitute] a toxic level”—even for a person who had
built up a tolerance to oxycodone. (DE 287, PageID 2801, 2804.) Likewise, Dr. Policastro
testified that the level of oxycodone in Hieneman’s blood after his death was “within the range of
levels associated with deaths.” (DE 296, PageID 33443.)

       Volkman cites evidence identifying Hieneman’s cause of death as the “combined effects”
of oxycodone, diazepam, and alprazolam. The Government was not required to prove, however,
that oxycodone was Hieneman’s only cause of death. On the contrary, but-for causation exists
where a particular controlled substance—here, oxycodone—“combines with other factors”—
here, inter alia, diazepam and alprazolmam—to result in death. Burrage, 134 S. Ct. at 888. The
Government presented sufficient oxycodone-specific evidence for a rational jury to find that,
“without the incremental effect” of the oxycodone, Hieneman would not have died. Id.
No. 12-3212                        United States v. Volkman                   Page 20

       Volkman further argues that these very prescription bottles undermine the case against
him: the issuing doctor for one bottle of oxycodone was identified as a Dr. Scott Lance, not
Volkman. But there was sufficient evidence for the jury to discredit the theory that it was Lance,
and not Volkman, who was ultimately responsible for Hieneman’s death.

       First, Volkman’s patient notes acknowledged the existence of a Dr. Lance as a
prescribing physician for Hieneman, but remarked that Lance had prescribed only Valium
(diazepam). Relatedly, the notes indicated that Hieneman no longer had any of the medication
Lance prescribed for him; it was gone at least a month prior to Hieneman’s February 2005 visit
to Volkman’s clinic.      Second, while one bottle of oxycodone was labeled as having been
prescribed by Dr. Lance, the other bottles found at the scene did not have a prescribing physician
listed. Finally, there was a close temporal nexus between Volkman’s issuing of prescriptions and
Hieneman’s death. The relevance of this nexus is strengthened by the fact that Hieneman was
found dead with the very drugs Volkman prescribed.            Therefore, we conclude that the
Government provided sufficient causal evidence to link Volkman to Hieneman’s death.

       We are also unpersuaded by Volkman’s argument that Hieneman’s underlying heart
condition could have caused his death, irrespective of the drugs he consumed. The jury was free
to reject this theory by crediting the testimony of one of the Government’s experts, who
concluded that “there was no notation of clot, no notation of infarct, scar, plaque, hemorrhage or
anything like that,” thereby suggesting that coronary disease was not the primary cause of
Hieneman’s death.      Again, the existence of other potential contributing causes of death is
irrelevant so long as the Government presented sufficient evidence that oxycodone was a but-for
cause of Hieneman’s death. Burrage, 134 S. Ct. at 888.

                                                3.

       Following Hieneman, we have Bryan Brigner. On August 4, 2005, Brigner came to see
Volkman for treatment of his lower back pain. Brigner was disabled and had been on disability
benefits for several years. When Volkman spoke with Brigner, Brigner denied having any other
health problems. In truth, however, Brigner suffered from hypertension and arteriosclerotic
cardiovascular disease.
No. 12-3212                         United States v. Volkman                   Page 21

           When the two met that August day, Brigner was already on a regimen of Lortab
(hydrocodone), oxycodone, Valium (diazepam), and Soma (carisoprodol). The oxycodone made
him sick, so Volkman tried a smaller dose—but not for long. On September 30, 2005, Volkman
prescribed a similar cocktail of Soma (carisoprodol), Valium (diazepam), Disalcid (a non-
steroidal anti-inflammatory drug), Lortab (hydrocodone), and a strong dose of oxycodone. The
oxycodone prescription was for the same dose that made Brigner sick prior to his August visit.

           The new cocktail made little sense, especially given Brigner’s underlying cardiac
condition—a condition that weakened his ability to resist opiate toxicity. Volkman’s notes on
Brigner were also unhelpful; as one expert noted, it appeared as if there was “a lot of stuff . . .
but really the basics [weren’t] covered in a useful, functional, medical fashion, just a bunch of
stuff that’s thrown up there.” A rational trier of fact could have taken these facts and concluded
that Volkman’s prescriptions for Brigner did not bear the hallmarks of having a legitimate
medical purpose.

