                             UNPUBLISHED

                  UNITED STATES COURT OF APPEALS
                      FOR THE FOURTH CIRCUIT


                             No. 13-4063


UNITED STATES OF AMERICA,

                Plaintiff – Appellee,

           v.

JOHN STACKS,

                Defendant – Appellant.


Appeal from the United States District Court for the Western
District of North Carolina, at Charlotte.     Frank D. Whitney,
Chief District Judge. (3:11-cr-00371-FDW-DCK-1)


Argued:   January 30, 2014                    Decided:   May 8, 2014


Before KING, WYNN, and FLOYD, Circuit Judges.


Affirmed by unpublished per curiam opinion.


ARGUED: Joshua B. Carpenter, FEDERAL DEFENDERS OF WESTERN NORTH
CAROLINA, INC., Asheville, North Carolina, for Appellant.
William Michael Miller, OFFICE OF THE UNITED STATES ATTORNEY,
Charlotte, North Carolina, for Appellee.     ON BRIEF: Henderson
Hill, Executive Director, FEDERAL DEFENDERS OF WESTERN NORTH
CAROLINA, INC., Charlotte, North Carolina, for Appellant.   Anne
M. Tompkins, United States Attorney, OFFICE OF THE UNITED STATES
ATTORNEY, Charlotte, North Carolina, for Appellee.



Unpublished opinions are not binding precedent in this circuit.
PER CURIAM:

     John Stacks appeals his conviction for being a felon in

possession       of    a   firearm,      in    contravention       of     18    U.S.C.

§ 922(g)(1).           Stacks   first    challenges      the    district       court’s

denial of his motion to suppress evidence obtained as a result

of   a    traffic      stop,    maintaining      that     the     officers      lacked

reasonable suspicion that he was engaged in criminal activity.

Stacks    also    contends      that    his    conviction      should    be    vacated

because    the    court    improperly     and    prejudicially       admitted       lay

opinion testimony of a police officer.                   As explained below, we

reject the contention with respect to the suppression issue,

discern no prejudicial error regarding the challenged testimony,

and thus affirm Stacks’s conviction.



                                          I.

                                          A.

     Around four o’clock the morning of March 18, 2011, Officers

Bryan Overman and Chandos Williams of the Charlotte-Mecklenburg

Police    Department       were    assigned       to     patrol    the     “Westpark

Corridor,”       surrounding      Westpark      Drive,    in    Charlotte,       North

Carolina.        The    Westpark   Corridor,      a    commercial       area   on   the

western side of Charlotte near Interstate 77, is home to several

hotels, restaurants, and nightclubs.                  The area was known to the

police, including Officers Overman and Williams, as a “hot spot

                                          2
for   breaking    and   entering      motor    vehicle    cases,”      particularly

during the early morning hours.                See J.A. 31. 1       As such, the

officers were dispatched to the Westpark Corridor the morning of

March 18 to “do some surveillance on the hotels and along that

corridor   for    the   prevention     of     larceny    from   auto    or   vehicle

break-ins.”      Id.    At the time, Overman had been a police officer

for more than seventeen years, nearly twelve of which were with

the Charlotte-Mecklenburg Police Department, and nine of those

in the Steele Creek Division, where the Westpark Corridor is

located.        Williams    had   been      with   the    Charlotte-Mecklenburg

Police    Department     for   more    than     twenty    years,    and      spent   a

majority of that time working in the Steele Creek Division.

      After arriving at the Westpark Corridor and conducting an

initial sweep of the area, the officers parked their unmarked

patrol car in a business park.                They turned off the headlights

and the internal lights in the vehicle.                  From that vantage, the

officers could observe the parking lots of several of the hotels

on Westpark Drive.         Despite the early morning hour, the parking

lots and street were well-lit.                The officers observed just “a

handful”   of    people,    mostly     employees    and    deliverymen        at   the

hotels.    See J.A. 34.


      1
       Citations herein to “J.A. ___” refer to the contents of
the Joint Appendix filed by the parties in this appeal.



                                         3
       At approximately 4:30 a.m., the officers observed a brown

two-door     Cadillac   drive    past   them    on   Westpark   Drive.      The

Cadillac was driven by an African-American male later identified

as Stacks, and there were no other passengers in the car.                    As

the Cadillac passed the officers’ parked unmarked vehicle, the

officers observed the Cadillac’s driver looking to his right,

towards the hotels and parking lots.             The officers did not see

the driver look in their direction.

