United States v. Noe Machado-Erazo , 901 F.3d 326 ( 2018 )


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  •  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.