 United States Court of Appeals
         FOR THE DISTRICT OF COLUMBIA CIRCUIT



Argued April 10, 2018               Decided August 17, 2018

                        No. 15-3040

                UNITED STATES OF AMERICA,
                        APPELLEE

                              v.

   NOE MACHADO-ERAZO, ALSO KNOWN AS GALLO, ALSO
         KNOWN AS NOE MARCHADO-ERAZO,
                   APPELLANT


            Consolidated with 15-3041, 15-3043


        Appeals from the United States District Court
                for the District of Columbia
                    (No. 1:10-cr-00256-8)
                    (No. 1:10-cr-00256-9)
                   (No. 1:10-cr-00256-20)


     Kira Anne West, Christine Pembroke, Marc Eisenstein,
and Thomas G. Corcoran Jr., all appointed by the court, argued
the causes for Appellants. With them on the joint briefs was
Barry Coburn, appointed by the court.

    Elizabeth Gabriel, Assistant U.S. Attorney, U.S.
Attorney’s Office, argued the cause for Appellee. With her on
                              2
the brief were Jessie K. Liu, U.S. Attorney, and Elizabeth
Trosman and John P. Mannarino, Assistant U.S. Attorneys.

    Before: ROGERS, WILKINS and KATSAS, Circuit Judges.

    Opinion for the Court filed by Circuit Judge WILKINS.

    Concurring opinion filed by Circuit Judge ROGERS.

     WILKINS, Circuit Judge: Appellants – Yester Ayala (aka
“Freeway” or “Daddy Yankee”), Noe Machado-Erazo (aka
“Gallo”), and Jose Martinez-Amaya (aka “Crimen” or
“Mecri”) – were charged with conspiracy to violate the
Racketeer Influenced and Corrupt Organizations (“RICO”)
statute, in violation of 18 U.S.C. § 1962(d), and various other
crimes. After a three-week trial, the jury returned guilty
verdicts as to all three Appellants.

    The District Court sentenced Machado-Erazo and
Martinez-Amaya to concurrent terms of life imprisonment for
RICO conspiracy and murder in aid of racketeering, and to 10
years’ consecutive imprisonment for possession of a firearm
during and in relation to a crime of violence. Ayala was
sentenced to concurrent terms of imprisonment for 20 years for
RICO conspiracy and 30 years each for the remaining counts,
and concurrent terms of five years of supervised release for
each D.C. murder count.

     Appellants now challenge their convictions and sentences
on various grounds. Because we find none of Appellants’
challenges persuasive, we affirm.
                               3
                               I.

                               A.

     According to the evidence presented at trial, Appellants
were members of MS-13, a transnational gang founded in El
Salvador. At the time, MS-13 used a hierarchical structure.
The principal leaders of the gang, known as “la Ranflas,” are
located in El Salvador. The second level of the hierarchy,
“programs,” function as collections of the lowest rung of the
hierarchy, local “suborganization[s]” or “cell[s]” known as
“cliques.” While Appellants were involved with MS-13, the
cliques convened regular meetings at which members paid
dues and discussed clique activities. The cliques also obtained
funding by collecting “taxes” (“renta”) from certain entities
within their respective territories. Each clique had two leaders,
the primary leader, who had the “first word” (“primera
palabra”), and the secondary leader, who had the “second
word” (“segunda palabra”). Within a clique, MS-13 members
were assigned specific roles, including “recruiter,”
“extortionist,” “keep[er] [of] weapons,” and treasurer. Groups
of cliques comprised “programs,” which were run by the
gang’s leadership in El Salvador (the “Ranfla”).

     Members of MS-13 marked their territory with graffiti,
used hand signals to identify themselves, and tattooed their
bodies with gang symbols. Gang members were expected to
abide by strictly enforced “rules” that mandated attendance at
regularly scheduled clique meetings, the payment of dues, the
refusal to cooperate with law enforcement, and the murder of
rival gang members (“chavalas”). Members who failed to
follow these rules were subjected to physical punishment or
death. MS-13’s leaders authorized the killing of a recalcitrant
member by issuing a “green light,” which other gang members
                               4
were expected to execute when possible or face punishment or
death themselves.

     At trial, the Government presented evidence that
Machado-Erazo and Martinez-Amaya were members of the
Normandie clique in the D.C. area, and that both had leadership
roles. Machado-Erazo helped financially support the clique
through drug dealing and the extortion of local brothels and
other drug dealers. Moises Humberto Rivera-Luna (aka “Viejo
Santos”), who oversaw MS-13’s activities in the Washington,
D.C. area despite being incarcerated in El Salvador, called on
Machado-Erazo to “improve the [Normandie] clique.” J.A.
1603-04. Machado-Erazo worked with one of the clique’s
leaders, Jorge Solorzano, to achieve this goal. Machado-Erazo
was also one of the leaders of “La Hermandad,” a program of
local cliques with the purpose of “clean[ing] up the cliques” by
“kill[ing] . . . the snitches.” J.A. 1395, 1617-18, 1739.

      Martinez-Amaya was sent from El Salvador to assist the
Normandie clique when Dennis Gil-Bernardez (aka “Pando”),
its longtime leader, was arrested in December 2008. J.A. 1082
(stating that Pando was arrested in December 2008), 1244
(stating that Martinez-Amaya (aka “Crimen”) was sent to D.C.
after Pando was arrested). Martinez-Amaya served as
second-in-command to Solorzano, and when Solorzano was
arrested, Martinez-Amaya became the clique leader.

     The Government separately presented evidence that Ayala
was a member of the Sailors clique, another clique in the D.C.
area, and was one of its leaders in 2008.

                              B.

   By superseding indictment filed on May 9, 2013,
Appellants and four co-conspirators were charged with
                               5
conspiracy to violate the RICO statute, in violation of 18
U.S.C. § 1962(d). Ayala was also charged with two counts of
murder in aid of racketeering (“VICAR murder”), in violation
of 18 U.S.C. § 1959(a)(1), and two counts of first-degree
murder while armed, in violation of D.C. Code §§ 22-2101 and
22-4502. In addition to the RICO conspiracy charge,
Machado-Erazo and Martinez-Amaya were charged with one
count each of VICAR murder and possession of a firearm
during and in relation to a crime of violence, in violation of 18
U.S.C. § 924(c)(1)(A).