       After passing the officers, the Cadillac turned into the

parking lot of a Residence Inn and drove “up and down the rows

of cars in the hotel parking lot.”             J.A. 37.     The Cadillac then

proceeded to the parking lot of the next hotel, again driving

through the rows of parked cars without stopping or lingering.

According to Officer Williams, it appeared the Cadillac’s driver

was either looking for a parking space or was lost.                      As the

Cadillac exited the second parking lot and approached a third

hotel (the last hotel on Westpark Drive before it dead-ended

into    a   cul-de-sac),   the   officers   decided    to   “stay   with”   the

Cadillac and started driving towards the third hotel.                    Id. at

38.     The officers left the headlights of their unmarked vehicle

dark.       After driving through the third hotel parking lot, the

Cadillac pulled back onto Westpark Drive, driving north away

from the hotels and the cul-de-sac.            At that point, the officers

were driving the opposite direction — towards the last hotel at

                                        4
the end of the cul-de-sac.               As the cars passed one another,

Stacks saw the officers, turned around completely in his seat to

look at them, and slowed the brown Cadillac down, “almost coming

to a stop.”   Id. at 39.

     Upon observing Stacks’s reaction, the officers decided to

initiate a traffic stop and activated the blue lights on their

vehicle.    Stacks pulled the Cadillac over, and Officer Overman

approached the vehicle and requested Stacks’s driver’s license

and registration.         After Overman returned to the police vehicle

to   run   Stacks’s       license     and       registration    through        the   DMV

database, Officer Williams approached the Cadillac and began to

question   Stacks.         Williams    asked       Stacks   why    he    was    in   the

Westpark Corridor, and Stacks responded that he was dropping off

his girlfriend, Kenia Boo; however, Stacks could not tell the

officers   where     he    had   taken      her. 2     While      he    was    standing

alongside the Cadillac questioning Stacks, Williams observed a

“camouflage jacket that was in the back seat spread out almost

like it was covering something.”                 J.A. 74.      Williams, cognizant

that he was “out there looking for people that had been breaking

     2
       Stacks provided the officers with Ms. Boo’s name and a
telephone number, which the officers called later that morning.
Boo spoke with Officer Williams, but failed to corroborate
Stacks’s claim that he had been dropping her off that morning.
Stacks subsequently called the officers back from that same
number and attempted to explain why he had fled from the traffic
stop.



                                            5
into    cars,”     thought      that    the    jacket    could     be     concealing

something because he had seen other defendants “hide stuff in

the back seat, in the trunk, underneath the seats of the car,

that kind of stuff.”         Id. at 75.

       After    learning   that    Stacks      had   previously    been     arrested

several    times    for    armed       robbery,      Officer    Overman    rejoined

Officer Williams alongside the Cadillac.                 Overman recalled that

Stacks looked “obviously nervous” in that he was talking fast

and “fumbling around with his phone in his car.”                    J.A. 43.    The

officers asked Stacks to step out of the car.                        In response,

Stacks asked the officers if they had probable cause for their

request.       The officers explained that they did not need probable

cause   and     again   asked   Stacks    to    exit    the    vehicle,   whereupon

Stacks pulled away from the curb and sped off.                       The officers

returned to their vehicle and chased Stacks, but were not able

to apprehend him.          The officers thereafter obtained an arrest

warrant for Stacks for resisting, delaying, and obstructing the

officers, as well as for careless and reckless driving, all in

violation of North Carolina law.

       Several hours later, at approximately 8:00 a.m. on March

18, a guest at one of the hotels along Westpark Drive found a

firearm underneath some bushes outside the Residence Inn and




                                          6
gave it to a police officer he saw in the area. 3                     The firearm,

which was later used as evidence in prosecuting Stacks, was a

Cobra Enterprises Model CA-380 semiautomatic pistol.

     Stacks       turned    himself    in    to     the    Charlotte-Mecklenburg

Police    later    that     morning.        While    Stacks    was    in   custody,

Detective Jimmy Messer interviewed him and asked him about the

pistol recovered from the bushes on Westpark Drive.                    Stacks told

Messer that he did not know anything about the firearm.                       Later

that day, while in jail on the obstruction and reckless driving

charges, Stacks made five telephone calls to an unidentified

female.    During those calls, which were recorded, Stacks made

several incriminating statements about getting rid of a firearm,

referring to the weapon as a “gun,” a “burner,” and an “iron.”

See J.A. 516, 525, 541-42, 556-59, 580.

                                        B.