           As with Ross and Hieneman, Brigner was found dead shortly after his last visit with
Volkman. Brigner died within just forty-eight hours of this final visit. Two causes of death were
listed on the coroner’s report: acute multiple drug intoxication and cardiopulmonary arrest.
Brigner’s hypertension and arteriosclerotic cardiovascular disease were reported as contributing
factors.     A toxicology analysis revealed that Brigner had taken oxycodone, hydrocodone,
diazepam, haloperidol, and Sertraline just prior to his death.        The first three—the drugs
prescribed by Volkman—were enough to kill a person by respiratory depression. Put differently,
there was enough for a rational jury to conclude that Volkman’s drug cocktail led to Brigner’s
death.

           Despite this evidence, Volkman attacks his conviction on three evidentiary grounds.
First, he claims that if Brigner had taken Volkman’s prescribed medication as instructed, he
would not have overdosed because he would have built up a tolerance. Second, he asserts that
Sertraline and haloperidol—two drugs that Volkman did not prescribe but which were found in
Brigner’s system—could have been responsible for Brigner’s death. Third, he argues that
underlying heart conditions, such as cardiomegaly (an enlarged heart) or unstable plaque, could
have triggered the cardiac incident leading to Brigner’s death.
No. 12-3212                        United States v. Volkman                     Page 22

       For each one of these assertions, there is an evidentiary counterweight. First, a rational
jury could have credited Dr. Bryan Castro’s testimony that, of “[t]he medications . . . included
with [Brigner], none of them would give him opiate tolerance.” Second, while the evidence did
suggest that Sertraline and haloperidol can be lethal, they are only toxic in high doses not present
here. The trier of fact could have concluded that the levels in Brigner’s bloodstream were too
low to support such a theory. By contrast, testimony from both Dr. Castro and Dr. Kennedy
established that the level of oxycodone present in Brigner’s blood was toxic or potentially toxic.
(DE 315, PageID 4373; DE 300, PageID 3647-48, 3650.) Further, as with Ross, testimony
established that Brigner’s final prescription for oxycodone represented a significant increase
relative to his previous prescriptions. Dr. Kennedy testified that, at this final visit, Volkman
increased Brigner’s prescription for oxycodone from 30 mg a day to 240 mg a day. (DE 315,
PageID 4369.) On the same visit, Volkman kept constant his prescriptions for Valium and Soma
and increased only slightly the prescription for hydrocodone, from 60 mg to 80 mg. (Id.)

       Third, given the fact that there were no signs of a myocardial infarction—the usual
indicator of complications arising from arteriosclerotic cardiovascular disease—a rational trier of
fact was not compelled to accept Volkman’s argument that an underlying condition led to
Brigner’s death.

       Hence, we affirm this conviction.

                                                 4.

       Finally, we have Earnest Ratcliff. Ratcliff was a 38-year-old man suffering from pain in
his back, ankles, and feet. He had a history of drug addiction and minor drug dealing.

       Volkman saw Ratcliff on October 21, 2005.            The doctor issued prescriptions for
240 thirty-milligram doses of oxycodone, 90 doses of Soma (carisoprodol), 240 doses of Lortab
(hydrocodone), and 90 doses of Xanax (alprazolam)—660 pills in all. Given the sheer drug
quantity alone, a rational trier of fact could have concluded that there was no legitimate medical
purpose to the prescriptions, given the risk that Ratcliff would not comply with drug protocol and
the attendant risk of an adverse outcome.
No. 12-3212                         United States v. Volkman                   Page 23

       The next day, Ratcliff and his wife Melissa went to pick up the drugs from a drugstore in
Columbus. After obtaining the drugs, he proceeded to consume—or, more exactly, snort—the
pills on the way home. Ratcliff was lethargic and asleep for most of the drive. His wife found
his behavior unusual, in light of his past history with the drugs.

       Mrs. Ratcliff found her husband dead the next morning—just two days after his visit to
Volkman’s office. No autopsy was performed, but a toxicology report revealed that oxycodone,
methadone, hydrocodone, diazepam, and nordiazepam were in his bloodstream. From this, a
rational trier of fact had a sufficient evidentiary basis for concluding that Ratcliff’s death—
caused by “multi-drug intoxication”—was Volkman’s fault.

