United States v. Stephen McFadden ( 2014 )


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  •                              PUBLISHED
    UNITED STATES COURT OF APPEALS
    FOR THE FOURTH CIRCUIT
    No. 13-4349
    UNITED STATES OF AMERICA,
    Plaintiff - Appellee,
    v.
    STEPHEN DOMINICK MCFADDEN, a/k/a Stephen Domin McFadden,
    Defendant - Appellant.
    Appeal from the United States District Court for the Western
    District of Virginia, at Charlottesville. Glen E. Conrad, Chief
    District Judge. (3:12-cr-00009-GEC-1)
    Argued:   March 19, 2014                  Decided:   May 21, 2014
    Before TRAXLER, Chief Judge, and WILKINSON and KEENAN, Circuit
    Judges.
    Affirmed by published opinion. Judge Keenan wrote the opinion,
    in which Chief Judge Traxler and Judge Wilkinson joined.
    ARGUED:   J.   Lloyd    Snook,   III,  SNOOK    &   HAUGHEY,   PC,
    Charlottesville, Virginia, for Appellant.    Jean Barrett Hudson,
    OFFICE OF THE UNITED STATES ATTORNEY, Charlottesville, Virginia,
    for Appellee.      ON BRIEF: Timothy J. Heaphy, United States
    Attorney, Roanoke, Virginia, Ronald M. Huber, Assistant United
    States   Attorney,   OFFICE   OF  THE  UNITED   STATES   ATTORNEY,
    Charlottesville, Virginia, for Appellee.
    BARBARA MILANO KEENAN, Circuit Judge:
    This   appeal      concerns    a   defendant’s      convictions    involving
    the sale of “designer drugs,” in violation of the Controlled
    Substance Analogue Enforcement Act of 1986 (the Act), 21 U.S.C.
    §§ 802(32)(A), 813.         Stephen D. McFadden was convicted by a jury
    of nine charges stemming from his distribution of substances
    that the government alleged were prohibited by the Act.                         On
    appeal,      McFadden      primarily          asserts     that   the     Act    is
    unconstitutionally vague as applied to him, that the district
    court     abused   its     discretion     in     making    certain     evidentiary
    rulings at trial, and that the government failed to prove that
    the   substances      McFadden      distributed     qualified    as     controlled
    substance analogues under the Act.                Upon our review, we affirm
    the district court’s judgment.
    I.
    Before addressing the facts of this case and McFadden’s
    challenges to his convictions, we first provide a brief overview
    of the Act.        Congress enacted the Act to prevent “underground
    chemists” from creating new drugs that have similar effects on
    the human body as drugs explicitly prohibited under the federal
    drug laws.     See United States v. Klecker, 
    348 F.3d 69
    , 70 (4th
    Cir. 2003); see also United States v. Hodge, 
    321 F.3d 429
    , 432,
    437 (3d Cir. 2003) (purpose of the Act is to “make illegal the
    2
    production    of   designer   drugs   and    other   chemical      variants    of
    listed   controlled   substances      that   otherwise    would     escape     the
    reach of the drug laws”).          To achieve that purpose, Congress
    mandated that a “controlled substance analogue,” when intended
    for   human   consumption,    be   treated     under     federal    law   as    a
    Schedule I controlled substance.          21 U.S.C. § 813.
    Subject to certain exceptions not at issue in this case, a
    “controlled substance analogue” is defined under the Act as:
    a substance-
    (i) the chemical structure of which is substantially
    similar to the chemical structure of a controlled
    substance in schedule I or II;
    (ii)   which   has   a   stimulant,   depressant,   or
    hallucinogenic effect on the central nervous system
    that is substantially similar to or greater than the
    stimulant, depressant, or hallucinogenic effect on the
    central nervous system of a controlled substance in
    schedule I or II; or
    (iii) with respect to a particular person, which such
    person represents or intends to have a stimulant,
    depressant, or hallucinogenic effect on the central
    nervous system that is substantially similar to or
    greater    than   the    stimulant,   depressant,   or
    hallucinogenic effect on the central nervous system of
    a controlled substance in schedule I or II.
    21 U.S.C. § 802(32)(A).
    Accordingly, an individual may be convicted for an offense
    involving a controlled substance analogue under 21 U.S.C. § 841
    if the government establishes that: (1) the alleged analogue
    substance has a chemical structure that is substantially similar
    to the chemical structure of a controlled substance classified
    3
    under     Schedule          I    or   Schedule          II   (the     chemical       structure
    element); 1 (2) the alleged analogue substance                                  has an actual,
    intended       or   claimed        stimulant,           depressant,      or      hallucinogenic
    effect    on     the    central        nervous          system    that     is     substantially
    similar to or greater than such effect produced by a Schedule I
    or    Schedule         II       controlled        substance         (the        pharmacological
    similarity element); and (3) the analogue substance is intended
    for   human     consumption           (the    human       consumption         element).      See
    
    Klecker, 348 F.3d at 71
    (construing 21 U.S.C. §§ 802(32)(A),
    813).
    II.
