Court Opinion

ID: 7798294
Source: CourtListenerOpinion
Date Created: 2022-08-05 16:00:41.569768+00
Date Added: 2024-06-11T16:28:46.669680
License: Public Domain

United States Court of Appeals
         FOR THE DISTRICT OF COLUMBIA CIRCUIT

Argued April 23, 2021                 Decided August 5, 2022

                        No. 18-3045

                UNITED STATES OF AMERICA,
                        APPELLEE

                              v.

                   CHARLES MORGAN, JR.,
                       APPELLANT

        Appeal from the United States District Court
                for the District of Columbia
                   (No. 1:16-cr-00196-1)

    Lisa Wright, Assistant Federal Public Defender, argued the
cause for appellant. With her on the briefs was A. J. Kramer,
Federal Public Defender. Tony Axam Jr. and Michelle M.
Peterson, Assistant Federal Public Defenders, entered
appearances.

    Daniel J. Lenerz, Assistant U.S. Attorney, argued the
cause for appellee. With him on the brief were Elizabeth
Trosman and Elizabeth H. Danello, Assistant U.S. Attorneys.

    Before: SRINIVASAN, Chief Judge, KATSAS, Circuit Judge,
and SENTELLE, Senior Circuit Judge.
                                2
    Opinion for the Court filed by Chief Judge SRINIVASAN.

     SRINIVASAN, Chief Judge: Appellant Charles Morgan, Jr.
was indicted for transportation of a minor with intent to engage
in criminal sexual activity, attempted production of child
pornography, and commission of a felony involving a minor by
a person required to register as a sex offender. After a
bifurcated jury and bench trial, Morgan was convicted on all
counts.

     On appeal, Morgan brings three challenges to his
convictions. First, he contends that the district court abused its
discretion by admitting the government’s expert testimony
concerning the approximate locations of Morgan’s and the
transported minor’s cell phones on the night of their meeting.
Second, Morgan argues that the government should have been
required to prove not just that he transported a minor to engage
in sexual activity, but that he knew she was underage. Third,
Morgan challenges the constitutionality of the Act that required
him to register as a sex offender. Because we are unpersuaded
by Morgan’s arguments, we affirm.

                                I.

                               A.

     In November 2016, a grand jury charged Charles Morgan,
Jr. with transportation of a minor with intent that the minor
engage in sexual activity for which any person could be
criminally charged, in violation of 18 U.S.C. § 2423(a);
attempted production of child pornography, in violation of 18
U.S.C. § 2251(a), (e); and two counts of commission of a
felony involving a minor by a person required to register as a
sex offender, in violation of 18 U.S.C. § 2260A.
                                 3
     Pursuant to the parties’ stipulation, the district court held a
bifurcated trial. The court first held a jury trial on the
transportation and child pornography charges.                   The
government put forth the following facts in the jury trial. The
defense did not put on a case.

     In May 2016, J.T. was 15 years old and lived with her
mother in an apartment in Southeast Washington, D.C. On
May 22, a Sunday, J.T. was at her grandmother’s house in
Southwest D.C., where she planned to stay overnight. But after
getting into an argument with her cousin that evening and
sensing her grandmother’s resulting frustration, J.T. decided to
sneak out of her grandmother’s house and return home.

     J.T. took the bus part of the way home and walked the
remainder of the way. When J.T. arrived at her apartment
building in Southeast D.C., she could not get into her
apartment—she did not have keys, the lights in the apartment
were off, and she was unable to reach her sister. J.T. decided
to meet a friend with whom she had been texting and then to
spend the night at the home of her friend’s sister. After learning
that the bus would not arrive at the nearest stop for another 20
to 25 minutes, J.T. decided to walk along the bus route toward
Pennsylvania Avenue, where she was to meet her friend. She
eventually reached Randle Circle—still in Southeast D.C.—
where she stopped to wait for the bus because she was tired and
her phone battery had died.

     While J.T. waited for the bus at Randle Circle, a car pulled
over and idled for a few minutes. The driver—Charles
Morgan, Jr., then 55 years old—rolled down his window and
asked J.T. if she wanted a ride. J.T. did not respond and turned
away. Morgan then told her that he “wouldn’t do things like
that,” showed her “a government I.D.,” and gave her a business
card. Apr. 27, 2018 Trial Tr. 129:11–30:22, App. 982–83. J.T.
                                4
decided to get in Morgan’s car because “he seemed old” and
“like he wouldn’t do nothing like that.” Id. at 131:18–19, App.
984. Morgan then asked for her name, her age, and where she
lived. J.T. told him that she was 14 but did not answer the other
questions.

     Instead of driving her home, Morgan drove to another part
of Southeast D.C. and stopped the car near the Fort Davis
Recreation Center. J.T. recognized the location because her
mother had worked there in the summer. Morgan then fondled
J.T. in the car and forced her to perform fellatio on him.

     After J.T. sat back up, Morgan began driving again. J.T.
saw them pass a “Welcome to D.C.” sign on the driver’s side
of the car. Morgan drove into Maryland, parked at a house, and
led J.T. into the basement apartment. Morgan told J.T. to get
on the bed, where he proceeded to sodomize her. After he
stopped sodomizing J.T., Morgan eventually led J.T. back to
the car.

     Morgan drove J.T. to her requested location in Southeast
D.C, around the corner from her mother’s apartment, and gave
her his number. J.T. went inside the apartment and told her
mother what had happened. They reported the incident to the
police shortly thereafter.

     Later that week, a police detective obtained J.T.’s consent
to assume J.T.’s identity and start communicating with
Morgan. After the detective (pretending to be J.T.) and
Morgan exchanged several text messages, Morgan asked J.T.
to send him a picture of her genitalia. In response, the detective
set up a recorded call between Morgan and J.T. On the call,
Morgan reiterated his request for the picture. After Morgan
briefly hung up, they got back on the phone and J.T. said she
was just 14 years old. Morgan reacted with apparent surprise
                               5
and hung up again. Morgan tried calling J.T. several times later
that night but did not reach her. The detective and Morgan
exchanged sporadic text messages for the next several days
until Morgan stopped communicating.

