United States v. Wayne Hill , 818 F.3d 289 ( 2016 )


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  •                               In the
    United States Court of Appeals
    For the Seventh Circuit
    ____________________
    No. 14-2019
    UNITED STATES OF AMERICA,
    Plaintiff-Appellee,
    v.
    WAYNE HILL,
    Defendant-Appellant.
    ____________________
    Appeal from the United States District Court for the
    Northern District of Illinois, Eastern Division.
    No. 11 CR 850-1 — Sharon Johnson Coleman, Judge.
    ____________________
    ARGUED SEPTEMBER 25, 2015 — DECIDED MARCH 21, 2016
    ____________________
    Before WOOD, Chief Judge, and BAUER and EASTERBROOK,
    Circuit Judges.
    WOOD, Chief Judge. They say the house always wins.
    Wayne Hill found out the hard way that if you have robbed
    a bank, that adage applies even if your trip to the casino was
    just to get change. Hill was caught attempting to launder a
    large amount of dye-stained currency, still in bank bands, by
    stuffing the bills into a slot machine at the Horseshoe Casino
    in Hammond, Indiana. He was ultimately convicted of bank
    2                                                   No. 14-2019
    robbery, money laundering, and transportation of stolen
    funds.
    Hill filed pretrial motions to suppress his arrest, the con-
    tents of his bags, and his statements at the time he was
    caught. He also filed a motion in limine seeking to exclude
    expert testimony under Federal Rule of Evidence 702 about
    historical analysis of cellular telephone sites. Hill appeals the
    district court’s denials of all four motions. Because the dis-
    trict court properly resolved each one, we affirm its judg-
    ment.
    I
    On November 19, 2011, Hill walked into the Illiana Fi-
    nancial Credit Union in Naperville, Illinois, pointed a pistol
    at the teller, and ordered her to give him money. While Hill
    threatened repeatedly to shoot her, another teller handed
    over roughly $134,000 in cash. Hill fled the scene with a bag
    full of stacks of wrapped bills.
    At that moment, Hill might have thought he was home
    free. But there was something he did not know: one of the
    tellers had managed to toss a dye pack into the bag along
    with the cash. As Hill fled from the bank, it exploded, stain-
    ing most of his haul a telltale red. Three days later, Hill
    sought to remedy that problem. He drove to the Potawatomi
    Hotel and Casino in Milwaukee, Wisconsin, where he sat
    down in front of a slot machine and fed dye-stained bills into
    it without playing the game. Instead, he cashed out, receiv-
    ing vouchers in the amount of money he had put into the
    machine. After repeating this maneuver on a number of ma-
    chines, he redeemed the vouchers for unstained currency. He
    managed to rid himself of $6,650 in stained bills that night.
    No. 14-2019                                                 3
    On November 26, 2011, Hill tried to repeat his money-
    laundering gambit. He strolled into the Horseshoe Casino in
    Hammond, Indiana, with a backpack and a Santa hat filled
    with thousands of dollars of dye-stained bills. He sat down
    in front of a slot machine and began feeding it cash. But this
    time, a slot attendant noticed what he was doing and
    thought it strange. The slot attendant told Daniel Faulkner, a
    casino security employee, that there was a guest at a slot ma-
    chine with a bag containing a large amount of money. He
    also told Faulkner that the money had red dye on it and that
    the guest was sticking the money into the machine and cash-
    ing it out without playing the slots.
    Faulkner called over the radio, and Monaye Perry, anoth-
    er casino security employee, responded. By the time Perry
    arrived, Hill had told a casino employee that one of his bills
    had gotten stuck in the machine, and a slot attendant had
    opened the machine to recover it. Faulkner told Perry what
    Hill had been doing. Faulkner’s report made Perry suspi-
    cious, because it was very unusual for a guest to be cashing
    out of the machine without playing, not to mention for the
    money to be stained red. Perry questioned Hill briefly. She
    noted that he seemed nervous and hesitant and that he was
    short with his responses. Perry then contacted Eugene
    Kasper, her shift manager. As she did so, Hill abandoned the
    slot machines and moved to the casino’s cash-out area.