    In July 2011, police investigators in the Charlottesville,
    Virginia area began investigating the use and distribution of
    certain       synthetic         stimulants        commonly       known     as    “bath   salts.”
    When ingested into the human body, bath salts are capable of
    producing       similar         effects      as    certain        controlled        substances,
    including cocaine, methamphetamine, and methcathinone.
    The    police       investigation          revealed       that     bath     salts   were
    being sold from a video rental store in Charlottesville, which
    was owned and operated by Lois McDaniel.                                 Using confidential
    1
    Controlled substances are classified under one of five
    schedules, which are set forth in 21 U.S.C. § 812 and 21 C.F.R.
    §§ 1308.11 through 1308.15.
    4
    informants,      investigators   purchased       bath       salts   from    McDaniel,
    which later were analyzed by the United States Drug Enforcement
    Administration (DEA).          The chemical analysis performed by the
    DEA     showed      that      these      bath       salts         contained        3,4-
    methylenedioxypyrovalerone                    (MDPV)                and           3,4-
    methylenedioxymethcathinone           (methylone,      or    MDMC).        Government
    agents later seized from McDaniel’s store additional bath salts
    that contained a combination of MDPV, methylone, and 4-methyl-
    ethylcathinone (4-MEC).
    McDaniel agreed to cooperate with the investigators, and
    informed them that the bath salts she distributed from her store
    were supplied by McFadden.              At the investigators’ direction,
    McDaniel    initiated        recorded        telephone       conversations        with
    McFadden in which she placed orders for bath salts.                              During
    these conversations, McFadden discussed the potency and duration
    of the “high” experienced by users of the substances he was
    distributing.      He also compared the effects of those substances
    to    certain     controlled     substances,        including         cocaine      and
    methamphetamine.
    As a result of these transactions, investigators received
    bath salts supplied by McFadden on five separate occasions.                        The
    DEA’s   analysis    showed    that     two    batches       of   these    bath   salts
    contained 4-MEC, MDPV, and methylone.                  The three other batches
    5
    contained    4-MEC,     but     not   MDPV         or   methylone. 2        Based       on   the
    findings    of     this    investigation,               the    grand    jury      issued      a
    superseding indictment in November 2012, charging McFadden with
    nine offenses, including one count of conspiracy to distribute
    substances containing the alleged controlled substance analogues
    4-MEC, MDPV, and methylone (collectively, the alleged CSAs), and
    eight additional counts of distributing these substances. 3
    The   four-day      jury    trial        focused        primarily     on    the    issue
    whether     4-MEC,      MDPV,     and      methylone           constitute        controlled
    substance    analogues        under      the       Act.       To    prove   the     chemical
    structure element, the government presented the testimony of Dr.
    Thomas DiBerardino, a chemist employed by the DEA, who qualified
    as   an   expert   in     the    field    of       chemical        structures     of    drugs.
    2
    During the course of the government’s investigation, the
    DEA, under its emergency temporary scheduling powers in 21
    U.S.C. § 811(h), classified MDPV and methylone as Schedule I
    controlled substances.   Schedules of Controlled Substances, 76
    Fed. Reg. 65371, 65372 (amending 21 C.F.R. § 1308.11) (Oct. 21,
    2011). The government did not allege that McFadden distributed
    MDPV or methylone after this classification.
    3
    The indictment contained the following charges: conspiracy
    to distribute a substance or mixture containing the controlled
    substance analogues 4-MEC, MDPV, and methylone, in violation of
    21 U.S.C. §§ 841(a)(1), (b)(1)(c) and 846 (Count One); two
    counts of distribution of a substance or mixture containing MDPV
    and methylone, in violation of 21 U.S.C. §§ 841(a)(1) and
    (b)(1)(c) (Counts Two and Three); three counts of distribution
    of a substance or mixture containing 4-MEC, MDPV, and methylone,
    in violation of 21 U.S.C. §§ 841(a)(1) and (b)(1)(c) (Counts
    Four, Five, and Six); and three counts of distribution of a
    substance or mixture containing 4-MEC, in violation of 21 U.S.C.
    §§ 841(a)(1) and (b)(1)(c) (Counts Seven, Eight, and Nine).
    6
    Using      chemical    diagrams        as        demonstrative        exhibits,      Dr.
    DiBerardino testified that the chemical structures of 4-MEC and
    MDPV are each substantially similar to methcathinone, a Schedule
    I   controlled   substance.        Dr.          DiBerardino       further   testified,
    based on the chemical diagrams, that the chemical structure of
    methylone is substantially similar to ecstasy, which also is a
    Schedule I controlled substance.
    To   establish     the   pharmacological           similarity       element,   the
    government presented the testimony of Dr. Cassandra Prioleau, a
    drug science specialist employed by the DEA, who qualified as an
    expert in the field of pharmacological effects of drugs.                             Dr.
    Prioleau     testified    that    4-MEC         and     MDPV   each   would      have   a
    pharmacological        effect     on        the         central     nervous       system
    substantially similar to the effect produced by methcathinone.