                              B.

                               1.

     To demonstrate a violation of 18 U.S.C. § 2423(a) (the
transportation charge), the government needed to prove that
Morgan had transported J.T. from D.C. to Maryland on the
night she rode in his car, May 22. To that end, the government
sought to call FBI Special Agent Kevin Horan as an expert
witness to opine about the locations of J.T.’s and Morgan’s cell
phones during that night. Horan’s testimony would be based
on the results of a “drive test,” and it was meant to support
J.T.’s account that Morgan had transported her from D.C. to
Maryland.

     A drive test is a method of identifying the coverage range
of a cell tower. Drive tests are used primarily “by wireless
telephone companies and radio frequency engineers to
determine . . . the health of the telephone company’s wireless
network.” Larry Daniel, Cell Phone Location Evidence for
Legal Professionals: Understanding Cell Phone Location
Evidence from the Warrant to the Courtroom 69 (2017). Law
enforcement personnel also conduct drive tests, typically to
determine the approximate coverage area of a particular tower
to which a cell phone of interest connected during a relevant
time period. See Aug. 22, 2017 Daubert Hearing Tr. 11:8–
17:20, App. 467–73; see also Daniel, supra, at 69–71; United
States v. Nelson, 533 F. Supp. 3d 779, 786 (N.D. Cal. 2021).
By determining a tower’s coverage area, law enforcement can
                                6
narrow down the cell phone’s location when it connected to
that tower.

     After the government indicated its intention to call Horan
as a witness at trial to give testimony about drive tests he had
conducted in connection with this case, Morgan moved to
exclude the testimony. The district court then held a multi-day
Daubert hearing on the admissibility of Horan’s testimony.
See Daubert v. Merrell Dow Pharms., Inc., 509 U.S. 579
(1993). Horan stated at the hearing that he has been a member
of the FBI’s cellular analysis survey team (CAST) since its
inception in 2007. He annually conducts an average of twenty
to thirty drive tests. Before Morgan’s trial, Horan had testified
as an expert seventy-six times, and in the last several years,
almost all of his cases involved drive tests. The district court
accepted Horan as an expert in “historical cell site analysis,
which includes the drive test.” Aug. 22, 2017 Daubert Hearing
Tr. 10:22-23, App. 466.

     Horan told the court that he prepares for a drive test by
analyzing call-detail records to understand which cell phone
towers a cell phone communicated with during the relevant
time period. He then creates a “target area” containing both the
“target tower” and “the other towers that are surrounding it.”
Id. at 23:19–24:3, App. 479–80. Using that area, Horan
generates a planned route that he will drive with the testing
equipment. He conducts the drive test by driving along the
planned route with a device—the Gladiator Autonomous
Receiver (GAR)—manufactured by a company named
Gladiator. The GAR collects radio frequencies and GPS data
and stores them in a computer system. Horan typically drives
until he becomes satisfied that he has “gone through all the
different parts of [the] target area, . . . gone by the [relevant]
addresses, [and] . . . gone around the tower enough times on
certain streets.” Id. at 28:14–16, App. 484. The drive tests
                                7
typically “take[] more than one day” to complete. Id. at 27:25,
App. 483.

    After completing the driving portion of a drive test, Horan
processes the collected data through Gladiator’s proprietary
software program, Enterprise Sensor Processing and Analytics
(ESPA).     The software generates maps depicting the
approximate coverage area of the towers of interest. Another
agent then independently reviews the collected data and the
ESPA analysis to check whether there were any errors. When
asked how the software processes the data, Horan explained he
had not been granted permission to access and examine the
underlying software code and thus was unsure precisely how it
functioned.

     For this case, Horan had conducted a two-day drive test on
November 28 and December 1, 2016. He intended to evaluate
the coverage area of the cell phone towers used by J.T.’s T-
Mobile phone and Morgan’s Sprint phone from approximately
11:00 p.m. to 1:00 a.m. on May 22–23. Horan examined their
phone records to identify the towers to which their phones had
connected during that two-hour window, developed his route,
and conducted the drive test to determine where the phones
could have been located when they connected to particular
towers. After completing the test, Horan used the ESPA
software to generate a number of maps showing the results of
his testing.

     At the Daubert hearing, Horan presented those maps and
other slides to the district court. The slides showed his intended
driving route, his actual driving route, and his findings with
respect to the coverage of a particular cell tower, which he used
as an example to demonstrate the type of results his testing
produced.
                                8
     Morgan called his own expert witness to testify about drive
testing. The defense witness agreed with Horan that, in theory,
a drive test “can give you a better defined area than” other
forms of cell-site location analysis, “depending on the process
and how it’s done.” Oct. 11, 2017 Daubert Hearing Tr. 13:22–
14:5, App. 653–54. The defense witness also opined that
Horan’s drive test did not cover a large enough area to
determine with precision where a phone could no longer
connect to a particular tower. The expert conceded, however,
that towers in cities may have smaller coverage areas. That is
because, in dense urban areas, providers use “down tilt”—i.e.,
they direct a tower’s signal “into the ground so that it ends at
[a] point”—to prevent interference from other towers. Id. at
66:7–19, App. 706.

     The district court denied Morgan’s motion to exclude
Horan’s testimony. United States v. Morgan, 292 F. Supp. 3d
475 (D.D.C. 2018). With regard to Morgan’s reliability
challenge under Federal Rule of Evidence 702, the court held
that the drive-test methodology at issue exhibited sufficient
indicia of reliability to allow Horan to testify before the jury.
Id. at 484–85. The court also held that Horan’s testimony
would not be unduly misleading in violation of Federal Rule of
Evidence 403. The court determined that his “testimony will
not mislead the jury so long as he testifies only to defendant’s
and the alleged victim’s possible location within a general area
of coverage, as opposed to an exact location.” Id. at 486.

                                2.

     Horan testified at the jury trial (after J.T.’s testimony). He
explained that he used Gladiator’s software to process the
results of his test and generate maps “that are the actual
footprint of the cell tower[s]” that connected to J.T. and
                               9
Morgan’s phones on the night of May 22. Apr. 30, 2018 Trial
Tr. 160:13–14, App. 1230.