    Kasper arrived with company: Hammond Police Lieu-
    tenant Patrick McKechnie. McKechnie was moonlighting as
    a security officer at the casino. Perry relayed Faulkner’s ac-
    count to Kasper and McKechnie and noted that she had re-
    ceived the information from Faulkner himself. McKechnie
    and Kasper followed Hill to the cash-out area and confront-
    4                                                  No. 14-2019
    ed him. As Hill stood in line, McKechnie asked Hill why his
    greenbacks were red and where he had gotten the money.
    Hill did not respond to the first question, but in reply to the
    second he said that he had found the money while changing
    a tire near a lake.
    McKechnie found Hill’s story bizarre and suspicious. He
    knew from his law-enforcement experience that bank em-
    ployees often attempt to hide red dye-packs among stolen
    money during robberies. He could see red dye-stained bills,
    still wrapped in bank bands, in Hill’s hand. Surveillance
    footage shows Kasper examining stacks of cash wrapped in
    bank bands as several casino security personnel stand by. It
    then shows Hill being led away, along with his bag and San-
    ta hat, to an interview room. In the interview room, Hill was
    questioned further and his bag was searched, revealing the
    remainder of the money.
    Hill was indicted for money laundering, bank robbery,
    and transporting stolen money in interstate commerce in vi-
    olation of 
    18 U.S.C. §§ 1956
    (a)(1)(B)(i), 2113(a), (c), and (d),
    and 2314. Before trial, Hill filed motions to suppress his ar-
    rest, the search of his backpack and Santa hat, and his state-
    ments to McKechnie. He also filed a motion in limine seek-
    ing to exclude expert testimony regarding historical cell site
    analysis under Rule 702 of the Federal Rules of Evidence.
    The district court denied all four motions. A jury convicted
    Hill on April 7, 2014, and he was sentenced to 360 months’
    imprisonment. This appeal followed.
    II
    Hill argues that his statements in the cash-out area and
    the evidence seized incident to his arrest should have been
    No. 14-2019                                                     5
    suppressed because (1) Lieutenant McKechnie’s initial con-
    versation with Hill was an arrest for which McKechnie did
    not have probable cause; (2) if that encounter was not an ar-
    rest, McKechnie did not have adequate reasonable suspicion
    to perform an investigatory stop; and (3) McKechnie did not
    have probable cause to remove Hill to the interview room
    where the entirety of Hill’s store of stolen cash was discov-
    ered. He also argues that the district court abused its discre-
    tion in admitting Agent Joseph Raschke’s expert testimony
    regarding historical cell site analysis.
    A
    We look first at Hill’s three motions to suppress. We re-
    view the district court’s rulings under a dual standard: we
    apply the clear error standard to its factual determinations,
    with special deference to the district court’s credibility de-
    terminations, United States v. Villalpando, 
    588 F.3d 1124
    , 1127
    (7th Cir. 2009); we take a de novo approach to its conclusions
    of law. 
    Id.
    1
    Hill contends that his initial encounter with McKechnie
    was an arrest, but we conclude that it was not. A seizure
    qualifies an arrest only if “a reasonable person in the sus-
    pect’s position would have understood the situation to con-
    stitute a restraint on freedom of movement of the degree
    which the law associates with formal arrest.” Abbott v. San-
    gamon Cnty., Ill., 
    705 F.3d 706
    , 719 (7th Cir. 2013). This defini-
    tion is somewhat circular. But it is clear that an arrest re-
    quires at minimum that the subject’s “freedom of movement
    is terminated or restrained by intentionally applied physical
    force or submission to an assertion of authority.” 
    Id.