    Dr.   Prioleau   further       testified         that    methylone       would   have   a
    substantially     similar      pharmacological            effect    on    the    central
    nervous system as ecstasy. 4
    In his defense, McFadden presented the testimony of Dr.
    Matthew C. Lee, a primary care physician and pharmacist, who
    qualified as an expert in the field of pharmacology and the
    4
    Dr. Prioleau acknowledged during cross-examination that
    methylone generally produced only about one-half the stimulant
    effect of ecstasy, but also noted that at a “maximum dosage”
    level methylone and ecstasy would have equivalent stimulant
    effects.
    7
    effects of medication.               Dr. Lee criticized the methodology used
    by Dr. DiBerardino in reaching his conclusions regarding the
    chemical structure element, and further stated that MDPV and
    methcathinone are not similar in chemical structure. 5                                    Dr. Lee
    also       criticized      the    methodology      employed        by       Dr.    Prioleau     in
    reaching      her    conclusions        with    respect       to      the    pharmacological
    similarity element.               Dr. Lee testified that methylone did not
    produce      similar       pharmacological         effects       as    ecstasy,         and    that
    there was insufficient scientific data to draw a conclusion that
    4-MEC and MDPV produce similar pharmacological effects in humans
    as methcathinone.
    After hearing this and other evidence, the jury returned a
    verdict       finding      McFadden     guilty       of     each   of       the    nine    counts
    alleged       in    the     indictment.         At      a    sentencing           hearing,     the
    district       court        found     that     McFadden’s          advisory          sentencing
    guidelines         range     was      between      51       months’      and       63     months’
    imprisonment.             After considering the factors set forth in 18
    U.S.C. § 3553(a), the court imposed a below-guidelines sentence
    of     33    months’        imprisonment        for       each     conviction,            to   run
    concurrently,         and     a     30-month    period        of      supervised        release.
    McFadden filed a timely notice of appeal.
    5
    Dr. Lee did not make an explicit conclusion during his
    testimony about whether 4-MEC and methcathinone, or methylone
    and ecstasy, were substantially similar in their respective
    chemical structures.
    8
    III.
    A.
    We    first   consider      McFadden’s      argument          that       the     Act    is
    unconstitutional as applied to him.                    This argument presents the
    central      theme   that    the    Act    failed       to     provide      a     person       of
    ordinary      intelligence      notice     that    the       conduct       at     issue       was
    unlawful.
    McFadden      argues     that       the     Act       fails         to     meet        the
    constitutional requirement of notice because: (1) the Act uses a
    “standards-based”       scheme,          employing       general       terms          such     as
    “substantially       similar”      and    “human     consumption,”              and   lacks     a
    list    of    prohibited      substances;        (2)     the    Act    is        subject       to
    arbitrary      and   discriminatory         enforcement         in    the        absence       of
    statutory      guidance      concerning         prohibited          conduct;          and     (3)
    despite      significant      efforts       on     his       part     to        learn       about
    prohibited conduct, McFadden was unable to determine “what he
    can and cannot do,” and was unaware that the distribution of
    controlled substance analogues is prohibited under federal law.
    We review de novo a challenge to the constitutionality of a
    federal statute.          United States v. Gibert, 
    677 F.3d 613
    , 618
    (4th Cir. 2012).            As a general matter, a criminal statute is
    unconstitutionally vague if it does not sufficiently define an
    offense such that ordinary people can understand what conduct is
    prohibited.       Kolender v. Lawson, 
    461 U.S. 352
    , 357 (1983).                              This
    9
    inquiry generally requires an examination of what a person of
    “common intelligence” would reasonably understand the statute to
    prohibit, rather than what a particular defendant understood the
    statute to mean.     See United States v. Washam, 
    312 F.3d 926
    , 930
    (8th Cir. 2002) (citing United States v. Nat’l Dairy Prods., 
    372 U.S. 29
    , 32-33 (1963) and Connally v. Gen. Constr. Co., 
    269 U.S. 385
    , 391 (1926)).     Additionally, a statute is unconstitutionally
    vague if its definition of the prohibited conduct encourages
    arbitrary and discriminatory enforcement.                
    Kolender, 461 U.S. at 357-58
    .
    In our decision in Klecker, we rejected a nearly identical
    constitutional challenge as that raised by McFadden.                      
    See 348 F.3d at 71-72
    .       There, a defendant challenged his convictions
    for distributing a chemical compound commonly known as “Foxy.”
    
    Id. at 71.
       The government alleged that Foxy was an analogue of
    a Schedule 1 controlled substance, diethyltryptamine (DET).                   
    Id. at 70.
       We held that the Act was not unconstitutionally vague in
    its use of the term “substantially similar” with respect to a
    defendant    who   lacked   actual    notice      that    a   substance    was    a
    controlled substance analogue.            
    Id. at 72.
         We observed that the
    considerable similarities, found from a comparison of chemical
    diagrams of the alleged analogue substance and the controlled
    substance,    were   sufficient      to    “put   a    reasonable    person      on
    notice” of Foxy’s composition as a DET analogue.               