     Using those maps, Horan opined that at around 11:30 p.m.
that night, J.T.’s phone connected to a T-Mobile tower whose
coverage area was entirely within D.C. He also presented a
map showing the approximate location of J.T.’s phone at 11:58
p.m. and Morgan’s phone at 12:09 a.m. The map again showed
coverage areas completely within D.C. Last, Horan showed
maps identifying the general location of Morgan’s phone
between approximately 12:11 and 1:04 am. The last of those
maps showed a coverage area that included Morgan’s home in
Maryland.

     At the close of the weeklong jury trial, the jury convicted
Morgan on the counts alleging transportation of a minor and
attempted production of child pornography.             The jury
instructions for the transportation charge did not require the
jury to find that Morgan knew J.T.’s age when he transported
her from D.C. to Maryland.

                               3.

     The district court considered the remaining counts at a
stipulated bench trial. Morgan did not dispute that he had been
previously convicted of an offense that required him to register
as a sex offender under the Sex Offender Registration and
Notification Act (SORNA). He contended, however, that
application of the registration requirement to individuals like
him, who had been convicted of sex offenses before SORNA’s
enactment, violated the nondelegation doctrine. The district
court rejected that argument and found Morgan guilty of the
two sex offender registration counts. The court then sentenced
Morgan to 480 months of imprisonment.
                              10
                              II.

    Morgan first contends that the district court erred in
admitting Horan’s expert testimony about his drive tests.
According to Morgan, the testimony should have been
excluded either as unreliable under Federal Rule of Evidence
702 or as misleading under Federal Rules of Evidence 403. We
disagree and sustain the district court’s decision to admit
Horan’s testimony.

                              A.

     We “must afford trial judges great discretion” in admitting
or excluding expert testimony. United States v. Day, 524 F.3d
1361, 1367 (D.C. Cir. 2008). We thus review such decisions
for an abuse of discretion. United States v. McGill, 815 F.3d
846, 903 (D.C. Cir. 2016). And we “grant[] a district court the
same broad latitude when it decides how to determine
reliability as it enjoys in respect to its ultimate reliability
determination.” Kumho Tire Co. v. Carmichael, 526 U.S. 137,
142 (1999) (citing General Electric Co. v. Joiner, 522 U.S.
136, 143 (1997)).

     Federal Rule of Evidence 702 governs the admissibility of
expert testimony. Under the Rule, a “witness who is qualified
as an expert by knowledge, skill, experience, training, or
education may testify . . . 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.
                                11
     In Daubert v. Merrell Dow Pharmaceuticals, Inc., 509
U.S. 579 (1993), the Supreme Court identified various factors
that can inform the reliability analysis under Rule 702. Those
factors include whether the expert’s “theory or technique” (i)
“can be (and has been) tested,” (ii) “has been subjected to peer
review and publication,” (iii) has a high “known or potential
rate of error,” and (iv) enjoys “‘general acceptance’ within a
“relevant scientific community.” Id. at 593–94 (citation
omitted). But the Daubert factors “do not constitute a
definitive checklist or test” applicable in every case. Kumho
Tire Co., 526 U.S. at 150 (citation and quotation marks
omitted).

     The district court in this case did not abuse its discretion
in admitting Horan’s testimony under Rule 702.

     First, Morgan understandably “is not challenging Horan’s
expert qualifications,” Morgan Reply Br. 4, and does not
dispute that Horan possesses the requisite “specialized
knowledge.” Fed. R. Evid. 702(a). Horan performs dozens of
drive tests each year, teaches classes on drive testing, has a
valid certification to use drive-test equipment, and has
repeatedly been certified as an expert on cell phone analysis in
cases involving drive tests. Morgan, 292 F. Supp. 3d at 478.

     Nor does Morgan deny that Horan’s testimony “help[ed]
the trier of fact to . . . determine a fact in issue.” Fed. R. Evid.
702(a). After all, the government needed to show that Moran
drove J.T. from D.C. to Maryland in order to prove that he
transported a minor in interstate commerce in violation of 18
U.S.C. § 2423(a). J.T. gave direct testimony to that effect, and
Horan’s drive-test testimony aimed to show that the
approximate locations of Morgan’s and J.T.’s cell phones
during the evening supported her testimony.
                               12
      Second, the district court reasonably determined that
Horan’s “testimony [was] based on sufficient facts or data.”
Fed. R. Evid. 702(b). On this score, Morgan’s sole objection
is that Horan drove an insufficient distance in carrying out the
drive test. Morgan argues that, in light of the typical coverage
radius of a cell tower, Horan’s drive test did not encompass a
large enough area to properly confirm the coverage range of
the relevant towers.

     The district court understood the issue: the court
recognized that the “distance covered in a drive test can affect
the accuracy of the results it produces,” and noted the view
expressed by Morgan’s witness in the Daubert hearing “that
Agent Horan did not drive far enough to produce an accurate
drive test.” Morgan, 292 F. Supp. 3d at 482–83. The court
also took note of Horan’s explanation that the signal distances
of cell phone towers are more circumscribed “in an urban
environment.” Id. In ultimately allowing Horan to testify, the
court left questions about the distances he drove in carrying out
the drive test for the jury to consider in weighing the force of
his presentation.