     (citing
    6                                                    No. 14-2019
    California v. Hodari D., 
    499 U.S. 621
    , 626 (1991)). Importantly,
    contrary to Hill’s arguments, the inquiry is objective and
    “presupposes an innocent person.” 
    Id.
     (citing United States v.
    Drayton, 
    536 U.S. 194
    , 202 (2002)).
    It is hard to offer a crisp definition of what exactly consti-
    tutes an arrest. But courts have made clear that “a brief, on-
    the-spot stop on the street and a frisk for weapons” does not
    qualify. Dunaway v. New York, 
    442 U.S. 200
    , 209 (1979) (citing
    Terry v. Ohio, 
    392 U.S. 1
    , 19–20 (1968)). McKechnie’s interview
    with Hill was not even as intrusive as a stop-and-frisk. He
    made no “assertion of authority” and used no “physical
    force.” Nor did his two questions contain any of the indicia
    of a traditional arrest, no matter the number of casino securi-
    ty personnel who were by then hanging around. At most, the
    interaction represented an investigatory stop. Indeed, the
    government maintains that it was consensual, and therefore
    did not even constitute a seizure under the Fourth Amend-
    ment. But we need not decide whether the interaction was
    consensual: even if it were not, McKechnie’s questioning of
    Hill qualified as a valid investigatory stop.
    An investigatory stop is valid when supported by “a rea-
    sonable, articulable suspicion that criminal activity is afoot.”
    Illinois v. Wardlow, 
    528 U.S. 119
    , 123 (2000). A “reasonable,
    articulable suspicion” is less than probable cause; it requires
    only “a minimal level of objective justification.” 
    Id.
     In decid-
    ing whether the officer’s suspicion was justified, the court
    must consider the “totality of the circumstances” surround-
    ing the stop. United States v. Arvizu, 
    534 U.S. 266
    , 273 (2002).
    The officer may “draw on [his or her] own experience and
    specialized training to make inferences from and deductions
    about the cumulative information available ... that might
    No. 14-2019                                                   7
    well elude an untrained person.”       
    Id.
     (internal quotation
    marks omitted).
    The district court found as a fact that McKechnie had
    learned a great deal before he confronted Hill. Perry had told
    him directly that (1) a slot attendant had seen Hill trying to
    cash out a large amount of red-dyed money through a slot
    machine; (2) the slot attendant had told Faulkner what he
    saw; (3) Faulkner had told Perry; and (4) Perry had ques-
    tioned Hill and found his answers and demeanor suspicious.
    Additionally, McKechnie knew from experience that dye
    packs are used to mark stolen currency. He said that he
    would find it suspicious if someone were using a slot ma-
    chine “as a change machine.” None of these factual findings
    were clearly erroneous. The information McKechnie pos-
    sessed represented far more than “a minimal level of objec-
    tive justification.” See Wardlow, 
    528 U.S. at 123
    . It was suffi-
    cient to arouse reasonable suspicion that Hill had committed
    a crime, and thus to make McKechnie’s interaction with Hill
    in the cash-out area a valid investigatory stop.
    2
    Hill argues that even if his initial interview with
    McKechnie was a valid investigatory stop, he was arrested
    without probable cause when he was escorted to the inter-
    view room. This argument can succeed only if, at that time,
    McKechnie lacked probable cause to believe Hill had com-
    mitted a crime. But the record supports a finding of probable
    cause by then. Hill was therefore validly arrested when he
    was taken to the interview room.
    An arrest is lawful under the Fourth Amendment so long
    as it is made based on probable cause. Rodriguez v. United
    8                                                    No. 14-2019
    States, 
    135 S. Ct. 1609
    , 1621 (2015). Probable cause “means
    facts and circumstances within the officer’s knowledge that
    are sufficient to warrant a prudent person, or one of reason-
    able caution, in believing, in the circumstances shown, that
    the suspect has committed, is committing, or is about to
    commit an offense.” Michigan v. DeFillippo, 
    443 U.S. 31
    , 37
    (1979). Whether probable cause exists is a “commonsense,
    practical question” made considering the totality of the cir-
    cumstances. Illinois v. Gates, 
    462 U.S. 213
    , 230–31 (1983).