    Id. 10 This
    holding in Klecker defeats McFadden’s argument that
    the    term   “substantially             similar,”           as       used    in    21     U.S.C.        §
    802(32)(A),       is    unconstitutionally                 vague       when     applied         to    the
    chemical      compounds         at      issue     here.            The       testimony          of     Dr.
    DiBerardino       comprehensively               addressed          the       chemical       diagrams
    comparing      the      chemical         structures          of       4-MEC     and      MDPV        with
    methcathinone, and methylone with ecstasy.
    Presenting two-dimensional diagrams in which the chemical
    structures of 4-MEC and MDPV were displayed in an overlapping
    manner     with      the     chemical         structure            of       methcathinone,            Dr.
    DiBerardino       explained           that      these        substances            share        a    core
    chemical      structure,             namely        that       of        a     compound              called
    phenethylamine.            Although the overlapping diagrams showed that
    the    substances          each      have       some       unique        features          in        their
    respective chemical compositions, Dr. DiBerardino testified that
    these unique features do not affect the chemical core of the
    substances.       Rather, he stated that the diagrams reflected that
    “[e]verything          that’s     different           is    on     the       periphery”         of     the
    respective chemical structures.                       Dr. DiBerardino made the same
    type     of   comparison             examining         the        chemical         structures           of
    methylone     and      ecstasy,         during     which         he     explained        that        those
    substances        share           the       same           core         chemical         structure,
    phenethylamine,          and      that    the      structural            differences            between
    methylone and ecstasy are insignificant.
    11
    Based on his evaluation of these diagrams of the chemical
    compounds      at     issue,        Dr.     DiBerardino        concluded          that    the
    controlled      substances       and       the     respective     alleged        CSAs    have
    substantially         similar        chemical          structures.               Thus,     Dr.
    DiBerardino applied the statutory term “substantially similar”
    in evaluating the core chemical structures of the substances at
    issue,   and    was    able    to    distinguish         the   differences         in    those
    structures as peripheral and inconsequential.                           After reviewing
    these    chemical     diagrams,        we    agree      with   the     district        court’s
    conclusion that for purposes of satisfying the constitutional
    requirement of notice, there are substantial similarities in the
    chemical      structures        between          the    alleged      CSAs        and     their
    controlled substance counterparts.
    We also view the chemical diagrams and Dr. DiBerardino’s
    testimony in light of the evidence concerning McFadden’s intent
    that    the    alleged    CSAs      be      consumed      by   humans       to    produce   a
    stimulant effect.         See 
    Klecker, 348 F.3d at 72
    (observing that
    defendant’s      intent    that      Foxy        be    ingested   as    a    hallucinogen
    reinforced the conclusion that the defendant had adequate notice
    that Foxy would be regarded as a DET analogue).                                   As stated
    above,    McFadden       informed         McDaniel      during    recorded        telephone
    conversations that the substances he was distributing produced
    12
    effects similar to certain controlled substances. 6                           The fact that
    McFadden intended that the substances he was distributing be
    used       as      alternatives        to      controlled            substances          further
    demonstrates        that     a   reasonable           person    in    his    position      would
    understand that his conduct was prohibited by the Act.                                   See 
    id. In view
    of this evidence, the district court did not err in
    concluding that the statutory term “substantially similar,” as
    applied here, would put a reasonable person on notice concerning
    the proscribed conduct.
    We       further    disagree     with          McFadden’s      argument      that     the
    statutory term “human consumption” is unconstitutionally vague.
    See 21 U.S.C. § 813.                  Although McFadden notes correctly that
    this term is not defined in the Act, the lack of a statutory
    definition does not render the Act unconstitutional per se.                                  See
    Chapman      v.    United    States,        
    500 U.S. 453
    ,    462,   467-68       (1991)
    (holding that 21 U.S.C. § 841(b)(1)(B) is not unconstitutionally
    vague       despite       lack   of    statutory             definition      of    the     terms
    “mixture”         and   “substance”).             A    statute       need    not   contain     a
    definition of every term within its text, and, in the absence of
    a statutory definition, courts will give terms their ordinary
    6
    As discussed later in this opinion, we disagree with
    McFadden’s argument that the district court erred in admitting
    the recorded telephone conversations into evidence.  See infra
    at 20-21.
    13
    meaning.     See United States v. Day, 
    700 F.3d 713
    , 725 (4th Cir.
    2012) (citing 
    Chapman, 500 U.S. at 462
    , 467-68).
    We agree with the district court that, in the context of
    the Act, the ordinary meaning of the term “human consumption”
    plainly encompasses the use of a substance by a human being in a
    manner that introduces the substance into the body.                        See Black’s
    Law Dictionary 359 (9th ed. 2009) (defining “consumption” as
    “the use of a thing in a way that exhausts it”).                       We therefore
    conclude that there is no ambiguity or vagueness in the Act’s
    use of the term “human consumption.”
    Additionally, we reject McFadden’s argument that the Act is
    unconstitutionally vague because it does not provide a list of
    substances        that    qualify     as    controlled      substance       analogues.