     Appellants’ trial lasted from June 18, 2013, to August 6,
2013. Presentation of evidence lasted approximately fourteen
court days, and the jury deliberated for eleven days. The
parties called approximately fifty witnesses and introduced
over two hundred exhibits. United States v. Machado-Erazo, 986
F. Supp. 2d 39, 43 (D.D.C. 2013). Among the government’s
evidence were testimony of co-conspirators regarding MS-13
activities in the D.C. area, consensual recordings of MS-13
meetings, and wiretaps of calls among MS-13 members,
including the three defendants. Id.

     The jury returned verdicts of guilty as to all three
defendants. Machado-Erazo and Martinez-Amaya were found
guilty of (1) violating RICO, (2) VICAR murder, and (3)
possession of a firearm during and in relation to a crime of
violence. The jury answered the special finding in the
affirmative, determining that both defendants “did feloniously,
willfully, and of deliberately premeditated malice aforethought
kill and murder Felipe Leonardo Enriquez.” J.A. 709, 711.
The jury also found that the pattern of racketeering activity
agreed to included (i) murder in violation of the D.C. Code or
Maryland law; (ii) extortion in violation of the D.C. Code or
Maryland law; and (iii) obstruction of justice. The jury found,
however, that the pattern of racketeering activity did not
                               6
include robbery, violation of federal narcotics laws, or witness
retaliation or tampering. J.A. 708-09, 710-11.

     Ayala was also convicted of participating in the same
RICO conspiracy. The jury found that Ayala agreed to the
same three racketeering activities, and returned guilty verdicts
against Ayala as to two counts of VICAR murder and two
counts of murder under the D.C. Code deriving from the
killings of Luis Alberto Membreno-Zelaya on or about
November 6, 2008, and of Giovanni Sanchez on or about
December 12, 2008. J.A. 712-15.

     After the jury rendered its verdict, Machado-Erazo and
Martinez-Amaya filed timely renewed motions for judgment of
acquittal and for a new trial based on the insufficiency of the
evidence, as well as on other grounds not relevant here. The
District Court denied both motions. See Machado-Erazo, 986
F. Supp. 2d at 57. Subsequently, the District Court sentenced
Machado-Erazo and Martinez-Amaya to concurrent terms of
life imprisonment for RICO conspiracy and VICAR murder,
and to 10 years’ consecutive imprisonment for possession of a
firearm during and in relation to a crime of violence. The court
sentenced Ayala to concurrent terms of imprisonment for 20
years for RICO conspiracy and 30 years each for the remaining
counts, and concurrent terms of five years of supervised release
for each D.C. murder count.

    Appellants now challenge their convictions and sentences
on various grounds. We consider Appellants’ claims that other
crimes evidence was improperly admitted in part II, their
claims that cell-site data was improperly admitted in part III,
and their other claims in an unpublished judgment issued
herewith.
                                7
                               II.

    Appellants challenge the admission under Federal Rules
of Evidence 404(b) and 403 of the following acts of violence
perpetrated by co-conspirators: (1) the July 29, 2008, murder
of Luis Chavez-Ponce by Gil-Bernardez; (2) the October 6,
2008, shooting of Malcom Wilson, David Cook, and Dalton
Beck by Gill-Bernardez; (3) August and September 2008
shootings in Sterling, Virginia; (4) the October 16, 2009, armed
gang fight in Wheaton, Maryland; and (5) the December 9,
2009, shooting of Glorisnel Sorto by Mario Lopez-Ramirez.

     Appellants argue that the Government did not tie this
evidence to Appellants, and as such, the testimony with respect
to these incidents, as well as photographs of the crime scenes,
were not relevant and were unduly prejudicial. Appellants’ Br.
36-37. Appellants assert that the “evidence was nothing more
than evidence of bad character, or guilt by association, intended
to sway the jury,” and make the jury believe “that appellants
would likely have committed the acts . . . alleged[.]” Id. at 37.
The Government, however, argues that admitting this evidence
was not in error because these crimes, some of which were
charged as overt acts, were direct proof of the conspiracy, and
thus were not subject to exclusion under Federal Rule of
Evidence 404(b). Appellee’s Br. 26-27. The Government has
the stronger position here, and we hold that the District Court
did not abuse its discretion in allowing this evidence.

                               A.

     Below is a summary of the challenged evidence.1 None of
the three Appellants was present during any of these incidents,

1
 In reply, Appellants suggest that they object to the admission of
additional evidence not specified in their opening brief. Reply 2.
                                  8
but each of the incidents involved members of the Normandie
clique, of which Machado-Erazo and Martinez-Amaya were
members. And, as discussed further below, the evidence
showed a close connection between the Normandie clique and
the Sailors clique, of which Ayala was a member.

     Murder of Luis Chavez-Ponce. At trial, co-conspirator
Antonio Urrutia-Barrera, a member of the Normandie clique,
testified that he was with Tokiro Rodas-Ramirez,
Gil-Bernardez, then clique leader, and other members of the
clique at an apartment complex in Riverdale, Maryland on July
29, 2008, when they spotted Chavez-Ponce, a rival gang
member, riding a bicycle around the complex. J.A. 1227-29,
1342; Appellee’s Br. 20-21. According to Urrutia-Barrera,
Gil-Bernardez shot Chavez-Ponce. J.A. 1229.

     Shootings of Malcom Wilson, David Cook, and Dalton
Beck. Urrutia-Barrera also testified to the shooting of Wilson,
Cook, and Beck that occurred in October 2008. According to
Urrutia-Barrera, he, Gil-Bernardez, and other members of the
Normandie clique were in a car in Reston, Virginia, when they
saw rival gang members Wilson, Cook, and Beck in another
car flashing gang signs. J.A. 1238-39; Appellee’s Br. 21. The
clique members went to one of their apartments, Gil-Bernardez

We decline to consider any arguments not specifically discussed in
their opening brief, however. Fed. R. App. P. 28(a)(8)(A); see, e.g.,
United States v. Golliher, 820 F.3d 979, 984-85 (8th Cir. 2016) (“We
may . . . refuse to consider a challenge to a district court’s decision
to exclude evidence when the appellant fails to direct us to the part
of the record that contains the substance of the excluded evidence,
especially when the substance is necessary to evaluate admissibility
under the Federal Rules of Evidence.”); Guillemard-Ginorio v.
Contreras-Gomez, 585 F.3d 508, 534 (1st Cir. 2009) (holding that
evidentiary challenges were waived due to failure to cite “relevant
portions of the appendix or transcript”).
                               9
grabbed his backpack, and then they went looking for the three
rival gang members. J.A. 1240. Urrutia-Barrera testified that
once they found Wilson, Cook, and Beck, they parked the car
and started walking toward them, and Gil-Bernardez shot at
them J.A. 1240-41. Urrutia-Barrera testified that the gun
Gil-Bernardez used was the same one used in the Riverdale,
Maryland shooting. J.A. 1242. A victim of the shooting also
testified to the incident during trial. J.A. 1212-15.