     On November 15, 2011, a federal grand jury in the Western

District    of    North     Carolina   returned       an    indictment     charging

Stacks    under    18     U.S.C.   § 922(g)(1)       with     being   a    felon   in


     3
       The Residence Inn’s parking lot is the first of the three
that the officers observed Stacks drive through on the morning
of March 18, 2011.     The Residence Inn was therefore located
within a few hundred yards of the spot on Westpark Drive where
Stacks was stopped by Officers Williams and Overman. The bushes
where the pistol was found later that morning were on the left
of the road, in the direction from which Stacks fled from the
traffic stop.



                                        7
possession of a firearm on March 18, 2011.                     On February 22,

2012, Stacks moved to suppress all of the evidence derived from

the traffic stop — including his identity and his statements

made during the stop and after his arrest, as well as the pistol

recovered from the bushes on Westpark Drive — asserting that the

stop     violated     his    Fourth    Amendment     right     to    be     free       of

unreasonable      searches     and    seizures.     At   the   conclusion         of    a

February 27, 2012 suppression hearing, the district court took

Stacks’s motion under advisement and directed the parties to

brief the following issue:              Assuming, arguendo, that the stop

was unconstitutional, “what is fruit of the poisonous tree and

what    is    not,    starting   with     the   identity     of     the     defendant

himself.”      J.A. 129.       After unsuccessfully urging the court to

immediately decide the suppression motion solely on the basis of

the constitutionality of the stop, the prosecution asserted that

all of the evidence was admissible under either an inevitable

discovery theory or the good faith exception to the exclusionary

rule.       Stacks challenged both contentions, maintaining that all

of    the    government’s     evidence    was     tainted    as     fruit    of    the

poisonous traffic stop.

        On May 15, 2012, after conducting a supplemental hearing,

the    district      court   denied    Stacks’s   suppression       motion.        See

United States v. Stacks, No. 3:11-cr-00371 (W.D.N.C. May 15,



                                          8
2012) (the “Order”). 4     In so doing, the court first ruled that

the   stop    of   Stacks’s   vehicle    “was      based    on    reasonable,

articulable    suspicion   that   criminal   activity      was   afoot,”    and

specified nearly a dozen factors in support of that conclusion.

See Order 9. 5     The court further determined that, even if it had

      4
          The district court’s unpublished Order is found at J.A.
258-71.
      5
       The district court articulated that the following nine
factors amounted to “reasonable articulable suspicion” that
supported the stop of Stacks’s Cadillac:

      •      “The area in which the officers were conducting
             surveillance, first saw Defendant, and conducted
             the traffic stop was an area well known to the
             officers specifically for automobile larceny and
             vehicle    break-ins,    which   the    Charlotte–
             Mecklenburg Police Department called a hot spot
             for breaking and entering motor vehicle cases”;

      •      “The officers were conducting surveillance, and
             Defendant was present, during a time of night
             that is typical for automobile larcenies and
             vehicle break-ins to occur”;

      •      “Defendant drove down Westpark Drive continually
             looking only in the direction of the hotel
             parking lots”;

      •      “Defendant was alone       in   his    vehicle      at   all
             relevant times”;

      •      “Defendant drove up and down the rows of parked
             cars in three different hotel parking lots
             without   parking,   stopping,  dropping off  a
             passenger, or picking up a passenger”;

      •      “While driving up and down the rows of parked
             cars, Defendant was continually looking in the
             direction of the parked cars”;
(Continued)
                                    9
deemed   the    stop      unconstitutional,       “much   of    the    evidence    in

question would not be subject to exclusion.”                Id. at 13. 6

     Thereafter,       prior      to    trial,    the   prosecution      identified

Detective      James      Helms    of    the     Charlotte-Mecklenburg        Police

Department     as    an    expert      witness    who   would    “provide     expert

testimony as to the general jargon and slang terminology used

for firearms.”       J.A. 274.         Stacks objected to the designation of

Helms    as   an    expert   witness,      contending     that    he    lacked     the

requisite expertise to testify as an expert.                      Stacks further




     •        “Defendant exited each hotel parking lot and
              immediately entered another, exhibiting the same
              behavior in three (3) different hotel parking
              lots”;

     •        “When Defendant saw the officers,                 who    were   in
              uniform, he slowed down”; and

     •        “When Defendant saw the officers, he turned
              around in his seat 180 degrees to look at the
              officers.”