    Because     the     Act    provides       for    the   comparison     of     different
    chemical compounds to determine whether they are “substantially
    similar,”    a     list    of    particular      chemical      compounds    could    not
    encapsulate the variety of substances potentially covered by the
    Act.      Moreover,       such   a   requirement       would    undermine    the    very
    purpose    of     the     Act,    which    is    to    prevent    individuals       from
    creating    slightly       modified       versions     of   controlled      substances
    that produce similar effects and entail similar dangers as those
    controlled substances.            See 
    Klecker, 348 F.3d at 70
    ; 
    Hodge, 321 F.3d at 432
    , 437.
    14
    Given    the     creativity      of   individuals         manufacturing        these
    analogue substances, see United States v. Hofstatter, 
    8 F.3d 316
    , 322 (6th Cir. 1993), there is genuine potential that the
    creation       of     such    substances       could     outpace    any     efforts      by
    authorities to identify and catalog them.                        Thus, we decline to
    extend    our       holding    in    Klecker      by   imposing     a    constitutional
    notice requirement that the Act contain a list of prohibited
    substances.          See United States v. Fisher, 
    289 F.3d 1329
    , 1337
    n.11 (11th Cir. 2002) (rejecting vagueness challenge and noting
    that     “[n]o        list     of     controlled        substance        analogues       is
    necessary”).
    We also find no merit in McFadden’s argument that the Act
    is subject to arbitrary and discriminatory enforcement.                           We held
    in Klecker that the Act’s “intent requirement alone tends to
    defeat    any       vagueness       challenge     based    on    the     potential      for
    arbitrary 
    enforcement.” 348 F.3d at 71
    .          We explained that this
    intent    element       requires      that   the       government       prove    that   the
    defendant meant for the substance at issue to be consumed by
    humans.      Id.; see also United States v. Roberts, 
    363 F.3d 118
    ,
    126    (2d     Cir.    2004)    (holding        that    the     “intended       for   human
    consumption”         element    protects     against      arbitrary       enforcement).
    Arbitrary and discriminatory enforcement further is prevented by
    the additional statutory requirements that the government prove
    (1) substantial chemical similarity between the alleged analogue
    15
    substance      and    the     controlled        substance,          and     (2)     actual,
    intended, or claimed pharmacological similarity of the alleged
    analogue substance and the controlled substance.                            See 
    Klecker, 348 F.3d at 71
    .             Accordingly, we reject McFadden’s arguments
    that   the    Act    failed    to    provide     him    adequate          notice    of    the
    prohibited      conduct        and     was      subject        to     arbitrary           and
    discriminatory enforcement.
    We likewise find no merit in McFadden’s argument that the
    Act is unconstitutional as applied because he “took reasonable
    steps to inform himself as to the legality of the chemicals that
    he was selling,” and did not find any information indicating
    that his actions were illegal.                  In support of this argument,
    McFadden relies on the fact that he visited the DEA’s website to
    determine whether the substances at issue were prohibited, but
    that he did not see the disclaimers on the website discussing
    the Act and controlled substance analogues.
    McFadden’s     argument       fails     because    it    flouts        the     well-
    settled    general     principle      that     “ignorance      of     the     law    is    no
    excuse.”      See United States v. Mitchell, 
    209 F.3d 319
    , 323 (4th
    Cir. 2000) (citation omitted).                 Moreover, McFadden provides no
    authority supporting his novel proposition that we should depart
    from   this    general      rule     because    he     unsuccessfully         sought      to
    determine     whether    his       conduct     was   lawful.         Accordingly,          we
    reject    McFadden’s     argument       that    the     Act    is    unconstitutional
    16
    because he lacked notice that the distribution of controlled
    substance analogues is prohibited under federal law.
    B.
    We     next   address      McFadden’s   arguments    concerning     certain
    rulings made by the district court during the trial.                       McFadden
    contends that the district court erred: (1) in permitting the
    testimony of Toby Sykes, an individual who purchased bath salts
    from       McDaniel;   (2)   in    admitting   into    evidence    recordings     of
    McFadden’s      telephone      conversations    with    McDaniel;    and    (3)   in
    declining to instruct the jury that the government was required
    to prove that McFadden effectively knew that the substances at
    issue had the essential characteristics of controlled substance
    analogues.
    1.
    The     government      offered   the   testimony    of    Toby   Sykes    as
    evidence       supporting      the    pharmacological      similarity      element.
    Sykes testified that he was a former methamphetamine addict who
    purchased bath salts from McDaniel, and that his use of these
    bath salts produced a far more potent effect on his body than
    his use of methamphetamine. 7
    7
    Although Sykes compared the bath salts to methamphetamine
    rather than methcathinone, Dr. Prioleau testified that various
    studies showed that MDPV and methylone produce a similar
    pharmacological effect in laboratory animals as the effect
    generated by methamphetamine.     Accordingly, as the district
    (Continued)
    17
    McFadden     objected         to   Sykes’      testimony         on   the   ground    of
    relevance, because it was uncertain whether the bath salts that
    Sykes consumed had been supplied by McFadden or were in the same
    form and doses as those delivered to McDaniel.                                  The district
    court    overruled        McFadden’s       objection,         but       granted     him    “great
    latitude”     to    cross-examine          Sykes      concerning          whether     he    could
    state    that      the    substances        he     purchased        were      distributed     by
    McFadden. 8
    We review for abuse of discretion a district court’s ruling
    concerning       the     admissibility        of      evidence.          United     States    v.