     That decision was within the district court’s discretion.
Daubert cautions against being “overly pessimistic about the
capabilities of the jury and of the adversary system generally.”
509 U.S. at 596. And the Daubert Court emphasized that
“[v]igorous cross-examination, presentation of contrary
evidence, and careful instruction on the burden of proof are the
traditional and appropriate means of attacking shaky but
admissible evidence.” Id. The district court justifiably
concluded that concerns about the specific distances Horan
drove in this case should be considered by the jury in assessing
the weight of Horan’s testimony, and not by the court in its
threshold admissibility determination. See id. at 597.
                               13
     Morgan’s contention that Horan did not drive far enough
from the relevant cell phone towers to develop complete
coverage maps is not an indictment of drive-test methodology
generally. Instead, his challenge concerns whether Horan’s
execution of the drive test in this case enabled gathering
sufficient information to sustain a case-specific conclusion:
that Morgan could not have been in Maryland when he
connected to certain towers. And “efforts to discredit [an
expert’s] methodology by pointing to the limits of the research
he undertook” generally “go[] to the weight rather than the
admissibility of his testimony.” Ambrosini v. Labarraque, 101
F.3d 129, 140 (D.C. Cir. 1996); see also, e.g., United States v.
Hodge, 933 F.3d 468, 478 (5th Cir. 2019); Hartley v. Dillard’s,
Inc., 310 F.3d 1054, 1061 (8th Cir. 2002).

     In fact, Morgan acknowledges that there “would have been
nothing wrong with” Horan’s conduct of the drive test if the
results been used to demonstrate only that the cell tower signals
were “consistent” with J.T.’s testimony about Morgan’s
locations during the night. Morgan Br. 43. The problem, in
Morgan’s view, was that “the government wanted more than
just ‘consistency,’”—it instead ostensibly sought to “exclude
Morgan being anywhere . . . in Maryland” at certain times. Id.
Yet if Horan executed the drive test in a sufficiently sound
manner to enable drawing some conclusions about J.T.’s and
Morgan’s cell phone locations at the relevant times, then
questions about the adequacy of the test for a particular
conclusion speak more about the weight of the evidence in
supporting that conclusion than its admissibility at the outset.
As we have explained, the admissibility of expert testimony
turns not on “the accuracy of the conclusion” the expert
proffers—a question generally left to the factfinder—but on
“the soundness of the methodology” she employs. Ambrosini,
101 F.3d at 140.
                               14
     To that end, Morgan could have cross-examined Horan
about the area he drove relative to a cell tower’s typical
coverage radius, or pressed him about the possibility of
undiscovered signal islands that might have placed Morgan in
Maryland during relevant parts of the night. Morgan opted not
to do so. In these circumstances, a threshold admissibility
challenge under Rule 702 does not serve as a substitute for
forgone opportunities to challenge the weight of expert
testimony before the jury.

     Third, the district court acted within its discretion in
determining that Horan’s testimony was “the product of
reliable principles and methods.” Fed. R. Evid. 702(c). The
court acknowledged “that drive testing technology has been
relied upon, tested and reviewed for decades in the multibillion
dollar wireless communications industry.” See Morgan, 292 F.
Supp. 3d at 484 n.7 (citation and quotation marks omitted).
Morgan’s own expert echoed that understanding. Aug. 22,
2017 Daubert Hearing Tr. 31:14–21, App. 487; Oct. 11, 2017
Daubert Hearing Tr. 15:25–16:10, App. 655–56. And Morgan
concedes that “the cell industry considers ESPA a useful tool
for maximizing customer satisfaction.” Morgan Br. 39. While
industry and law enforcement use the results of their drive tests
for different ultimate purposes, the direct objective of a drive
test performed by either user is the same: to map the coverage
of a cell tower. See Daniel, supra, at 69–71. It is perhaps
unsurprising, then, that drive testing has become somewhat
common in law enforcement settings. See, e.g., State v.
Montanez, 197 A.3d 959, 979 (Conn. App. Ct. 2018); Nelson,
533 F. Supp. 3d at 786.

     The district court also analogized drive testing to a similar
technique that enjoys widespread use by law enforcement:
historical cell-site analysis. Courts have generally found
historical cell-site analysis to be reliable and admissible. See
                                 15
United States v. Hill, 818 F.3d 289, 295–99 (7th Cir. 2016); see
also United States v. Pembrook, 876 F.3d 812, 824–25 (6th Cir.
2017), vacated on other grounds, Calhoun v. United States,
139 S. Ct. 137 (Mem.) (2018). At a high level, historical cell-
site analysis entails examining a cell phone’s historical records,
determining the tower to which the phone connected at a
particular time, and using a rough estimate of the coverage
“wedge” of the tower to narrow down the general location of
the cell phone at that time. See, e.g., United States v. Jones,
918 F. Supp. 2d 1, 3, 5 (D.D.C. 2013); Hill, 818 F.3d at 295–
96. Drive testing aims to ascertain the contours of a cell
tower’s coverage area with greater precision by collecting
radiofrequency signals from the tower. Morgan, 292 F. Supp.
3d at 480; Oct. 11, 2017 Daubert Hearing Tr. 13:22–14:1, App.
653–54. But both methods rest on the same, overarching
principle: that coupling information about a tower’s coverage
radius with the time at which a phone connected to it can help
ascertain the phone’s approximate location at that time.
Morgan, 292 F. Supp. 3d at at 482.

     The district court, though, was not content to “accept drive
testing as reliable simply because of its similarities to historical
cell-site analysis,” Morgan, 292 F. Supp. 3d at 479. Rather,
the court assessed each step of the drive-test methodology in
substantial detail. Id. at 479–85. It did so in part to assure itself
that the government had “adequately addressed potential
sources of error in drive testing methodology.” Id. at 479. And
it concluded that “drive testing testimony is sufficiently
reliable.” Id. at 485.

     Morgan takes issue with the government’s failure to
identify independent testing or sufficient peer review of drive
testing. It is true that Daubert listed, as one factor potentially
bearing on a court’s assessment of admissibility under Rule
702, whether the technique in question “has been subjected to
                               16
peer review and publication.” 509 U.S. at 593. But the
Daubert factors “may or may not be pertinent in assessing
reliability” in specific circumstances. Kumho Tire, 526 U.S. at
150 (citation and quotation marks omitted). Of particular
relevance, it “might not be surprising in a particular case . . .
that a claim made by a scientific witness has never been the
subject of peer review.” Id. at 151.