    When a court reviews probable cause determinations, the
    evidence must be weighed “as understood by those versed
    in the field of law enforcement.” 
    Id. at 232
     (quoting United
    States v. Cortez, 
    449 U.S. 411
    , 418 (1981)).
    Once he approached Hill in the cash-out line, McKechnie
    could see that Hill was holding a stack of currency stained
    with red dye and wrapped in bank bands. Based on Perry’s
    report, his own observations, and his prior experience,
    McKechnie surmised that the money was from a bank rob-
    bery and that Hill was trying to launder it. McKechnie asked
    Hill why the money was dyed red and where he had ob-
    tained it. Hill initially refused to answer either question, but
    then offered the unlikely story that he found it while chang-
    ing a tire by a lake. Hearing this, McKechnie was justifiably
    suspicious. A reasonably prudent person in McKechnie’s po-
    sition would think that Hill had committed or was commit-
    ting a crime. See, e.g., United States v. Curry, 
    538 F.3d 718
    , 730
    (7th Cir. 2008) (search warrant based largely on observation
    of suspect handling red-dyed currency “clearly supported a
    determination of probable cause”). McKechnie therefore had
    probable cause to arrest Hill.
    No. 14-2019                                                  9
    3
    Finally, the search that revealed Hill’s remaining currency
    was unobjectionable. A search incident to arrest is valid if it
    does not extend beyond “the arrestee’s person and the area
    within his immediate control.” Arizona v. Gant, 
    556 U.S. 332
    ,
    339 (2009) (internal quotation marks omitted). The zone of
    “immediate control” includes “the area from within which
    [the suspect] might gain possession of a weapon or de-
    structible evidence.” 
    Id.
     When he was detained, Hill was
    holding the bag containing his hoard of dye-stained cash
    and was plainly exercising immediate control over it.
    McKechnie’s search was therefore a permissible search inci-
    dent to arrest, and the district court was correct to deny
    Hill’s motions to suppress.
    B
    Hill’s other argument focuses on expert testimony from
    Agent Raschke about historical cell-site analysis. This testi-
    mony, he contends, violated Federal Rule of Evidence 702
    because the district court improperly applied the rule and
    the Supreme Court’s framework in the line of cases begin-
    ning with Daubert v. Merrell Dow Pharm., Inc., 
    509 U.S. 579
    ,
    589 (1993). We review the analytical approach the district
    court took de novo and its application of that framework to
    the facts before it for abuse of discretion. Lees v. Carthage
    Coll., 
    714 F.3d 516
    , 520 (7th Cir. 2013).
    Historical cell-site analysis uses cell phone records and
    cell tower locations to determine, within some range of error,
    a cell phone’s location at a particular time. A cell phone is
    essentially a two-way radio that uses a cellular network to
    10                                                    No. 14-2019
    communicate. Aaron Blank, The Limitations and Admissibility
    of Using Historical Cellular Site Data to Track the Location of A
    Cellular Phone, 18 RICH. J.L. & TECH. 3, 5 (2011). Each cell
    tower covers a certain geographic area. That geographic area
    depends upon “the number of antennas operating on the cell
    site, the height of the antennas, topography of the surround-
    ing land, and obstructions (both natural and manmade).” 
    Id.
    In urban areas, cell towers may be located every one-half to
    one mile, while cell sites in rural areas may be three to five
    miles apart. 
    Id.
     When a cell phone user makes a call, the
    phone generally “connect[s] to the cell site with the strongest
    signal,” although “adjoining cell [towers] provide some
    overlap in coverage.” 
    Id.
     While the proximity of the user is a
    significant factor in determining the cell tower with which
    the cell phone connects, it is not the only one. 
    Id.