    Summers, 
    666 F.3d 192
    , 197 (4th Cir. 2011).                              Under Rule 402 of
    the   Federal       Rules        of   Evidence,        all    “relevant”          evidence    is
    admissible unless specifically prohibited by the Constitution, a
    federal    statute,         or    another      evidentiary          rule.         Evidence    is
    relevant if it has a tendency to make a fact pertinent to the
    case “more or less probable than [the fact] would be without the
    evidence.”       Fed R. Evid. 401; United States v. Powers, 
    59 F.3d 1460
    ,     1465     (4th     Cir.      1995).          We     have       observed     that    the
    determination          of    relevance           “presents          a     low     barrier     to
    court   found,   Sykes’  comparison   of   the   bath  salts  to
    methamphetamine was consistent with Dr. Prioleau’s testimony.
    8
    On appeal, McFadden bases his argument concerning Sykes’
    testimony on relevancy grounds, and does not argue that the
    testimony should have been struck under Federal Rule of Evidence
    403 as having a probative value substantially outweighed by the
    danger of unfair prejudice.
    18
    admissibility,”              and     that     evidence             need     only     be     “worth
    consideration by the jury” to be admissible.                                 United States v.
    Leftenant, 
    341 F.3d 338
    , 346 (4th Cir. 2003) (citation omitted).
    Accordingly,            a     district       court           has    broad       discretion       in
    determining whether certain evidence is relevant.                                  United States
    v. Queen, 
    132 F.3d 991
    , 998 (4th Cir. 1997).
    Applying this deferential standard of review, we conclude
    that       the    district         court    did        not    abuse       its    discretion      in
    admitting Sykes’ testimony.                       As McFadden concedes, there was
    some overlap between the period in which Sykes purchased bath
    salts from McDaniel and the period in which McFadden supplied
    McDaniel         with       such    substances.              Also,        importantly,      Sykes’
    description of the packaging of the bath salts he purchased from
    McDaniel         matched      the    description             of    the     packaging      used   by
    McFadden         in   distributing          the    substances.               Sykes    was   shown
    several exhibits of “blue baggies” containing substances that
    the government agents had purchased from McDaniel and, on at
    least one occasion, directly from McFadden.                                     Sykes testified
    that he recognized the packaging of those exhibits because he
    had purchased bath salts from McDaniel in similar blue baggies. 9
    9
    McDaniel was also shown these exhibits during her
    testimony, during which she stated that she recognized those
    items as originating from McFadden because of their distinctive
    packaging.
    19
    Given this foundation evidence tending to show that some of
    the   bath    salts      consumed    by    Sykes     were   supplied     by   McFadden,
    Sykes’ testimony concerning the bath salts’ effect on his body
    properly was submitted to the jury for purposes of establishing
    the   pharmacological           similarity    element.       Although      there      were
    flaws in Sykes’ testimony relating to the time period at issue
    and whether McDaniel altered the substances after receiving them
    from McFadden, such flaws were explored during cross-examination
    and were relevant to the weight to be given Sykes’ testimony,
    not to its admissibility.             See Ziskie v. Mineta, 
    547 F.3d 220
    ,
    225   (4th    Cir.      2008)    (noting     that    determining     the      weight    of
    evidence entails a different inquiry than the relevance inquiry
    required by Rules 401 and 402 of the Federal Rules of Evidence).
    2.
    We next consider McFadden’s challenge to the admission of
    evidence     of     recorded     telephone        conversations     between     him    and
    McDaniel.         In    the    district    court,     McFadden    objected      to    this
    evidence on the ground that the comparisons he made during these
    conversations were irrelevant to the crimes charged, because he
    claimed      that      4-MEC    produced     effects    similar     to   cocaine       and
    methamphetamine, controlled substances not used for comparison
    under   the       chemical      structure     element.        The    district        court
    overruled McFadden’s objection, finding that this evidence was
    20
    relevant to both the pharmacological similarity element and the
    human consumption element.
    On appeal, McFadden argues solely that the district court
    erred in concluding that the recordings were relevant to the
    pharmacological similarity element.               McFadden does not address
    the district court’s separate conclusion that this evidence was
    relevant to the human consumption element, nor does he raise an
    argument that admission of this evidence was unduly prejudicial
    under Rule 403.         Because the human consumption element was an
    independent basis for the district court’s admission of this
    evidence, we affirm the court’s ruling on that basis and do not
    address McFadden’s argument whether the recordings were relevant
    to proof of the pharmacological similarity element.                   See United
    States   v.     Hatchett,   
    245 F.3d 625
    ,    644-45    (7th     Cir.   2001)
    (holding defendant waived argument concerning district court’s
    ruling on admissibility of evidence by failing to challenge on
    appeal one of two independent grounds for court’s ruling).