     Here, the district court understandably declined to
“automatically exclude evidence because it is too new, or of
too limited outside interest, to generate extensive independent
research or peer-reviewed publications.” Morgan, 292 F.
Supp. 3d at 484; see also Ambrosini, 101 F.3d at 134. And the
court reasonably found that the wide acceptance of drive
testing by engineers in the wireless industry, coupled with its
use in law enforcement, offered sufficient indicia of reliability
to overcome the lack of independent studies of the relatively
newer practice. Morgan, 292 F. Supp. 3d at 484 & n.7 (citing
Daubert, 509 U.S. at 594).

     Morgan also challenges the reliability of Horan’s
testimony on the ground that Horan could not explain the
computer algorithms that processed the drive-test data and
generated the coverage maps. But we have never held that Rule
702 requires an expert to have a sophisticated understanding of
the software underlying her technological tools. Cf. United
States v. Chiaradio, 684 F.3d 265, 278 (1st Cir. 2012). If we
required expert witnesses to have detailed knowledge of the
software underlying their testimony, they could almost never
testify on matters related to proprietary technology. For
example, “anyone who testifies using any basic software such
as Excel . . . to provide financial analysis[] would be required
to be an expert in the algorithms by which Excel codes its
formula and calculations.” Nelson, 533 F. Supp. 3d at 798
(citation and quotation marks omitted).
                               17

     Federal Rule of Evidence 702 does not compel that result.
The touchstone of Rule 702 is reliability. Even if Horan could
not explain the inner workings of the software that generated
the drive-test maps, he could assure the reliability of his drive
test and the maps it generated through other means. Horan was
indisputably qualified to testify about a technological tool that
has earned wide acceptance in a relevant industry, and he used
the tool in its customary manner. His inability to explain a
proprietary algorithm did not pose a categorical bar to a finding
of reliability.

     Fourth, and finally, the district court reasonably found that
Horan “reliably applied the principles and methods to the facts
of the case.” Fed. R. Evid. 702(d). Following its step-by-step
assessment of drive-test methodology generally, the court
examined the methodology “as applied in this case” to confirm
that Horan’s testimony would be based on a reliable use of the
drive test. Morgan, 292 F. Supp. 3d at 479. The court
explained, for instance, that to produce reliable results, agents
must make sure there were no changes to the tower or cellular
network between the time of the relevant incident and the time
of the test. Id. at 480. Horan did that here. Id. Also, after the
completion of a drive test, another agent must “peer review”
the draft analysis produced by the processing program. Id. at
481–82. That process worked as it should have in this case:
Horan had “input a wrong code” during his draft analysis, “but
the peer review process corrected the error” and found no other
ones. Id. at 482. In response, Morgan makes no independent
argument under Rule 702(d) that he has not already made
elsewhere, and we have found those arguments unpersuasive
for the reasons explained.

     On the record before us—and mindful of the admonition
that “the trial judge must have considerable leeway in deciding
                              18
. . . how to go about determining whether particular expert
testimony is reliable,” Kumho Tire Co., 526 U.S. at 152—we
conclude that the district court did not abuse its discretion in
finding Horan’s testimony to be sufficiently reliable.

                              B.

     Morgan also contends that Horan’s expert testimony
should have been excluded under Rule 403. Under Rule 403,
a court “may exclude relevant evidence if its probative value is
substantially outweighed by a danger of one or more of the
following: unfair prejudice, confusing the issues, misleading
the jury, undue delay, wasting time, or needlessly presenting
cumulative evidence.” Fed. R. Evid. 403. As with Rule 702
challenges, “we review a trial judge’s application of Rule 403
for abuse of discretion.” United States v. Ring, 706 F.3d 460,
471 (D.C. Cir. 2013) (citation and quotation marks omitted).

     Horan’s testimony had significant probative value. It gave
the jury information about Morgan and J.T.’s whereabouts on
the night in question. See, e.g., Jones, 918 F. Supp. 2d at 6.
And it supported J.T.’s account that Morgan had transported
her across state lines—an essential element of the
transportation charge under 18 U.S.C. § 2423(a).

     Morgan’s primary concern was that Horan could mislead
the jury by implying he could pinpoint the precise location of
Morgan’s and J.T.’s phones. But the district court addressed
that concern by admitting Horan’s testimony “with the
qualification that [he] may not testify or imply that he can
pinpoint a person’s exact location using drive testing.”
Morgan, 292 F. Supp. 3d at 476–77. And Horan’s trial
testimony complied with that condition. He showed the jury
maps with shaded areas representing cell tower coverage, and
he testified only that the phones were located somewhere
                               19
within those large shaded zones. Horan also reiterated that he
could not “narrow [the location] down any further” than the
large colored areas. Apr. 30, 2018 Trial Tr. 167:15–16, App.
1237. To the extent Morgan believes the borders of the shaded
areas should have been characterized as imprecise or less
“definitive[],” Morgan Br. 47, the defense could have cross-
examined Horan on that point or introduced the testimony of
its own expert.

    In light of the probative value of Horan’s testimony and
the deference we afford district courts in making
determinations under Rule 403, we cannot say that the district
court here abused its discretion in allowing the jury to hear
from him.

                              III.

     We now turn to Morgan’s challenge to the jury instructions
for the transportation charge under 18 U.S.C. § 2423(a).
Section 2423(a) provides: “A person who [1] knowingly
transports an individual who has not attained the age of 18
years in interstate or foreign commerce, or in any
commonwealth, territory or possession of the United States, [2]
with intent that the individual engage in prostitution, or in any
sexual activity for which any person can be charged with a
criminal offense, shall be fined under this title and imprisoned
not less than 10 years or for life.” 18 U.S.C. § 2423(a)
(numbers in brackets added). We will refer to the first clause
as the “knowingly clause” and to the second as the “intent
clause.”

     Under the intent clause, the defendant must intend for the
transported minor to engage either in “prostitution” or in “any
sexual activity for which any person can be charged with a
criminal offense.” Id. This case involves the latter, and the
                               20
underlying “criminal offense” is section 3-307(a)(4) of the
Maryland Criminal Code. That provision bars any person who
is 21 or over from engaging in a sexual act with a victim who
is 14 or 15. Md. Code Ann., Crim. Law § 3-307(a)(4). At the
time of the offense, Morgan was 55 and J.T. was 15. It is
settled as a matter of Maryland law that, to violate section 3-
307(a)(4), the defendant need not know that the victim is under
16. See Moore v. State, 882 A.2d 256, 269 (Md. 2005).