     Other fac-
    tors include the towers’ technical aspects, including geogra-
    phy and topography, the angle, number, and directions of
    the antennas on the sites, the technical characteristics of the
    relevant phone, and “environmental and geographical fac-
    tors.” 
    Id. at 7
    .
    The parties here do not dispute that testimony about his-
    torical cell-site analysis is expert testimony. That proposition
    is not, however, universally applied, and perhaps not even
    universally accepted. Some circuits have treated some kinds
    of historical cell-site analysis as lay testimony. See, e.g., Unit-
    ed States v. Graham, 
    796 F.3d 332
    , 364 (4th Cir. 2015) (finding
    no abuse of discretion in admitting Sprint/Nextel employee’s
    lay testimony that cell phones connect to the tower emitting
    the strongest signal and cell towers in urban areas have a
    two-mile maximum range, and law enforcement officer’s lay
    testimony and maps regarding the defendant’s location
    based on cell phone records and cell sites); United States v.
    No. 14-2019                                                  11
    Henderson, 564 F. App’x 352, 364 (10th Cir. 2014) (nonprece-
    dential) (law enforcement agent’s plotting of the defendant’s
    locations through historical cell-site analysis was proper lay
    testimony so long as the agent did not testify about how cell
    towers operate), reh’g en banc granted, 624 F. App’x 75 (4th
    Cir. 2015).
    Agent Raschke’s testimony in this case included state-
    ments about how cell phone towers operate. In our view, this
    fits easily into the category of expert testimony, such that
    Rule 702 governs its admission. See Graham, 796 F.3d at 364
    (holding historical cell-site analysis testimony about how cell
    phones and towers connect “clearly ‘based on scientific,
    technical, or specialized knowledge within the scope of Rule
    702.’” (quoting FED. R. EVID. 701(c))); United States v. Yeley-
    Davis, 
    632 F.3d 673
    , 684 (10th Cir. 2011) (“[T]estimony con-
    cerning how cell phone towers operate constituted expert
    testimony because it involved specialized knowledge not
    readily accessible to any ordinary person.”).
    When evaluating whether an expert’s testimony should
    be admitted, a court must consider whether the expert’s tes-
    timony is “supported by appropriate validation” and “will
    assist the trier of fact to understand or determine a fact in
    issue.” Daubert, 
    509 U.S. at
    590–92; Kumho Tire Co. v. Carmi-
    chael, 
    526 U.S. 137
    , 147 (1999) (extending the Daubert’s “gate-
    keeping function” to all expert evidence). Rule 702’s purpose
    is to “establish[] a standard of evidentiary reliability.” Kumho
    Tire, 
    526 U.S. at 149
     (quoting Daubert, 
    509 U.S. at 590
    ). The
    Supreme Court emphasized the importance of carefully vet-
    ting expert testimony, noting that it “can be both powerful
    and quite misleading because of the difficulty in evaluating
    it.” Daubert, 
    509 U.S. at 595
     (quoting Jack B. Weinstein, Rule
    12                                                   No. 14-2019
    702 of the Federal Rules of Evidence Is Sound; It Should Not Be
    Amended, 
    138 F.R.D. 631
    , 631–32 (1991)).
    Rule 702 sets out four criteria for the admission of expert
    testimony:
    (a) the expert’s scientific, technical, or other special-
    ized 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. In applying those criteria, courts must also
    bear in mind the fact that “the gatekeeping inquiry must be
    tied to the facts of a particular case.” Kumho Tire, 
    526 U.S. at 150
     (internal quotation marks omitted). The trial judge has
    “broad latitude” to determine how to evaluate expert testi-
    mony and whether to hold an evidentiary hearing in any
    particular case. 
    Id. at 153
    .