    3.
    McFadden    next    asserts,    on    the    basis    of   out-of-circuit
    precedent, that the district court erred in refusing to instruct
    the jury that the government was required to prove that he knew,
    had a strong suspicion, or deliberately avoided knowledge that
    the   alleged    CSAs    possessed   the   characteristics       of    controlled
    substance analogues.         See United States v. Turcotte, 
    405 F.3d 21
    515, 527 (7th Cir. 2005).                 We review for abuse of discretion the
    district court’s denial of the requested instruction.                                          United
    States v. Bartko, 
    728 F.3d 327
    , 343 (4th Cir. 2013).                                    To show an
    abuse    of    discretion,          a     defendant          must      establish         that     the
    proffered       instruction:             “(1)         was       correct,         (2)     was      not
    substantially        covered        by   the     charge         that   the       district       court
    actually      gave    to     the    jury,       and       (3)    involved        some    point       so
    important that the failure to give the instruction seriously
    impaired the defendant’s defense.”                        
    Id. McFadden’s argument
    fails at the outset because he cannot
    satisfy the first requirement of this test.                               The instruction he
    proposed is not a correct statement of the law in this Circuit.
    In Klecker, we set forth the elements that the government was
    required      to     prove     to       obtain        a     conviction       under       the     Act,
    including the scienter requirement that the defendant intended
    that the substance at issue be consumed by 
    humans. 348 F.3d at 71
    .     We    further        stated      that     the        Act    may     be    applied       to    a
    defendant who lacks actual notice that the substance at issue
    could be a controlled substance analogue.                           
    Id. at 72.
    In contrast to our decision in Klecker, the Seventh Circuit
    has imposed a strict knowledge requirement before a defendant
    may be convicted of violating the Act.                                 In its decision in
    Turcotte, the court stated that “our precedents demand a showing
    that    the    defendant        knew      the         substance        in    question       was      a
    22
    controlled substance 
    analogue.” 405 F.3d at 527
    .           Because we
    have   not   imposed        such   a    knowledge      requirement,      and    have   not
    included     the      concepts     of    “strong       suspicion”      or    “deliberate
    avoidance” in framing the scienter requirement under the Act, we
    hold    that        the     district     court       properly       denied     McFadden’s
    requested jury instruction.
    C.
    Finally,      we     address     McFadden’s      argument      challenging      the
    sufficiency of the evidence and the district court’s denial of
    his motion for judgment of acquittal.                        McFadden’s sufficiency
    argument is limited to his contention that the government failed
    to satisfy its evidentiary burden of demonstrating that 4-MEC,
    MDPV, and methylone qualify as controlled substance analogues.
    McFadden     does     not    otherwise     contest      the     jury’s      verdict    with
    respect to the conspiracy offense and the substantive counts of
    distributing controlled substance analogues in violation of the
    Act.
    We review de novo the district court’s denial of a motion
    for judgment of acquittal.               United States v. Hamilton, 
    699 F.3d 356
    , 361 (4th Cir. 2012).               In considering a defendant’s argument
    that the evidence was insufficient to support his convictions,
    we will uphold a jury’s verdict if, viewing the evidence in the
    light most favorable to the government, there is substantial
    evidence       in     the     record     to        support    the     verdict.          
    Id. 23 “Substantial
    evidence” is “evidence that a reasonable finder of
    fact       could    accept     as     adequate          and    sufficient         to    support        a
    conclusion of a defendant’s guilt beyond a reasonable doubt.”
    United States v. Green, 
    599 F.3d 360
    , 367 (4th Cir. 2010).
    In conducting this review, we afford the jury’s verdict
    deference          because     “it    is   the      jury’s          province      to    weigh        the
    credibility of the witnesses, and to resolve any conflicts in
    the evidence.”           United States v. Dinkins, 
    691 F.3d 358
    , 387 (4th
    Cir.       2012)     (citation        omitted).               Accordingly,          a     defendant
    challenging the sufficiency of the evidence on appeal bears a
    “heavy       burden,”         and     we      will        reverse          a    conviction           for
    insufficient          evidence        “only         in     the       rare       case    when         the
    prosecution’s failure is clear.”                          
    Hamilton, 699 F.3d at 361-62
    (citation and internal quotation marks omitted).
    For     ease      of    review,        we        restate      the       elements       of     the
    distribution         offenses        for   which         McFadden        was    convicted.            In
    addition to proving that McFadden distributed the substances at
    issue,       the     government         was        required         to     prove       that        those
    substances: (1) have a substantially similar chemical structure
    as     a    Schedule      I    or     II   controlled             substance;        (2)       have     a
    substantially similar or greater pharmacological effect on the
    human central nervous system as a Schedule I or II controlled
    substance,          which      effect      was          either      actual,        intended,          or
    represented         by   the    defendant;          and       (3)    were      intended       by     the
    24
    defendant to be consumed by humans.                   See 
    Klecker, 348 F.3d at 71
    .