       Volkman argues that the methadone alone could have been lethal. Methadone, of course,
was the one drug that he did not prescribe. Indeed, he points out that one of the Government’s
own experts testified that the methadone was “very significant” in Ratcliff’s death.

       There was sufficient evidence, however, for a jury to disregard the possibility that
methadone acted as the lone lethal agent. First, it was a cumulative effect of toxicity, not a
single drug, that was responsible for Ratcliff’s death. Second, Ratcliff took methadone earlier in
the week—prior to taking the drugs that Volkman gave him—and was functional after
consuming the methadone. A jury could have used this as the basis for excluding the possibility
that methadone alone was responsible for Ratcliff’s death. Finally, a rational trier of fact could
have credited the testimony of the toxicologist who examined Ratcliff’s blood and agreed with
her conclusion that oxycodone, not methadone, was present in the “most significant level”
causing Ratcliff’s death. (DE 300, PageID 3642.) Accordingly, we conclude that there was
sufficient evidence to support Volkman’s conviction for unlawful distribution resulting in the
death of Earnest Ratcliff.

                                                 V.

       The final salvo of Volkman’s appeal attacks the reasonableness of his sentence. “This
Court reviews criminal sentences for both substantive and procedural reasonableness,” and uses
the “deferential abuse-of-discretion standard” to determine the propriety of the sentence. United
No. 12-3212                        United States v. Volkman                      Page 24

States v. Stubblefield, 682 F.3d 502, 510 (6th Cir. 2012) (citing Gall v. United States, 552 U.S.
38, 51 (2007); United States v. Battaglia, 624 F.3d 348, 350 (6th Cir. 2010)).

       Two of Volkman’s sentencing arguments focus on the district court’s application of
certain Guidelines enhancements.      Volkman also disputes the district court’s drug-quantity
determination. We construe these contentions as procedural reasonableness challenges. See
Stubblefield, 682 F.3d at 510; see also United States v. Daniels, 506 F. App’x 399, 399 (6th Cir.
2012) (treating a drug-quantity objection as a procedural-reasonableness issue).           As for
Volkman’s sentencing-disparity argument, we view that as a substantive reasonableness
challenge. See United States v. French, 505 F. App’x 478, 479-80 (6th Cir. 2012).

                                                A.

       Volkman first takes issue with the district court’s application of the vulnerable-victim
enhancement.     He asserts that the district court improperly based the enhancement on his
victims’ status as drug addicts.

       Section 3A1.1(b) of the Sentencing Guidelines provides for a two-level enhancement in
instances where “the defendant knew or should have known that a victim of the offense was a
vulnerable victim.” The Application Notes, however, state that the victim must be “an unusually
vulnerable victim.” U.S. Sentencing Guidelines Manual § 3A1.1(b) cmt. n.2 (emphasis added).

       In the past, we have acknowledged a tension between the Guideline language and the
Application Notes. See United States v. Lukasik, 250 F. App’x 135, 138 (6th Cir. 2007). We
need not resolve that tension today, however, because Volkman’s conduct fell within the
parameters of both.

       We agree with Volkman in concluding that drug addiction, standing alone, cannot serve
as the basis for applying the enhancement in cases such as this one. Drug addicts are not
necessarily vulnerable victims for purposes of section 3A1.1, and we decline to categorically
classify them as such. See United States v. Amedeo, 370 F.3d 1305, 1317 n.10 (11th Cir. 2004).

       But the circumstances of this case nevertheless support application of the enhancement.
See id. (noting that application of the enhancement is “highly fact-specific and must take into
No. 12-3212                        United States v. Volkman                    Page 25

account the totality of the circumstances”). It is true that the Pre-Sentence Investigation Report,
as well as the Government’s arguments at sentencing, focused heavily on the victims’ drug
addiction.    If this had been the sole basis for the district court’s decision to apply the
enhancement, then reversal would be warranted.