     The district court instructed the jury that it was
unnecessary for the government to prove that Morgan knew
J.T. was underage at the time of the offense. In Morgan’s view,
the district court’s instruction was inconsistent with both the
knowingly and intent clauses of section 2423(a). With regard
to the knowingly clause, Morgan contends that the statute
required the jury to find that he knew J.T. had “not attained the
age of 18” at the time of the offense. 18 U.S.C. § 2423(a). As
for the intent clause, Morgan submits that the statute required
the jury to find that he knew J.T. was under 16, the relevant age
of consent in the incorporated Maryland “criminal offense.”
Id.

     Morgan preserved those statutory interpretation arguments
before the district court, so we review them de novo. See
United States v. Villanueva-Sotelo, 515 F.3d 1234, 1237 (D.C.
Cir. 2008). We reject them both. We conclude that, while
section 2423(a) required proof that J.T. in fact was underage
(under 18 for purposes of the knowingly clause and under 16
for purposes of the intent clause), the statute did not require
proof that Morgan knew J.T. was underage. It was enough that
Morgan knowingly transported her across state lines with the
intent that she would engage in sexual activity for which he
could be charged: sexual contact with a person under 16 by a
person 21 or over.
                               21
                               A.

     The knowingly clause of section 2423(a) covers a “person
who knowingly transports an individual who has not attained
the age of 18.” 18 U.S.C. § 2423(a). We begin by considering
whether “knowingly” requires that the defendant knew the
individual he transported was under 18 in order to be convicted
under section 2423(a). We hold that it does not.

     “Whether a criminal statute requires the Government to
prove that the defendant acted knowingly is a question of
congressional intent.” Rehaif v. United States, 139 S. Ct. 2191,
2195 (2019) (citing Staples v. United States, 511 U.S. 600, 605
(1994)). Here, the terms of section 2423(a) make plain that the
defendant must act “knowingly” when “transport[ing] an
individual.” 18 U.S.C. § 2423(a). The question is whether the
term “knowingly” also applies to the ensuing element in the
statutory text: that the transported individual “has not attained
the age of 18.” Id. Must the defendant know that the
transported individual is under 18, or is it enough if the
transported individual in fact is under 18 regardless of the
defendant’s knowledge of her age?

     In addressing that question, we “start from a longstanding
presumption, traceable to the common law, that Congress
intends to require a defendant to possess a culpable mental state
regarding ‘each of the statutory elements that criminalize
otherwise innocent conduct.’” Rehaif, 139 S. Ct. at 2195
(quoting United States v. X-Citement Video, Inc., 513 U.S. 64,
72 (1994)); accord Ruan v. United States, No. 20-1410, slip op.
at 5 (U.S. June 27, 2022). Courts “refer[] to this culpable
mental state as scienter,” Ruan, slip op. at 5 (quotation marks
omitted), and thus to the “longstanding presumption” as one
“in favor of scienter,” Rehaif, 139 S. Ct. at 2195 (quotation
marks omitted). And when a statute already “includes a
                               22
general scienter provision, the presumption applies with equal
or greater force to the scope of that provision.” Ruan, slip op.
at 6 (emphasis, quotation marks, and citation omitted). Under
the presumption, then, “a word such as ‘knowingly’ modifies
not only the words directly following it, but also those other
statutory terms that separate wrongful from innocent acts.” Id.
(quotation marks and citation omitted).

     In that context, moreover, the presumption in favor of
scienter is reinforced by the way in which courts generally
construe the reach of an adverb like “knowingly” as “a matter
of ordinary English grammar.” Flores-Figueroa v. United
States, 556 U.S. 646, 650 (2009). As relevant here, “courts
ordinarily read a phrase in a criminal statute that introduces the
elements of a crime with the word ‘knowingly’ as applying that
word to each element.” Id. at 652. Accordingly, both because
of that rule of construction and because of the way the
presumption favoring scienter operates, the word “knowingly”
in a criminal statute would typically apply to all offense
elements that follow it. If that presumptive understanding
governed in this case, “knowingly” in section 2423(a) would
apply to the offense’s under-18 element.

      Here, though, the presumptive understanding does not
control. As is true of any presumption, there can be a
“convincing reason to depart from the ordinary presumption in
favor of scienter.” Rehaif, 139 S. Ct. at 2195; see Ruan, slip
op. at 7–8. Likewise for the ordinary textual understanding of
the operation of the word “knowingly” in criminal statutes:
that understanding is “a contextual one,” subject to being
overcome in “special context[s].” Flores-Figueroa, 556 U.S.
at 652. Section 2423(a) presents just such a circumstance. In
Flores-Figueroa, in fact, Justice Alito’s concurring opinion
specifically discusses section 2423(a) as an “instance[] in
which context may well rebut [the] presumption” that a
                                23
“specified mens rea applies to all the elements of an offense.”
Id. at 660 (Alito, J., concurring in part and concurring in
judgment). As he observed, the “Courts of Appeals have
uniformly held that a defendant need not know the victim’s age
to be guilty under this statute.” Id. (citing decisions).

     The context of section 2423(a) is sex crimes involving
minors. And it is well understood, as the Flores-Figueroa
Court explained, that “many sex crimes involving minors do
not ordinarily require that a perpetrator know that his victim is
a minor.” Id. at 653. Indeed, “the common-law presumption
of mens rea . . . expressly excepted ‘sex offenses, such as rape,
in which the victim’s actual age was determinative despite
defendant’s reasonable belief that the girl had reached [the] age
of consent.’” X-Citement Video, Inc., 513 U.S. at 72 n.2
(quoting Morissette v. United States, 342 U.S. 246, 251 n.8
(1952)); see United States v. Burwell, 690 F.3d 500, 537 n.10
(D.C. Cir. 2012) (en banc) (Kavanaugh, J., dissenting) (“The
most well-known offense elements that were historically
applied in a strict liability manner [include] the victim’s age in
a statutory rape case . . . .”).