     Shootings in Sterling, Virginia. Urrutia-Barrera testified
about two shootings that occurred in August and September
2008, in Sterling, Virginia. J.A. 1236. On cross-examination,
with respect to the first shooting, he testified that he was with
two other MS-13 members, looking for rival gang members.
J.A. 1253. When they found the chavalas, Urrutia-Barrera shot
them. Id. Urrutia-Barrera testified that he shot the chavalas on
Gil-Bernardez’s instruction. J.A. 1254.

     Armed Gang Fight on October 16, 2009. Special Agent
Brendan Shelley and co-conspirator Manuel Saravia, a member
of the Normandie clique, testified regarding a fight between
MS-13 members and a group of individuals that occurred on
October 16, 2009, in Wheaton, Maryland. J.A. 1331-34,
1429-30. The MS-13 members were armed with bolt cutters
and other weapons. J.A. 1429-30. The fight broke up when
law enforcement arrived. J.A. 1334-35, 1430.

     Shooting of Glorisnel Sorto. Saravia testified that he and
co-conspirator Lopez-Ramirez, also a member of the Normandie
clique, shot Sorto, a rival gang member, on December 9, 2009,
in Washington, D.C. J.A. 1430-37; see also J.A. 1351-53
(testimony of a Government witness regarding the incident).
The Normandie clique reimbursed the price of the gun used in
the shooting. J.A. 1433.
                               10
    None of the witnesses linked any of the incidents to any
specific defendant, but all involved the Normandie clique.

                               B.

     As a preliminary matter, the parties dispute the standard of
review the Court is to apply. Appellants urge this Court to
review their challenges to the admission of this evidence for an
abuse of discretion. Appellants’ Br. 34. Appellee, however,
contends that this standard applies only to objections that have
been preserved, and argue that Appellants preserved their
objections only as to the Chavez-Ponce murder and the Reston
triple shooting. Appellee’s Br. 25-26. Accordingly, the
Government states that the Court should review the admission
of the evidence regarding the Chavez-Ponce murder and the
Reston triple shooting for abuse of discretion, but apply the
plain-error standard to the admission of the other evidence. Id.
Appellants maintain that they “persistently objected” to the
admission of the challenged testimony. Appellants’ Br. 36
n.28.

      Appellants are correct; at various times before and during
trial, Appellants objected to the evidence summarized above,
as well as other similar evidence, on the grounds that it was
irrelevant and/or unduly prejudicial.2 See, e.g., J.A. 954-58
(denying Machado-Erazo’s and Martinez-Amaya’s motion to
exclude any Rule 404(b) evidence), 1211-12 (objecting to the
introduction of testimony regarding the Reston triple shooting),
1488-89 (objecting to testimony regarding the Sorto shooting),
1342-43 (objecting to evidence related to the murder of

2
  The District Court ruled that all defendants would be deemed to
join any motion or objection made by a co-defendant during trial.
J.A. 80. Accordingly, who made the objection is irrelevant for our
purposes.
                              11
Chavez-Ponce); United States v. Ayala, No. 10-cr-256, ECF
No. 342 (D.D.C. filed May 21, 2013) (motion to exclude co-
conspirators’ statements); United States v. Flores, No. 10-cr-
256, ECF No. 165 (D.D.C. filed May 10, 2012) (motion to
exclude irrelevant and prejudicial gang evidence); United
States v. Machado-Erazo, No. 10-cr-256, ECF No. 143
(D.D.C. filed May 5, 2012) (motion in limine to preclude
admission of co-conspirators’ evidence). Accordingly, we
review the admission of the evidence for abuse of discretion.
United States v. Johnson, 519 F.3d 478, 483 (D.C. Cir. 2008).

                              C.

     Rule 404(b) provides that “[e]vidence of a crime, wrong,
or other act is not admissible to prove a person’s character in
order to show that on a particular occasion the person acted in
accordance with the character.” Fed. R. Evid. 404(b)(1). Yet
the rule permits such evidence for other purposes, including
proof of motive, intent, knowledge, identity and absence of
mistake. Fed. R. Evid. 404(b)(2). Indeed, “Rule 404(b) is a
rule of inclusion rather than exclusion,” United States v.
Bowie, 232 F.3d 923, 929 (D.C. Cir. 2000), “prohibiting the
admission of other crimes evidence ‘in but one circumstance’
– for the purpose of proving that a person’s actions conformed
to his character,” United States v. Crowder, 141 F.3d 1202,
1206 (D.C. Cir. 1998) (en banc) (quoting United States v.
Jenkins, 928 F.2d 1175, 1180 (D.C. Cir. 1991)). “Rule 404(b)
thus is not so much a character rule as a special aspect of
relevance” because it “does not prohibit character evidence
generally, only that which lacks any purpose but proving
character.” Bowie, 232 F.3d at 930.

    Thus, a threshold question in determining the admissibility
of evidence of other crimes and bad acts is whether the
evidence, in actuality, relates to acts unconnected with those
                               12
for which the defendant is charged, or instead is intertwined
with the commission of charged crimes. Acts “extrinsic” to the
crime charged are subject to Rule 404(b)’s limitations; acts
“intrinsic” to the crime are not. See Bowie, 232 F.3d at
927; see also United States v. Mahdi, 598 F.3d 883, 891 (D.C.
Cir. 2010).