Suppression Order 9-10 (internal quotation marks omitted).
     6
       The district court’s alternative ruling was based on two
theories.    First, the court deemed the firearm abandoned
property, meaning Stacks had no standing to challenge its
seizure. Second, the court reasoned that when Stacks “fled the
scene, he committed a new and distinct crime,” and evidence
“seized as a result of the new crime, such as the telephone
calls from jail while under arrest for the new crimes would
still be admissible.”    Id. Because we discern no error as to
the court’s reasonable suspicion determination, we need not
reach its alternative ruling on the admissibility of the
evidence against Stacks.



                                          10
asserted      that    because        the    terms     “burner”     and   “iron”      are

“commonly used in popular culture,” expert testimony as to the

meaning of those terms was not necessary or appropriate.                       Id. at

276-77.       And,    Stacks       maintained      that   any    probative   value    of

Helms’s expert testimony would be outweighed by prejudice to

Stacks because Helms would also be testifying as a fact witness.

During pretrial proceedings, the district court ruled that Helms

would “not be qualified as an expert,” but would be permitted to

testify — “from his experience as a law enforcement officer” —

about hearing “slang terms ‘burn[er]’ and ‘iron’ referring to

firearms.”     Id. at 285.

    At trial, the prosecution called nine witnesses, including

Detective      Helms,        and     introduced       the       recordings    of     the

incriminating phone calls that Stacks made from jail on March

18, 2011.      Helms testified that he recognized Stacks as the male

voice on the recordings.                   Helms further testified as to his

understanding        of    the     recorded       conversations,     including     that

“burner” and “iron” are slang terms for a firearm.                       On June 5,

2012,   the    jury       returned    a    verdict    convicting     Stacks   of     the

charged 18 U.S.C. § 922(g)(1) offense.                    On January 15, 2013, the

district court sentenced Stacks to 212 months in prison.                         Stacks

timely noticed this appeal, and we possess jurisdiction pursuant

to 28 U.S.C. § 1291.



                                             11
                                       II.

                                        A.

     We first address Stacks’s challenge to the district court’s

ruling on his suppression motion — that is, his contention that

the officers lacked reasonable suspicion to justify the March

18, 2011 traffic stop.         In considering a district court’s ruling

on a motion to suppress, we review de novo the court’s legal

conclusions, while reviewing its underlying factual findings for

clear error.        See United States v. Foster, 634 F.3d 243, 246

(4th Cir. 2011).        A court’s determination that the facts of a

citizen-police encounter give rise to reasonable suspicion is a

legal   one,    which   we   review    de    novo.    See   United    States    v.

Foreman, 369 F.3d 776, 782 (4th Cir. 2004).                    As the Supreme

Court has instructed, in assessing determinations of reasonable

suspicion, the courts of appeals are to “give due weight to

inferences drawn from those facts by resident judges and local

law enforcement officers.”            Ornelas v. United States, 517 U.S.

690, 699 (1996).        Finally, where, as here, the government has

prevailed      in   opposing   a   suppression       motion,   we    review    the

evidence in the light most favorable to the government.                        See

United States v. Davis, 690 F.3d 226, 233 (4th Cir. 2012).

                                        1.

     The Fourth Amendment “prohibits unreasonable searches and

seizures by the Government, and its protections extend to brief

                                        12
investigatory stops of persons or vehicles that fall short of

traditional arrest.”          United States v. Arvizu, 534 U.S. 266, 273

(2002) (internal quotation marks omitted).                        In the nearly fifty

years that have passed since issuing its seminal decision in

Terry    v.   Ohio,    392     U.S.     1    (1968),       the    Supreme      Court     has

frequently revisited the issue of reasonableness in the context

of traffic stops and made clear that an investigatory stop “is

permissible     under        the     Fourth       Amendment        if    supported        by

reasonable     suspicion”       that        criminal       activity     may    be    afoot.

Ornelas, 517 U.S. at 693.

     Reasonable suspicion requires that an officer “be able to

articulate something more than an inchoate and unparticularized

suspicion or hunch” that criminal activity may be afoot.                             United

States   v.   Sokolow,    490      U.S.      1,   7   (1989)      (internal     quotation

marks omitted).        In making reasonable-suspicion determinations,

reviewing     courts     are       to     “look       at    the    totality         of   the

circumstances of each case to see whether the detaining officer

ha[d] a particularized and objective basis for suspecting legal

wrongdoing.”     Arvizu, 534 U.S. at 273 (internal quotation marks

omitted).     The Supreme Court has recognized that “the concept of

reasonable     suspicion        is      somewhat       abstract,”        and     reminded

reviewing courts that officers are allowed “to draw on their own

experience and specialized training to make inferences from and

deductions about the cumulative information available to them

                                             13
that    might   well    elude      an   untrained   person.”   Id.     (internal

quotation marks omitted).               Importantly, “the fact that the stop

occurred in a high crime area [is] among the relevant contextual

considerations”        in   this   analysis;    however,   “[a]n    individual’s

presence   in   an     area   of    expected    criminal   activity,    standing

alone, is not enough to support a reasonable, particularized

suspicion that the person is committing a crime.”                   Illinois v.