     The purpose of declining to require knowledge of the
victim’s age in the context of sex offenses involving minors is
apparent: protection of minors. Our court’s decision in a
closely related context in United States v. Chin, 981 F.2d 1275
(1992) (R.B. Ginsburg, J.), cert. denied, 508 U.S. 923 (1993),
is instructive in that regard. That case involved 21 U.S.C.
§ 861(a), which makes it a crime to “knowingly and
intentionally . . . employ, hire, use, persuade, induce, entice, or
coerce, a person under eighteen years of age to assist in
avoiding detection or apprehension for” listed federal drug
offenses. The question we faced is whether the statute’s
scienter language—“knowingly and intentionally”—applies to
the under-18 element. Chin, 981 F.2d at 1279. That is, does
                               24
the defendant need to have known that the person he hired,
used, induced, etc., was under 18? We answered that question
in the negative, reasoning that the “objective of protecting
juveniles as a class strongly indicates that Congress meant to
impose on the drug dealer the burden of inquiry and the risk of
misjudgment.” Id. at 1280. Under section 2423(a), similarly,
declining to require knowledge of the transported minor’s age
would “protect young persons who are transported for illicit
purposes, and not transporters who remain ignorant of the age
of those whom they transport.” United States v. Taylor, 239
F.3d 994, 996 (9th Cir. 2001).

     Following the course charted by our decision in Chin, we
join every court of appeals to have addressed the question in
holding that “knowingly” in section 2423(a) does not require
the defendant to know that the person transported across state
lines for criminal sexual activity was under 18. See United
States v. Tavares, 705 F.3d 4, 18–20 (1st Cir. 2013); United
States v. Griffith, 284 F.3d 338, 350–51 (2d Cir. 2002); United
States v. Tyson, 947 F.3d 139, 142–44 (3d Cir. 2020), cert.
denied, 141 S. Ct. 307 (2020); United States v. Washington,
743 F.3d 938, 941–43 (4th Cir. 2014); United States v. Daniels,
653 F.3d 399, 409–10 (6th Cir. 2011); United States v. Cox,
577 F.3d 833, 836–38 (7th Cir. 2009); United States v. Taylor,
239 F.3d 994, 997 (9th Cir. 2001); United States v. Lacy, 904
F.3d 889, 897–98 (10th Cir. 2018). That conclusion also
squares with our own court’s en banc decision in United States
v. Burwell, in which we explained that “[c]ertain statutes
involving juveniles, where the victim’s age is an element of the
offense . . . do not require proof of mens rea with respect to the
juvenile’s age.” 690 F.3d at 508. As a principal example, we
cited section 2423 and decisions construing it. Id. at 508 & n.3.

    Morgan emphasizes that the uniform line of circuit court
decisions (as well as our court’s observation in Burwell)
                                25
“addressed the issue in the context of transport of a minor for
prostitution—a crime with its own mens rea.” Morgan Br. 68;
see Burwell, 690 F.3d at 508 (describing section 2423 as
“prohibiting transportation of juveniles across state lines for the
purpose of prostitution”). Recall, in this regard, that section
2423(a) prohibits “knowingly transport[ing] an individual who
has not attained the age of 18” to engage either “in prostitution”
or “in any sexual activity” carrying a criminal charge. 18
U.S.C. § 2423(a). When the underlying crime is prostitution,
Morgan reasons, the defendant is aware of the facts rendering
the intended conduct wrongful by virtue of his intent that
prostitution occur. But when the underlying crime is strict-
liability sexual activity with a minor, he continues, the
defendant may not know the fact rendering his conduct
wrongful: that the transportee is under 18. In the latter
situation, Morgan thus posits, requiring knowledge of the
transportee’s under-18 status would “advance the purpose of
scienter”—“to separate wrongful from innocent acts”—by
requiring a defendant to be on notice of the facts rendering his
intended conduct criminal. Rehaif, 139 S. Ct. at 2197.

    The upshot of Morgan’s argument, however, cannot be
squared with the statutory text. Section 2423(a) bars
“knowingly” transporting a person “who has not attained the
age of 18” to engage either in prostitution or some other
criminal sexual activity. Under the structure of the provision,
“knowingly” applies in a constant manner regardless of the
underlying offense. There is no plausible reading under which
“knowingly” does not require knowledge of under-18 status
when the underlying offense is “prostitution” but does require
knowledge of that status when the underlying offense is other
criminal “sexual activity”—much less that the statute requires
knowledge of under-18 status only in that subset of other
“sexual activity” involving strict-liability sexual crimes against
minors. The statute works in an all-or-nothing fashion: it
                               26
requires knowledge of under-18 status either for all underlying
offenses or for none. And if it does not require knowledge that
the transported person is under 18 in cases involving
prostitution—as the circuits have uniformly held—it also does
not require knowledge in cases involving other criminal sexual
activity (including strict-liability sexual conduct with a minor).

    At any rate, even if we look solely to circumstances in
which the underlying offense is strict-liability sexual activity
with a minor, applying the word “knowingly” to section
2423(a)’s under-18 element still cannot be the key to separating
“wrongful from innocent acts.” Rehaif, 139 S. Ct. at 2197. The
broader statutory context demonstrates why.

      A nearby provision, section 2421, defines an essentially
identical transportation crime except that it contains no
requirement concerning the transportee’s age: “Whoever
knowingly transports any individual in interstate or foreign
commerce . . . with intent that such individual engage in
prostitution, or in any sexual activity for which any person can
be charged with a criminal offense . . . shall be fined under this
title or imprisoned not more than 10 years, or both.” 18 U.S.C.
§ 2421. Sections 2421 and 2423(a) thus work in tandem in that
they prohibit the same acts of transportation to engage in sexual
crimes, but with the potential sentence rising from a maximum
of 10 years (section 2421) to a minimum of 10 years (section
2423(a)) if the transportee is under 18. Because section 2421
operates as a lesser-included offense of section 2423(a),
applying the word “knowingly” to the under-18 element in
section 2423(a) would not separate wrongful from otherwise
innocent conduct. Rather, any conduct within the compass of
section 2423(a) is already a felony under section 2421.