     In conspiracy prosecutions, the prosecution is “usually
allowed considerable leeway in offering evidence of other
offenses ‘to inform the jury of the background of the
conspiracy charged . . . and to help explain to the jury how the
illegal relationship between the participants in the crime
developed.’” United States v. Mathis, 216 F.3d 18, 26 (D.C.
Cir. 2000) (quoting United States v. Williams, 205 F.3d 23,
33-34 (2d Cir. 2000)). In addition, “where the incident offered
is a part of the conspiracy alleged[,] the evidence is admissible
under Rule 404(b) because it is not an ‘other’ crime.” United
States v. Hemphill, 514 F.3d 1350, 1357 (D.C. Cir. 2008)
(quoting United States v. Mejia, 448 F.3d 436, 447 (D.C. Cir.
2006)). This Court has also permitted the introduction of
“other acts” evidence in conspiracy cases to link a defendant to
other defendants and drug transactions for which the
conspiracy was responsible, United States v. Gaviria, 116 F.3d
1498, 1532 (D.C. Cir. 1997) (per curiam); to show the nature
of a conspiracy and “the kind of organizational control” a
defendant exercised, Mahdi, 598 F.3d at 891; and to show the
defendants’ intent to act in concert, Mathis, 216 F.3d at 26; see
also United States v. Straker, 800 F.3d 570, 590 (D.C. Cir.
2015) (per curiam) (evidence of uncharged hostage takings was
“relevant to . . . how those defendants started to work together
as kidnappers”).

    The Government contends that because the conspiracy
was defined as MS-13 more generally, and MS-13 activities in
the United States extend back to the late 1990s, evidence of
                              13
MS-13 activity anywhere is admissible under Rule 404(b),
subject only to Rule 403’s limitations. Oral Arg. 58:10-59:25.
Fortunately, we need not decide whether the Government’s
capacious determination of how a conspiracy can be defined
and how it relates to Rule 404(b) is correct because under this
Court’s precedent and the definition of the conspiracy here, the
challenged acts were intrinsic evidence of the RICO conspiracy
– the evidence helped prove the nature of the conspiracy and
the purpose of the enterprise. J.A. 125 (defining the conspiracy
as all of the illicit activities of members of MS-13 in the
District of Columbia (“La Hermandad”)). Indeed, three of the
purported other crimes – the Chavez-Ponce murder, the Reston
triple shooting, and the Sorto shooting – were specifically
charged in the indictment as overt acts of the conspiracy, see
J.A. 131-33, and therefore do not constitute “other crimes,” see
United States v. McGill, 815 F.3d 846, 879 (D.C. Cir. 2016)
(per curiam).

     Moreover, the challenged acts and the acts in which
defendants were alleged to have actively participated are in
close temporal proximity. The timeframe for the challenged
acts spans July 2008 through December 2009. The evidence,
taken in the light most favorable to the Government, shows that
Machado-Erazo and Martinez-Amaya were members of the
Normandie clique by at least December 2008. J.A. 1082
(Solorzano (aka “Cocky”) became clique leader when
Gil-Bernardez (aka “Pando”) was arrested in December 2008),
1736-37 (Avila testified he knew Machado-Erazo from at least
when Cocky took over the clique), 1244 (Martinez-Amaya
(aka “Crimen”) was sent to the area when Gil-Bernardez was
arrested), 1598 (Martinez-Amaya was part of the clique before
Solorzano became leader). The evidence also shows that Ayala
was the leader of the Sailors clique in 2008. J.A. 1179, 1121,
1110. The evidence also showed that the Sailors and
Normandies worked together to further the goals of MS-13.
                               14
See, e.g., J.A. 1079 (discussing cooperation between Sailors and
Normandies), 1085 (Sailors attended a Normandie clique
meeting), 1111-12 (Sailors and Normandies were in contact
with each other), 1117-18 (if one clique put a green light on
someone, members of other cliques were obligated to act on
the green light), 1724-28 (Sailors and Normandies fought
together). “[W]here the incident[s] offered [are] part of the
conspiracy alleged . . . the evidence is admissible under Rule
404(b) because it is not an ‘other’ crime.” Mejia, 448 F.3d at
447; Bowie, 232 F.3d at 929.

     The determination that this evidence does not constitute
impermissible character evidence does not end the inquiry.
Once a defendant raises a 404(b) objection, the district court
must balance the probative value of the evidence against the
risk of unfair prejudice. McGill, 815 F.3d at 883; United States
v. Lavelle, 751 F.2d 1266, 1279 (D.C. Cir. 1985) (requiring a
district court “to make an on-the-record determination” of
whether the probative value of other-bad-acts evidence
outweighs its prejudicial impact”). The District Court did not
explicitly do so here, and this failure is particularly concerning
where, as discussed above, the Government takes the broad
position that evidence regarding MS-13 activity anywhere in
the United States since the 1980s is admissible under Rule
404(b). The Government’s position highlights the importance
of the district court performing the requisite Rule 403
balancing on the record.

    Nevertheless, because “the factors upon which the
probative value/prejudice evaluations were made are readily
apparent from the record, and there is no substantial
uncertainty about the correctness of the ruling,” reversal is not
required. McGill, 815 F.3d at 883 (citation and quotation
marks omitted). The evidence here related solely to acts
involving the Normandie and Sailors cliques and only during
                              15
time periods where one or more defendants were active in the
cliques. Indeed, comparable other evidence was presented
showing Appellants’ involvement in other acts of violence
committed by the gang, including: testimony connecting Ayala
with the murders of Louis Membreno-Zelaya and Giovanni
Sanchez, J.A. 1044-49, 1171, 1267-82, 1329-30, and
Machado-Erazo and Martinez-Amaya with the murder of
Felipe Enriquez, J.A. 1397-1404, 1476-77. Other evidence
showed that murder, both threatened and actualized, is central
to MS-13’s control over its members and its ability to
intimidate non-members. See, e.g., J.A. 989-92, 1616, 1738,
1741, 1795. This evidence “dissipate[d] any prejudice
associated” with the challenged evidence. McGill, 815 F.3d at
884.

     Accordingly, we conclude that the District Court did not
abuse its discretion by allowing the admission of the
challenged evidence.

                             III.