Wardlow, 528 U.S. 119, 124 (2000).

                                           2.

       Applying the foregoing standards, we conclude that Officers

Williams and Overman had reasonable suspicion to stop Stacks’s

Cadillac in the predawn hours of March 18, 2011.                   We consider,

as we must, the reasonableness of the officers’ suspicions in

light of the totality of the circumstances, and we address all

of the supporting factors in turn.

       We first consider the relevant — though not dispositive —

fact that Stacks was in a high crime area when he was pulled

over.    Specifically, Stacks was driving in an area known as a

hot spot for breaking and entering into automobiles — precisely

the type of crime that the officers were assigned to prevent and

in which they suspected Stacks might be engaged.                   Although this

factor “carries no weight standing alone, an area’s disposition

toward criminal activity is an articulable fact, that may be

considered along with more particularized factors to support a

                                           14
reasonable suspicion.”         United States v. Sprinkle, 106 F.3d 613,

617   (4th    Cir.   1997)    (citations        and    internal    quotation      marks

omitted).

        In   addition    to   being   a   high        crime    area,    the   Westpark

Corridor is also an entirely commercial area consisting of a

strip    of    hotels,    restaurants,         and    nightclubs       near   a   major

interstate.      As such, the area was extremely quiet in the early

morning hours of March 18.            Indeed, the officers observed “very,

very little traffic” other than Stacks while they surveilled the

area, namely “a handful” of workers and deliverymen going in and

out of the hotels on the strip.                J.A. 34.       The suspiciousness of

Stacks’s conduct — driving slowly in and out of three hotel

parking lots without making any stops — was compounded by the

time of day.      See United States v. Smith, 396 F.3d 579, 587 (4th

Cir. 2005) (observing that lateness of the hour may raise level

of suspicion); see also Wardlow, 528 U.S. at 129-30 (Stevens,

J., concurring in part and dissenting in part) (observing that

“[f]actors such as the time of day, the number of people in the

area, [and] the character of the neighborhood” may be relevant

in the reasonable suspicion analysis).                  Indeed, Stacks’s conduct

was more consistent with someone preparing to engage in criminal

activity than with any of the legitimate activities occurring on

Westpark Drive at that hour.



                                          15
       Stacks’s      reaction       to    the    officers         further     supports         the

officers’ reasonable suspicion.                       Having observed Stacks drive

slowly through two parking lots without stopping, the officers

drove   toward       Stacks,     and     the     two      vehicles       passed     as    Stacks

exited a third hotel parking lot.                          Upon seeing the officers,

Stacks slowed his car substantially, coming almost to a complete

stop, and craned himself around to look at the officers as they

passed.       Such a reaction, in Officer Overman’s words, “sparked

[the officers’] interest.”                 J.A. 39.              Coupled with the early

hour,   the     commercial      nature      of      the    area,     and    the     Cadillac’s

driving    slowly         through    the    parking         lots,        Stacks’s     reaction

cemented      the    officers’      reasonable            suspicion       that    Stacks       was

engaged in, or about to engage in, criminal activity.

       Stacks       nevertheless         contends         that     the     officers       lacked

reasonable suspicion because the stop was based on nothing more

than a vague hunch, thus falling far short of the reasonable

suspicion required by the Fourth Amendment.                               We disagree.          As

this    Court       has   previously       explained,            “factors     that       may   be

‘susceptible of innocent explanation’ when taken in isolation

can combine to ‘form a particularized and objective basis’ for a

stop when considered together.”                     United States v. Bumpers, 705

F.3d 168, 174-75 (4th Cir. 2013) (quoting Arvizu, 534 U.S. at

277-78).        That      is   certainly        the    case       here.      Stacks       could,

perhaps, provide a reasonable and legal explanation for each of

                                               16
the    factors:           the    high   crime      area,     the    early    morning       hour,

driving slowly without stopping, and the reaction to the police.

Nevertheless, the whole of the circumstances facing the officers

the morning of March 18 is greater than the sum of its parts.