       The court, however, made additional findings regarding specific victims’ ailments. It
noted the mental and emotional frailties of some of Volkman’s patients by stating that “[s]ome
patients had serious psychiatric problems[,] [s]ome even had prior suicide attempts.” The court
made these observations based on statements that Volkman made during the sentencing
proceedings. We will not overturn a district court’s fact findings unless they are clearly
erroneous. See United States v. Moon, 513 F.3d 527, 539-40 (6th Cir. 2008). These fact findings
were not clearly erroneous. Under either the Guideline or its accompanying note, the findings
were sufficient to justify application of the vulnerable-victim enhancement. See U.S. Sentencing
Guidelines Manual § 3A1.1(b) cmt. n.2 (“[V]ulnerable victim means a person . . . who is
unusually vulnerable due to . . . mental condition[.]”). Therefore, we discern no abuse of
discretion here.

                                                B.

       Because we conclude that application of the vulnerable-victim enhancement was proper,
we must next address Volkman’s argument that applying both that enhancement and the special-
skill enhancement was impermissible double counting. Such double counting occurs when
“precisely the same aspect of the defendant’s conduct is factored into his sentence in two
separate ways.” United States v. Lay, 583 F.3d 436, 447 (6th Cir. 2009) (quoting United States
v. Farrow, 198 F.3d 179, 193 (6th Cir. 1999)) (quotation marks and modifications omitted).
“We review a district court’s legal conclusions regarding the Sentencing Guidelines de novo.”
Moon, 513 F.3d at 540 (citation omitted).

       The two enhancements at issue focus on different aspects of the case. Courts apply the
special-skill enhancement when a “defendant . . . use[s] a special skill, in a manner that
significantly facilitate[s] the commission or concealment of the offense.”       U.S. Sentencing
Guidelines Manual § 3B1.3. A special skill is defined as “a skill not possessed by members of
the general public and usually requiring substantial education, training or licensing.” Id. § 3B1.3
No. 12-3212                        United States v. Volkman                    Page 26

cmt. n.4. The Guideline notes specifically list doctors as one group of individuals possessing
special skills. Id. In contrast—and as the district court properly noted—the vulnerable-victim
enhancement focuses on the nature of the victim, as opposed to the offender. See id. § 3A1.1(b)
cmt. n.2.

       The fact that a defendant is a doctor—and his victim a patient—is insufficient for
applying the vulnerable-victim enhancement. See United States v. Stokes, 392 F. App’x 362, 371
(6th Cir. 2010) (“[T]he traditional doctor-patient relationship, on its own, provides an
insufficient basis for applying the vulnerable-victim enhancement.”). It is, however, sufficient
for applying the special-skill enhancement, especially in light of the fact that Volkman would not
have been in a position to abuse his prescription power without his medical license.           See
21 U.S.C. § 823(f) (detailing the CSA’s registration requirements); see also id. § 802(21)
(defining “practitioner”); United States v. Moore, 423 U.S. 122, 140 n.17 (1975). Given the
differences in how the enhancements apply, we discern no impermissible double-counting here.

                                                C.

       We can readily dispose of Volkman’s remaining arguments. First, Volkman argues that
the district court did not account for legitimate prescriptions in arriving at its drug-quantity
determination. Even if we assume that the district court erred by concluding that Volkman’s
drug-quantity determination warranted a base offense level of 38, such an error would be
harmless. Volkman’s convictions for unlawful distribution leading to death, standing alone,
warrant the same base offense level. See U.S. Sentencing Guidelines Manual § 2D1.1(a)(2)
(specifying a base offense level of 38 “if the defendant is convicted [under § 841(b)(1)(C)] . . .
and the offense of conviction establishes that death or serious bodily injury resulted from the use
of the substance”). Consequently, we could not reverse on this ground. See United States v.
Tandon, 111 F.3d 482, 491 (6th Cir. 1997) (holding that a tax-loss calculation error was harmless
because the base offense level would be unaffected).

       We are equally unpersuaded by Volkman’s sentencing-disparity argument. Four life
sentences, one for each § 841(b)(1)(C) conviction, may appear relatively disparate.          Other
doctors in a similar position may have been sentenced to a less lengthy term of imprisonment.
But each of Volkman’s life sentences fell within the applicable Guidelines ranges. When a
No. 12-3212                       United States v. Volkman                   Page 27

sentence is within-Guidelines, § 3553(a)(6) is an improper vehicle for challenging that sentence.
See United States v. Swafford, 639 F.3d 265, 270 (6th Cir. 2011). Thus, we conclude that
Volkman’s sentence was substantively reasonable.

                                              VI.

       We AFFIRM Volkman’s convictions and sentence.