     Machado-Erazo and Martinez-Amaya also challenge the
testimony of the Government’s cell-site expert, FBI Special
Agent David Magnuson. Magnuson’s testimony was offered
to show that the cell phones used by Machado-Erazo,
Martinez-Amaya, and a cooperating witness were in the
vicinity of the remote area where the body of Felipe Enriquez
was found on or about March 28, 2010, the date Enriquez was
believed to have been killed. United States v. Machado-Erazo,
950 F. Supp. 2d 49, 51 (D.D.C. 2013). Magnuson’s report
depicted the geographic location of the cell towers used by the
phones and analyzed the phones as they moved through the
Cricket and T-Mobile cellular networks. Id.
                               16
     Appellants contend that the District Court erred by
allowing Magnuson’s testimony because the Government
deviated from its initial notice regarding Magnuson’s
testimony by proffering opinions about specific distances
rather than broad ranges, Magnuson’s testimony exceeded the
bounds of his expertise, and the Government’s subsequent
notice regarding specific location testimony was untimely. We
review for abuse of discretion a district court’s evidentiary
rulings concerning the admission of expert testimony. United
States v. Day, 524 F.3d 1361, 1369 (D.C. Cir. 2008) (citing
Kumho Tire Co. v. Carmichael, 526 U.S. 137, 152 (1999)).
However, “[e]ven when the [D]istrict [C]ourt has abused its
discretion, reversal is appropriate only upon a concomitant
finding that the error affected appellant’s ‘substantial rights.’”
See English v. Dist. of Columbia, 651 F.3d 1, 7 (D.C. Cir. 2011)
(citation omitted); see also Kotteakos v. United States, 328
U.S. 750, 764-65 (1946).

     For the reasons discussed below, we find that the District
Court abused its discretion by allowing Agent Magnuson to
testify regarding specific distances and ranges of distances
because such testimony was neither disclosed pursuant to
Federal Rule of Criminal Procedure 16, nor vetted as required
by Federal Rules of Evidence 702 and 403. Nevertheless,
because the error was harmless, reversal is not warranted.

                               A.

     Before submitting their joint pretrial statement, the
Government provided notice, see Fed. R. Crim. P. 16(a)(1)(G),
that it intended to call Magnuson as an expert in cellular
technology and the analysis of historical cellular telephone and
cell site records. The Government also produced a copy of
Magnuson’s report – a series of maps with annotations but little
explanatory text – which it contended showed the activity of
                               17
cell phones used by Machado-Erazo, Martinez-Amaya, and
Saravia on the day of the Enriquez murder.

     Approximately one week before trial, Machado-Erazo
moved to exclude Agent Magnuson’s testimony, arguing that
the testimony was not based on a sufficiently reliable
methodology as required by Rule 702 and that it would
therefore be unduly prejudicial and excludable pursuant to
Rule 403. See generally Machado-Erazo, 950 F. Supp. 2d 49.
The Government opposed Machado-Erazo’s motion, and
asserted that Magnuson was a highly trained agent whose
testimony was firmly based in scientific principles. The
Government emphasized that Magnuson would not claim to
have determined the exact location of the phone user, but rather
the general location where a cell phone would have to be
located to use a particular cell tower and sector. Government’s
Opposition to Defendant’s Motion in Limine to Exclude Expert
Testimony and Cellular Report of FBI Special Agent David
Magnuson, United States v. Machado-Erazo, No. 10-cr-256,
ECF No. 368 (D.D.C. filed June 12, 2013).

     The District Court denied Machado-Erazo’s motion in
limine. See generally Machado-Erazo, 950 F. Supp. 2d 49. In
addition to rejecting Appellants’ “fundamentally erroneous
contention . . . that a cell phone always connects to the closest
tower at the time a call is placed,” the District Court determined
that “th[e] methodology employed by [ ] Magnuson clears the
hurdle imposed by Daubert and [Federal Rule of Evidence]
702.” Id. at 55, 56. The District Court relied on United States
v. Jones, 918 F. Supp. 2d 1 (D.D.C. 2013) (rejecting similar
arguments on a motion to exclude cell-site analysis), and
United States v. Davis, No. 11-60285-CR, 2013 WL 2156659
(S.D. Fla. May 17, 2013) (permitting Magnuson to offer the
                                 18
exact same type of testimony offered here after a Daubert
hearing).3

     During trial, which occurred before a different district
judge, Machado-Erazo renewed his objection based on Rule
702. He also argued that the government failed to timely
disclose that Magnuson would estimate a coverage range for
the cell towers. J.A. 1497-98. The Government responded that
the purported disclosure merely “describe[d] how [Magnuson]
went about making his report,” and emphasized that Magnuson
would discuss only the “general range of the cell towers,” not
the specific location of a person, which was already endorsed
by the District Court. Id. at 1498-99. The District Court
overruled Machado-Erazo’s objection, and permitted
Magnuson to testify.

                                 B.

     Notwithstanding the Government’s representation to the
District Court, the Government elicited testimony from
Magnuson about precise locations of the cell phones he
analyzed. See J.A. 1497-98 (testifying to “a coverage range for
the cell towers”), 1518-19 (testifying that the two phones were
“very close” to a particular cell tower at the time of the
murder), 1520 (testifying that that the phones were within “a
half mile of th[e] tower” at the time of the murder), 1532-33
(testimony regarding the “proximity between th[e] two
phones” at the time of the murder). Appellants contend that

3
  Appellants do not challenge the District Court’s denial of the
pretrial motion in limine. Instead, they claim only that the specific
location testimony offered at trial exceeded the Government’s
proffer and Magnuson’s expertise. Oral Arg. 5:36-6:20 (conceding
that their concern was not with the general methodology of collecting
and interpreting cell-site data, but rather with the specific location
testimony).
                                19
admission of this testimony constituted an abuse of discretion.
We agree.

      Under Federal Rule of Criminal Procedure 16(a)(1)(G),
“the government must give to the defendant a written summary
of any testimony that the government intends to use under
Rule[] 702 . . . during its case-in-chief at trial. The summary
. . . must describe the witness’s opinions, the bases and reasons
for those opinions, and the witness’s qualifications.” The
Government provided no such disclosure here. Indeed, the
only summary provided pre-trial was a series of slides showing
the location of cell towers and the cell sector for particular calls
without explanation. J.A. 284-321. The briefing on the motion
in limine did little to clarify the scope of Agent Magnuson’s
testimony, noting only that “[the] proposed testimony will not
claim to have determined the exact location of the phone user,”
J.A. 639 n.1. The Government’s disclosure and statements,
then, left both the District Court and the parties to presume
what the testimony would be. This, in and of itself, shows that
the notice was deficient under Rule 16. Nevertheless, based
upon a reported decision admitting Magnuson’s testimony in
another jurisdiction, as well as other decisions admitting other
cell-site expert testimony, the District Court inferred the bases
and reasons underlying Magnuson’s opinions and denied the
motion in limine. Machado-Erazo, 950 F. Supp. 2d at 53-58.
Critically, the ruling was based upon the understanding that
Magnuson would offer testimony about only the “general
location” of cell phones, rather than precise locations. Id. At
trial, before a different judge, the Government shifted gears and
elicited testimony about more precise locations. By admitting
this expert testimony without giving defendants sufficient prior
notice and without first finding it to be relevant and reliable
under Daubert, the District Court abused its discretion. See
Estate of Barabin v. AstenJohnson, Inc., 740 F.3d 457, 464 (9th
Cir. 2014) (en banc).
                                20