Considering, as we must, the totality of the circumstances, the

officers      possessed          reasonable     suspicion       that      Stacks     may    have

been engaged in criminal activity.

                                                B.

       We next consider Stacks’s contention that the trial court

committed          reversible      error      in     allowing       Detective       Helms     to

testify       as     to    his     understanding        of    slang       terminology       for

firearms.          We review a district court’s evidentiary rulings for

abuse of discretion.                See United States v. Johnson, 617 F.3d

286,   292     (4th       Cir.    2010).      Moreover,        as    we    have     explained,

evidentiary rulings “are subject to harmless error review under

Federal Rule of Criminal Procedure 52, such that in order to

find a district court’s error harmless, we need only be able to

say    with    fair       assurance,       after     pondering       all     that    happened

without stripping the erroneous action from the whole, that the

judgment      was     not       substantially        swayed    by    the     error.”        Id.

(internal quotation marks omitted).

       Stacks       maintains       that    because        Detective        Helms    was    not

qualified as an expert, his opinion testimony should have been

limited to his personal observations of the conversations at

                                                17
issue.      As there is no question that Helms did not personally

observe his calls from jail, Stacks contends, Helms should not

have been permitted to opine on the slang terms Stacks used in

those calls.      We agree.

       Pursuant   to     Federal     Rule    of     Evidence    701,     lay    opinion

testimony — whether offered by a police officer or a civilian —

must be based on the witness’s personal knowledge.                           See United

States v. Hassan, 742 F.3d 104, 135-36 (4th Cir. 2014).                              The

situation here is similar to that presented in Johnson, where we

determined    that      the   district      court      abused   its    discretion     in

permitting lay opinion testimony of a DEA agent regarding his

interpretation of the defendant’s wiretapped phone calls.                            See

617 F.3d at 293.        Because the agent’s testimony was based on his

“credentials      and     training,      not      his    observations        from    the

surveillance employed in [the] case,” we concluded that “[h]is

post-hoc assessments [could not] be credited as a substitute for

the personal knowledge and perception required under Rule 701.”

Id.    We underscored that, “to adequately build a foundation for

lay testimony,” the testimony must be “based on the perception

of    the   witness.”         Id.   at   292-93     (internal        quotation      marks

omitted).      Here,     there      similarly     is    no   doubt    that    Detective

Helms’s testimony as to the slang terminology was not based on

his observations from the recorded phone calls, but rather on



                                          18
his general experience as a police officer.                            Accordingly, his

testimony was not properly admitted under Rule 701.

     Nevertheless,       in    light      of    the    ample      additional    evidence

linking Stacks to the firearm recovered from Westpark Drive, the

district    court’s    error     was      harmless.          As   we   have   explained,

“when reviewing a nonconstitutional error under Rule 52(a), an

appellate    court     must   determine         if    the    Government       has   proved

‘with     fair   assurance       . . .         that     the       judgment      was    not

substantially swayed by the error.’”                   United States v. Curbelo,

343 F.3d 273, 286 (4th Cir. 2003) (quoting Kotteakos v. United

States, 328 U.S. 750, 765 (1946)).

     In     addition    to     the     temporal        and     geographic      proximity

between the traffic stop and the discovery of the firearm, the

jail calls included numerous references, both veiled and non, to

Stacks possessing and disposing of a firearm after the March 18

traffic stop.        No expert testimony was necessary to explain or

interpret those calls; that Stacks was referring to a firearm

would be obvious to any lay person who heard the recordings.

Indeed,    Stacks     conceded       as   much       when    he   argued      before   the

district court that “words like ‘burner’ and ‘iron’ are commonly

used in popular culture, and it would not assist the jury for a

witness to opine on their meaning.”                   J.A. 276.        Given the common

understanding of those terms, we are readily able to conclude —



                                           19
with fair assurance — that the jury was not substantially swayed

by the admission of Detective Helms’s testimony. 7



                               III.

     Pursuant to the foregoing, we reject Stacks’s contentions

of error and affirm the judgment of conviction.


                                                        AFFIRMED




     7
       Because there was substantial evidence in the record from
which a juror could have found that Stacks was in possession of
a firearm on March 18, 2011, we need not address the
government’s position that Detective Helms could have been
qualified as an expert witness under Federal Rule of Evidence
702.   While Helms, as a veteran officer of thirteen years of
experience, may well possess sufficient credentials to satisfy
Rule 702, the district court explicitly declined to qualify him
as an expert in this case. That the court could have done so is
of no matter in our harmlessness analysis.



                                20