    As stated above, the government presented the testimony of
    Dr.    DiBerardino,          who     concluded     that    4-MEC    and    MDPV    are
    substantially similar in chemical structure as methcathinone, a
    Schedule I controlled substance.                  The government also presented
    the testimony of Dr. Prioleau, who concluded that 4-MEC and MDPV
    produce    a    substantially          similar      pharmacological       effect    as
    methcathinone.       McFadden asks us to cast aside Dr. DiBerardino
    and Dr. Prioleau’s opinions and adopt the conflicting views of
    McFadden’s expert witness, Dr. Lee.                   According to Dr. Lee, the
    scientific methods employed by Dr. DiBerardino and Dr. Prioleau
    were    inadequate      to    reach     their     respective    conclusions,       with
    which Dr. Lee disagreed.
    We recognized long ago that “[a]n appellate court is not
    the    proper   forum    to        refight   a    battle   of   expert    witnesses.”
    Connorton v. Harbor Towing Corp., 
    352 F.2d 517
    , 518 (4th Cir.
    1965) (per curiam), quoted in United States v. Wood, 
    741 F.3d 417
    , 425 (4th Cir. 2013).              That fight was waged in the district
    court in this case, and the jury chose to accept the conclusions
    of Dr. DiBerardino and Dr. Prioleau, despite defense counsel’s
    vigorous cross-examination of those witnesses and the opposing
    testimony of Dr. Lee.
    25
    It     would   be     improper    under      our     standard      of    review    to
    elevate Dr. Lee’s opinion over the opinions of Dr. DiBerardino
    and Dr. Prioleau, because it is the jury’s function to weigh
    witnesses’ credibility, to determine the weight to be accorded
    their       testimony,     and   to    resolve      conflicts       in    the     evidence.
    
    Dinkins, 691 F.3d at 387
    ; United States v. Maceo, 
    873 F.2d 1
    , 7
    (4th Cir. 1989).             Therefore, based on the record before us, we
    conclude that the government presented sufficient evidence that
    4-MEC and MDPV are substantially similar in chemical structure
    as methcathinone, a Schedule 1 substance.                         We further conclude
    that the government presented sufficient evidence that 4-MEC and
    MDPV    produce       actual     pharmacological          effects    on     the    central
    nervous system substantially similar to the effects produced by
    methcathinone. 10        In light of this conclusion concerning “actual”
    pharmacological          similarity,      we       need    not    address       McFadden’s
    argument that there was insufficient proof that he “represented
    or     intended”      that     4-MEC    and    MDPV       would   have    substantially
    similar pharmacological effects as a controlled substance. 11                            See
    10
    We note that because the jury’s verdict is well-supported
    by Dr. DiBerardino and Dr. Prioleau’s testimony, we need not
    consider Sykes’ testimony in determining whether the government
    proved actual pharmacological similarity of these substances at
    issue.
    11
    We therefore need not reach McFadden’s arguments
    concerning his statements to McDaniel that 4-MEC and mixtures
    containing 4-MEC have an effect similar to substances other than
    (Continued)
    26
    
    Klecker, 348 F.3d at 71
      (government         may    establish        the
    pharmacological similarity element by showing “actual, intended,
    or claimed” similarity) (emphasis added).
    Having reached this conclusion with respect to 4-MEC and
    MDPV, we need not address whether there was sufficient evidence
    in     the    record    to    conclude   that      methylone       qualified    as    a
    controlled      substance      analogue.       Each     of   the   charges     in    the
    superseding indictment relating to methylone also alleged in the
    conjunctive that McFadden distributed MDPV or 4-MEC with respect
    to those counts.         In other words, none of the charges hinged on
    a finding that methylone qualified as a controlled substance
    analogue. 12         Accordingly,   even      if   we   agreed     with   McFadden’s
    arguments relating to methylone, we nevertheless would affirm
    each of his convictions.            See Turner v. United States, 
    396 U.S. 398
    ,    420    (1970)     (reaffirming     the     general     rule    that    if    an
    indictment charges several acts in the conjunctive, a guilty
    verdict stands if the evidence is sufficient with respect to any
    one of the acts); United States v. Bollin, 
    264 F.3d 391
    , 412
    methcathinone, and do not decide whether the pharmacological
    similarity element may be established by comparing the alleged
    analogue substance to a different controlled substance than used
    for comparison under the chemical structure element.
    12
    We further observe that because the government agreed to
    remove methylone from the calculation of drug weight for
    purposes    of   determining   McFadden’s   advisory  sentencing
    guidelines range, methylone was not a factor in the court’s
    determination of McFadden’s sentence.
    27
    n.14   (4th    Cir.    2001)    (in   case    involving       perjury    allegation
    charged   in    the    conjunctive     pertaining        to    two   alleged   false
    statements,     holding        that   Court    need      not     reach   arguments
    pertaining to the first alleged false statement because evidence
    supported     jury    verdict    relating     to   the    second     alleged   false
    statement).
    IV.
    For these reasons, we affirm the district court’s judgment.
    AFFIRMED
    28