     That the District Court abused its discretion does not end
the inquiry, as “reversal is appropriate only upon a concomitant
finding that the error affected appellant’s ‘substantial rights.’”
See English, 651 F.3d at 7 (citation omitted). An error affects
the appellant’s substantial rights if it influenced or tainted the
outcome of the district court proceedings. United States v.
Olano, 507 U.S. 725, 734 (1993); United States v. Smith, 232
F.3d 236, 243 (D.C. Cir. 2000). As the Supreme Court noted
in Kotteakos, “[t]he inquiry cannot be merely whether there
was enough to support the result, apart from the phase affected
by the error. It is rather, even so, whether the error itself had
substantial influence. If so, or if one is left in grave doubt, the
conviction cannot stand.” 328 U.S. at 765. Where the Court is
sure “that the error did not influence the jury, or had but very
slight effect, the verdict and the judgment should
stand.” Id. Magnuson’s expert testimony related solely to the
murder of Felipe Enriquez. Given the breadth of evidence
linking Machado-Erazo and Martinez–Amaya to the murder,
much of which was undisputed, we find that admission of the
challenged testimony was not prejudicial, and therefore
reversal is not appropriate.

     At trial, the Government presented the following
undisputed and unchallenged evidence. First, Saravia, the
Government’s key witness, testified that during a clique
meeting on March 6, 2010, Enriquez (aka “Zombie”)
disrespected Solorzano (aka “Cocky”), then-leader of the
Normandie clique, and brought a knife to the meeting, which
violated MS-13 rules. J.A. 1397-99. The Government
submitted an audio recording of the clique meeting
corroborating this testimony. See J.A. 826-877, 1737. This
evidence provided the motive for the murder. Second, the
Government presented wiretaps of a phone call during which
Solorzano, Machado-Erazo, and Saravia discussed Enriquez’s
                              21
behavior and agreed to call Rivera-Luna (aka “Viejo Santos”),
who oversaw MS-13’s activities in the Washington, D.C. area
from an El Salvadorian jail, as well as a phone conversation
during which Viejo Santos put a green light on Enriquez. J.A.
1744. Third, the location of the murder is undisputed. During
trial, a detective testified that Enriquez’s body was discovered
in a wooded area off Ednor Road, near the Patuxent River, J.A.
1382-84, 1491, 1494, and that police recovered eight
9-millimeter cartridge casings near his body, J.A. 1387. Agent
Magnuson’s testimony further showed that phones linked to
Saravia, Machado-Erazo, and Martinez-Amaya were
connected to cell towers located nearest to the murder site at
approximately the same time or close in time to each other.
J.A. 1512-34. His permissible testimony also showed that
phones linked to Machado-Erazo and Saravia were connected
to the cell tower closest to Machado-Erazo’s home prior to the
time that the three phones were connected to the towers near
where the murder occurred. Thus, Magnuson’s permissible
testimony corroborated Saravia’s testimony that he and
Machado-Erazo met before the murder and drove to the site of
the murder together. J.A. 1402-16. Given this evidence, we
cannot say that the District Court’s erroneous admission of
portions of Agent Magnuson’s testimony affected Appellants’
“substantial rights.”         We therefore reject Appellants’
contention that their VICAR and firearm convictions should be
reversed based on Magnuson’s improper testimony.

                             ***

    For the foregoing reasons, we affirm.
    ROGERS, Circuit Judge, concurring: I join the court’s
opinion holding that the district court abused its discretion by
allowing Agent Magnuson to testify as an expert witness
regarding specific cell tower distances and ranges of distances.
I write briefly on the relationship between the district court’s
“gatekeeping” obligation under Federal Rule of Evidence 702
and the government’s disclosure obligations upon defense
request under Federal Rule of Criminal Procedure 16(a)(1)(G).

                               I.

    A witness may testify as an expert only if

         (a) the expert’s scientific, technical, or other
         specialized knowledge will help the trier of fact to
         understand the evidence or to determine a fact in
         issue; (b) the testimony is based on sufficient facts or
         data; (c) the testimony is the product of reliable
         principles and methods; and (d) the expert has reliably
         applied the principles and methods to the facts of the
         case.

FED. R. EVID. 702. The district court must serve as a gatekeeper
to the admission of expert testimony. Daubert v. Merrell Dow
Pharm., Inc., 509 U.S. 579, 597 (1993). Although perhaps
originally spawned by concerns about “junk science”
masquerading as science, see Gen. Elec. Co. v. Joiner, 522 U.S.
136, 153 (1997) (Breyer, J., concurring), the “gatekeeper role”
ensures more broadly that witnesses possess the relevant
training or experience in the field of expertise on which they
will testify, and that, if found qualified, their testimony stays
within the realm of their expertise. “[T]o ensure the reliability
and relevancy of expert testimony,” Kumho Tire Co., Ltd. v.
Carmichael, 526 U.S. 137, 152 (1999), the district court has a
threshold obligation to independently determine whether and to
what extent a witness can testify as an expert, as well as a
continuing responsibility to ensure, upon defense objection,
                                2
that the expert’s testimony stays within permissible bounds.
The heightened aura and weight to which a fact finder is likely
to attach to expert testimony, as compared to lay testimony, cf.
United States v. Williams, 827 F.3d 1134, 1160-61 (D.C. Cir.
2016), warrants the two-part nature of the gatekeeper role.

     The district court’s ability to fulfill its gatekeeping
obligations is not unrelated to the government’s compliance
with Federal Rule of Criminal Procedure 16. Rule 16 states in
relevant part:

         At the defendant’s request, the government must give
         to the defendant a written summary of any testimony
         that the government intends to use under Rules 702,
         703, or 705 of the Federal Rules of Evidence . . . The
         summary provided under this subparagraph must
         describe the witness’s opinions, the bases and reasons
         for those opinions, and the witness’s qualifications.