    District courts that have been called upon to decide
    whether to admit historical cell-site analysis have almost
    universally done so. See United States v. Jones, 
    918 F. Supp. 2d 1
    , 5 (D.D.C. 2013) (collecting cases). Ironically, one of the few
    exceptions involved Agent Raschke himself. See United States
    v. Evans, 
    892 F. Supp. 2d 949
    , 956 (N.D. Ill. 2012) (admitting
    traditional historical cell-site analysis, but rejecting Raschke’s
    novel and “wholly untested” theory of “granulization”). The
    government argues that the numerous district court deci-
    sions to admit historical cell-site analysis constitute “general
    No. 14-2019                                                   13
    acceptance” of the technique. But judicial acceptance is not
    relevant; what matters is general acceptance in the relevant
    expert (scientific or otherwise) community. See Daubert, 
    509 U.S. at 594
    ; Gen. Elec. Co. v. Joiner, 
    522 U.S. 136
    , 148 (1997)
    (Breyer, J., concurring) (“[J]udges are not scientists and do
    not have the scientific training that can facilitate the making
    of such decisions.”).
    No federal court of appeals has yet said authoritatively
    that historical cell-site analysis is admissible to prove the lo-
    cation of a cell phone user. The Sixth Circuit gave the tech-
    nique an unfavorable appraisal recently in United States v.
    Reynolds, 626 F. App’x 610, 616–17 (6th Cir. 2015) (nonprece-
    dential). Because the government there used historical cell-
    site analysis to prove that certain people were not in a certain
    area at a particular time, the court did not need to rule on the
    technique’s reliability for proving where a person was at a
    given time. The court noted, however, that claims of success-
    ful use by law enforcement personnel were “precisely the
    sort of ‘ipse dixit of the expert’ testimony that should raise a
    gatekeeper’s suspicion,” were it “not subject to independent
    peer review,” and “fail[ed] to establish an error rate with
    which to assess reliability because there was no information
    on how many times the technique was employed unsuccess-
    fully.” Id. at 616 (quoting Kumho Tire, 
    526 U.S. at 157
    ). The
    Fifth Circuit, in contrast, has affirmed the admission of his-
    torical cell-site analysis under Rule 702 to prove an individ-
    ual’s location. See United States v. Schaffer, 439 F. App’x 344,
    347 (5th Cir. 2011) (nonprecedential). But the Sixth Circuit
    singled out Schaffer for criticism in Reynolds. 626 F. App’x at
    616–17. And even the Fifth Circuit only remarked that
    “[t]estimony established that the field is neither untested nor
    14                                                No. 14-2019
    unestablished.” 439 F. App’x at 347. This is hardly a ringing
    endorsement.
    The contested cell-site analysis in Hill’s case covers two
    days. The first is November 14, 2011. Agent Raschke testified
    that Hill’s cell phone records and the locations of relevant
    cell towers indicated that on that day, Hill’s T-Mobile cell
    phone used a tower that was roughly a mile and half from
    the Credit Union that was later robbed. Agent Raschke also
    used historical cell-site analysis to trace the whereabouts of
    Hill’s phone on November 19, 2011, the day of the robbery.
    Most significantly, Agent Raschke testified that at 11:54 am—
    16 minutes after the robber fled the Credit Union—Hill’s
    Nextel phone engaged a tower in Naperville, Illinois, that
    was located approximately 11 miles east of the Credit Union
    and 35 miles south of Hill’s residence. Agent Raschke then
    traced connections between Hill’s cell phone and towers
    moving north along the interstate. The clear implication of
    the testimony was that Hill’s cell phone was in the general
    area of the Credit Union shortly after the robbery, and then
    moved rapidly northward along the highway immediately
    afterward. It wound up near his residence at 12:28 pm before
    moving north again at 1:08 pm and ending at his work ad-
    dress at 1:33 pm.