FED. R. CRIM. P. 16(a)(1)(G).

     This disclosure mandate is designed to “minimize surprise
that often results from unexpected expert testimony, reduce the
need for continuances, and to provide the opponent with a fair
opportunity to test the merit of the expert’s testimony through
focused cross-examination.” Adv. Comm. Note to 1993
Amendment. Further, prompt notice of a putative expert’s
qualifications “will permit the requesting party to determine
whether in fact the witness is an expert within the definition of
Federal Rule of Evidence 702.” Id. The Rule reflects a trend
toward “freer disclosure” in criminal procedure. 2 CHARLES
ALAN WRIGHT & ARTHUR R. MILLER, FEDERAL PRACTICE &
PROCEDURE § 251 (4th ed. 2018).
                                  3
     The Rule provides the district court with a range of
remedial options: a continuance, exclusion of the evidence, or
“any other order that is just under the circumstances.” FED. R.
CRIM. P. 16(d)(2). The district court’s rulings under Rule 16
and FRE 702 are reviewed for abuse of discretion, United
States v. Day, 524 F.3d 1361, 1367, 1370 (D.C. Cir. 2008), and
an error is harmless if there was no “substantial and injurious
effect or influence in determining the jury’s verdict,” Kotteakos
v. United States, 328 U.S. 750, 776 (1946).

                                 II.

     What is striking in the instant case is how the government’s
failure to disclose promptly its proposed expert’s opinions and
the bases for those opinions can hamstring the district court’s
effort to separate reliable expert testimony from “junk science.”
On June 10, 2011, defense counsel, by letter to the trial
prosecutors, requested “a written summary of any expert
testimony which the government intends to use under Rule[]
702 . . . in its case-in-chief at trial.” The joint pretrial statement
of May 21, 2013, indicated that FBI Special Agent David
Magnuson would testify as an expert in historical cell-site
analysis.        Approximately one month before trial, the
government turned over its expert’s “report.” This consisted of
a series of maps where cell tower locations and angles were
plotted; no “written summary” describing the nature of
Magnuson’s opinion was included.

     Defense counsel moved to exclude Magnuson’s testimony
as an expert, arguing his testimony relied on a methodology
that was “unreliable and irrelevant,” and requested a hearing.

          Agent Magnuson’s report does not describe the bases
          and reasons for his opinions or the inferences he
          draws. See Fed. R. Crim. P. 16(a)(1)(G). The report
                               4
         merely plots the presumed locations from which calls
         were made, the cell tower from which the call
         registered at its origin, and the relation to the crime
         scenes charged in this case. There is no indication
         how these plotted called are placed on the map or what
         determined their placement. The cell towers to which
         certain cell phones connected on a map have been
         used by Agent Magnuson to assume a basic coverage
         area. This is not supported by the facts or record in
         this case.

Def.’s Mot. to Exclude the Expert Testimony and Cellular
Analysis Report and Charts of Special Agent David Magnuson
(June 12, 2013) (“Motion to Exclude”) at 2-3. Further, the
defense argued that if Magnuson “testifies only to the cell
tower location and side of the cell tower antennae that received
the call,” then he will be “acting not as an ‘expert’ but merely
as a summary witness.” Id. at 13. Referencing Magnuson’s
prior expert testimony, the defense also suggested that if
allowed to testify as an expert he “may attempt to go far beyond
this summary testimony.” Id.

     In opposing the Motion to Exclude, the government
represented that Magnuson “will not claim to have determined
the exact location of the phone user, but rather the general
location where a cell phone would have to be located to use a
particular cell tower and sector.” Gov’t Opp’n to Def.’s Mot.
to Exclude Expert Testimony (“Gov’t Opp’n”) (June 12, 2013).
Further, claiming neither a Daubert hearing nor peer review of
the cell-site methodology was needed because it had been
approved by a number of district court judges, the government
also did not describe how Magnuson would use the cell tower
locations in his “report” to project the likely area where a cell
phone was located. The district court denied the defense
motion, relying on the government’s representations,
                               5
Magnuson’s “report,” and prior district court rulings allowing
expert testimony on cell-site analysis. See United States v.
Machado-Erazo, 950 F. Supp. 2d 49, 55-58 (D.D.C. 2013).

     Hours before Magnuson was scheduled to testify on the
eighth day of the trial before a jury, the government turned over
to the defense a document titled “Basic Principals [sic] Utilized
in Record Analysis.” It stated: “As a GENERAL RULE, most
towers (depending on the environment) have a radius of
approximately ONE or TWO MILES (greater or less distances
are also common).” Defense counsel objected to the late
disclosure and requested that Magnuson be treated as a lay
witness. The district court permitted Magnuson to testify as an
expert after the prosecutor represented Magnuson would testify
only “as to the general range of the cell towers” and that the
issue had been ruled on when the Motion to Exclude was
denied. Trial Tr. 25-26 (July 8, 2013). Magnuson testified at
length over two days (91 transcript pages) as an expert at
appellants’ trial. His testimony included a discussion of the
areas where cell phones belonging to appellants and a co-
conspirator were located on the day of Felipe Enriquez’s
murder. Magnuson also testified that a cell phone “had to be
within a half mile” of a particular cell tower for the phone to
connect to that tower. Id. at 51. On that basis, a cell phone
belonging to the co-conspirator was located near Machado-
Erazo’s home on the day of the murder.

                              III.

     At the point the district court would have had to make its
threshold gatekeeping determination for purposes of FRE 702,
the government had yet to disclose the “written summary” of
its expert’s testimony as required by Rule 16(a)(1)(G). The
record does not reveal exactly why. Defense counsel had
alerted the government to its obligation under Rule 16(a)(1)(G)
                                6
two years before trial, and Magnuson was a federal employee
who had previously testified as an expert. To the extent the
trial Assistant U.S. Attorney advised the district court that he
had only obtained the document explaining cell-site analysis
methodology shortly before Magnuson testified on the eighth
day of the jury trial, that did not absolve the government of its
obligations under Rule 16. The government’s “dribbling out”
of information about the nature and scope of its expert’s
testimony never quite described the level of detail on which
Magnuson would testify at trial, much less the methodology he
used, potentially leaving defense counsel unclear about the
nature and scope of his expert testimony.

      The consequence pertinent here is that the government’s
conduct interfered with the district court’s ability to fulfill its
gatekeeping role under Daubert and FRE 702. It hampered the
district court in assessing with any measure of certainty
whether the expert’s testimony would be reliable much less, as
defense counsel feared, would stray at trial beyond the contents
of his “report.” Neither Magnuson’s “report” nor the
government’s representations described the methodology that
he would use to connect appellants’ cell phones to the cell
tower locations. The district court attempted to fill this gap by
relying on descriptions of cell-site methodology in other cases.
This assumed Magnuson’s methodology would be the same in
appellants’ case and limited the court’s ability to pose inquiries
of its own. In opposing the Motion to Exclude, the government
implicitly invited this flawed approach by emphasizing that
cell-site analysts had been accepted as experts by other district
court judges, by arguing that the case appellants relied on where
the district court rejected cell-site expert testimony was
different, and by asserting that peer review was unnecessary
because “cell phone technology is neither novel nor particularly
complex.” Gov’t Opp’n at 6. Although a witness’s testimony
as an expert on a general subject matter in another case may
                                7
inform the Daubert analysis, that circumstance is not sufficient.
The district court’s “gatekeeping inquiry must be tied to the
facts of a particular case.” Kumho Tire, 526 U.S. at 150
(internal quotations omitted). Indeed, “judicial acceptance is
not relevant; what matters is general acceptance in the relevant
expert (scientific or otherwise) community.” United States v.
Hill, 818 F.3d 289, 297 (7th Cir. 2016).

     The district court judge who denied the Motion to Exclude
found Magnuson’s expert opinion reliable based principally on
cell-site analyses accepted by two other district court judges.
Machado-Erazo, 950 F. Supp. 2d at 55-58 (citing United States
v. Jones, 918 F. Supp. 2d 1 (D.D.C. 2013); United States v.
Davis, No. 11-60285-CR, 2013 WL 2156659 (S.D. Fla. May
17, 2013)). In Jones, the district court allowed an FBI agent to
testify as an expert because his cell-site analysis was based on
a reliable methodology, which the government had “clearly
explain[ed],” and the agent did “not purport to portray the
‘coverage area’ of any particular cell tower or antenna.” 918
F. Supp. 2d at 45. In Davis, the district court found, after
holding a Daubert hearing, that Magnuson was “qualified to
opine on call detail records” and “the areas most likely to fall
within the sector serviced by a particular cell tower,” by reason
of his “knowledge, skill, experience, training, and education.”
2013 WL 2156659, at *4.

     If Daubert is to have meaning, then district court had to
satisfy itself that the witness in appellants’ case was an expert
on a particular subject based on the witness’s actual
methodology and the scope of the opinions the witness would
offer at trial. The expert’s testimony in Jones was limited in
scope, and the district court could not assume Magnuson’s
testimony would be the same in appellants’ case as in Davis.
The government’s Rule 16 disclosures and vague
representations were unhelpful in this respect; they did “not . . .
                                8
clearly indicat[e] the level of precision — or imprecision —
with which [cell-site] evidence pinpoints a person’s location at
a given time.” Hill, 818 F.3d at 299. Further, while defense
counsel had alerted the district court to potential flaws in
Magnuson’s methodology, the district court found none,
relying not on the government’s explanation of the
methodology he would use in appellants’ case, but on the
description of his methodology in Davis. See Machado-Erazo,
950 F. Supp. 2d at 55-56. Consulting other judges’ analyses
may be informative or persuasive, but not dispositive. Absent
an independent evaluation of the expert’s methodology and the
nature of the expert’s proposed testimony, real life tragedies
can occur. See, e.g., Pamela Colloff, He Has Spent Three
Decades in Prison. Now Experts Dispute the Evidence., N.Y.
TIMES, July 24, 2018; see also Leora Smith, How an Unproven
Forensic Science Became a Courtroom Staple, PROPUBLICA,
May 31, 2018.

     For much the same reason, Daubert’s monitoring
obligation was frustrated. The district court judge who
presided at appellants’ trial relied on the pretrial Daubert
ruling, which in turn relied on rulings in other cases, including
one that involved a narrower use of a cell-site expert than
occurred at appellants’ trial and another that did not reveal the
scope of Magnuson’s expert testimony. Those rulings could
not eliminate the need to independently monitor the expert’s
testimony at appellants’ trial. Notwithstanding defense
counsel’s alert that Magnuson’s expert testimony could stray
beyond the government’s Rule 16 pretrial disclosure of his
“report,” cf. United States v. Moore, 651 F.3d 30, 60 (D.C. Cir.
2011), Magnuson was allowed to opine that a cell phone “had
to be within a half mile” of a particular tower. Trial Tr. 51 (July
8, 2013). Yet the maps in Magnuson’s “report” contained no
measuring scale and the document produced on the eighth day
of trial stated only that the general range of a cell tower is
                                9
“approximately ONE or TWO miles (greater or less distances
are also common).” Magnuson claimed the basis for his
opinion was “the very nature of the cellular network, the fact
that it’s divided up into cells of [radio frequency] energy.”
Trial Tr. 51 (July 8, 2013). How Magnuson derived “within a
half mile” from those vague statements was explained neither
for the jury nor earlier for the district court. Absent a
foundation, Magnuson’s half-mile opinion was inadmissible
under FRE 702.        Even if the district court had remedial
discretion to deny the defense request that Magnuson be treated
as a lay witness due to the government’s non-compliance with
Rule 16, it was error to allow the jury to consider unsupported
expert testimony.

     In appellants’ case, however, the Rule 16 and Daubert
failings do not entitle them to relief because they show no
prejudice: The government’s evidence of their guilt was strong,
including wiretap and co-conspirator testimony linking them to
the murder, Op. 20-21, and the government’s late Rule 16
disclosures were cumulative of information in its opposition to
the Motion to Exclude. Consequently, “it was highly
improbable that any changes in the facts could have materially
changed the conclusion” of the jury at trial. United States v.
Bresil, 767 F.3d 124, 127 (1st Cir. 2014); see United States v.
Martinez, 657 F.3d 811, 817 (9th Cir. 2011). Still, what
happened here with regard to the admission of Magnuson’s
expert opinion is concerning. Although “the prosecution is
entitled to prove its case by evidence of its own choice,” Old
Chief v. United States, 519 U.S. 172, 186 (1997), one-sided
enforcement of the evidentiary and procedural rules would be
troubling, especially in criminal cases where liberty is at stake.