    The government used Agent Raschke’s historical cell-site
    analysis against Hill for two purposes at closing. The first
    was to argue that Hill’s alibi statement to Agent Hoogland—
    that he was at work at 12:30 pm on November 19, 2011, and
    therefore could not have been at the Credit Union at 11:38
    am—was a lie. As this involved proving where Hill was not,
    rather than where he was, this use is uncontroversial. See,
    e.g., Reynolds, 626 F. App’x at 617. But, more problematically,
    No. 14-2019                                                     15
    the government used Agent Raschke’s testimony to argue
    that Hill was in the general vicinity of the Credit Union 16
    minutes after it was robbed on that day, and that he then
    drove rapidly north back to his house, before continuing on
    to work 40 minutes later.
    In his trial testimony, Agent Raschke emphasized that
    Hill’s cell phone’s use of a cell site did not mean that Hill was
    right at that tower or at any particular spot near that tower.
    This disclaimer saves his testimony. Historical cell-site anal-
    ysis can show with sufficient reliability that a phone was in a
    general area, especially in a well-populated one. It shows the
    cell sites with which the person’s cell phone connected, and
    the science is well understood. Evans, 892 F. Supp. 2d at 956
    (noting that methods of “historical cell site analysis can be
    and have been tested by scientists”). The technique requires
    specialized training, which Agent Raschke has and has em-
    ployed successfully on hundreds of occasions. A mathemati-
    cal error rate has not been calculated, but the technique has
    been subjected to publication and peer criticism, if not peer
    review. See, e.g., Matthew Tart et al., Historical Cell Site Analy-
    sis – Overview of Principles and Survey Methodologies, 8 DIGITAL
    INVESTIGATION 185–86 (2012); Blank, 18 RICH. J.L. & TECH. at
    3–5; Herbert B. Dixon Jr., Scientific Fact or Junk Science? Track-
    ing A Cell Phone Without GPS, 53 JUDGES’ J. 37 (2014). The ad-
    vantages, drawbacks, confounds, and limitations of histori-
    cal cell-site analysis are well known by experts in the law en-
    forcement and academic communities. Agent Raschke de-
    scribed many of them at trial.
    Nonetheless, we have some concerns about Agent
    Raschke’s testimony. On cross-examination, he admitted that
    he did not know any of the particular characteristics of the
    16                                                 No. 14-2019
    cell tower with which Hill’s phone connected at 11:54 am,
    including its power or the direction its antennae were facing.
    He did not perform any tests of that cell tower’s area of sig-
    nal coverage. Based on his experience, he disputed defense
    counsel’s suggestion that a cell phone could connect from 20
    or 10 miles away from a particular cell site, but he admitted
    that it could travel “over 5 miles.” On re-direct he stated that
    his experience was that the range of Chicago area towers
    was “very limited,” and that he had never, in hundreds of
    investigations in Chicago, seen a cell phone “jump” to con-
    nect with a cell tower 20 miles away. Based on this testimony,
    the jury could reasonably and reliably infer that at 11:54 am
    on November 19, 2011, Hill was within a five-mile radius of
    the cell tower located 11 miles east of the Credit Union. The
    testimony is relevant and probative, and therefore somewhat
    helpful to the trier of fact—even if not that helpful.
    Our concern is that the jury may overestimate the quality
    of the information provided by this analysis. We therefore
    caution the government not to present historical cell-site ev-
    idence without clearly indicating the level of precision—or
    imprecision—with which that particular evidence pinpoints
    a person’s location at a given time. The admission of histori-
    cal cell-site evidence that overpromises on the technique’s
    precision—or fails to account adequately for its potential
    flaws—may well be an abuse of discretion. In this case, how-
    ever, Agent Raschke’s testimony on both direct and cross-
    examination made the jury aware not only of the technique’s
    potential pitfalls, but also of the relative imprecision of the
    information he gleaned from employing it in this case. The
    science and methods upon which the technique is based are
    understood and well documented. Admitting Agent
    Raschke’s testimony was therefore not an abuse of the dis-
    No. 14-2019                                                17
    trict court’s considerable discretion under either Rule 702 or
    Rule 403.
    III
    Because the district court did not err in denying any of
    Hill’s four motions, we AFFIRM its judgment.