     To be sure, section 2423(a) markedly increases the
potential sentence for that conduct if the transportee is under
                               27
18. But Congress made clear in section 2423 itself that it saw
no issue with a substantial sentencing increase for a sexual
offense when the victim is under 18, even if the defendant does
not know (or has a mistaken belief about) the victim’s under-
18 status. Explaining the point requires working through an
intricate set of nested provisions.

     The starting point is section 2423(b), the immediately
neighboring provision of section 2423(a). Section 2423(b)
makes it a felony punishable by up to 30 years of imprisonment
for a person to “travel[] in interstate commerce . . . with a
motiving purpose of engaging in any illicit sexual conduct with
another person.” 18 U.S.C. § 2423(b). And “illicit sexual
conduct” means certain defined sexual acts “with a person
under 18 years of age,” id. § 2423(f), including “a sexual act”
that would violate federal law if it “occurred in the special
maritime and territorial jurisdiction of the United States,” id.
§ 2423(f)(1), or “any commercial sex act,” id. § 2423(f)(2).
Congress specified that, in the latter category, there is a
mistake-of-age defense if the defendant can show by clear and
convincing evidence that he “reasonably believed that the
person with whom [he] engaged in the commercial sex act had
attained the age of 18 years.” Id. § 2423(g).

     Congress did not provide for such a defense, though, if the
underlying offense falls under section 2423(f)(1). As an
example, there would be no mistake-of-age defense if the
defendant traveled across state lines to engage in coerced
sexual activity with a person who (unbeknownst to the
defendant) was under 18, say, by administering an intoxicant
that would temporarily impair the victim’s mental capacity.
See id. §§ 2241(b), 2423(b), 2423(f)(1). In that situation, based
solely on the victim’s under-18 status, the defendant would go
from someone who has not committed a federal offense at all
(because there is no analog to section 2423(b) for victims who
                               28
are over 18), to someone who has committed a felony subject
to a 30-year sentence—even if the defendant had no knowledge
of the victim’s actual age. If the travel offense under section
2423(b) operates in that fashion, it stands to reason that the
neighboring transportation offense under section 2423(a)
likewise carries a substantial sentence when the victim is under
18, regardless of whether the defendant knows the victim’s age.

     If Congress nonetheless wanted section 2423(a) to
function differently so as to require knowledge that the
transportee is under 18, it could have made its intention clear
by framing the text to cover a person “who knowingly
transports an individual, knowing that the individual has not
attained the age of 18,” rather than speaking in terms of a
“person who knowingly transports an individual who has not
attained the age of 18.” Id. § 2423(a). Congress employed
precisely the former kind of formulation in a close-by
provision, section 2425, which makes it a crime to “knowingly
initiate[] transmission of [identifying information] of another
individual, knowing that such other individual has not attained
the age of 16 years, with the intent to entice, encourage, offer,
or solicit any person to engage in any sexual activity for which
any person can be charged with a criminal offense.” Id. § 2425
(emphasis added).

    Congress did not include that kind of language in section
2423(a). Absent such a specification, for the reasons we have
set out, we think “knowingly” in that provision is best
understood not to apply to its under-18 element.

                               B.

    Having addressed Morgan’s argument under Section
2423(a)’s knowingly clause, we next consider his argument
under the provision’s intent clause. As applied in this case, that
                               29
clause covers transportation of a minor “with intent that the
individual engage in . . . any sexual activity for which any
person can be charged with a criminal offense.” 18 U.S.C.
§ 2423(a). Morgan contends that, when the underlying
“criminal offense” is statutory rape, the word “intent” means
that the defendant must know that the victim’s age fell below
the age of consent (which here is 16). We disagree.

     The most natural reading of the intent clause calls for a
two-step inquiry: first, did the defendant transport the minor
“with intent” for her to engage in “sexual activity”? Second, if
the intended sexual activity were to occur, could anyone be
“charged with a criminal offense” for it? That second step
renders section 2423(a) a “piggyback offense.” United
States v. Ray, 831 F.3d 431, 434 (7th Cir. 2016). It is not
enough that the defendant intends for just any sexual activity
to take place; “the prosecution must show that the [intended]
sexual activity . . . violated [or would have violated] some other
statute.” Id.; accord United States v. Cotto-Flores, 970 F.3d
17, 36–37 (1st Cir. 2020).

     Applying that two-step approach here, we conclude that
the jury need not have found that Morgan knew J.T. was under
16 to convict him on the transportation charge. At step one of
the inquiry, the jury concluded that Morgan intended for J.T. to
engage in sexual activity with him when he drove her to
Maryland. At step two, the question is whether that intended
sexual activity was something for which a “person can be
charged with a criminal offense.” The answer is yes. The
Maryland Criminal Code makes it unlawful for a person 21 or
over (like Morgan) to engage in a sexual act with someone
under 16 (like J.T.). Md. Code Ann., Crim. Law § 3-307(a)(3),
(4). And because the Maryland crime “has no . . . mens rea
element with regard to the victim’s age,” Moore v. State, 882
A.2d 256, 269 (Md. 2005) (quotations omitted), section
                               30
2423(a)’s intent clause—true to its piggyback nature—does not
have one, either: the intended sexual activity “can be charged
[as] a criminal offense” (in Maryland) regardless of whether
Morgan knew J.T. was under 16 years old. 18 U.S.C. §
2423(a).

     In resisting that understanding, Morgan says that the
relevant question under section 2423(a)’s intent clause is
whether the defendant intends to engage in criminal sexual
activity (i.e. sexual activity for which a person can be charged
with a criminal offense). And when the underlying offense is
statutory rape, Morgan submits, section 2423(a)’s intent clause
requires that the defendant know the victim is underage:
otherwise, it cannot be said that the defendant intends to engage
in criminal sexual activity. After all, Morgan reasons, the
victim’s age is what renders criminal an otherwise lawful
sexual act.

     For Morgan’s interpretation to work, however, the
following would need to be true: even if (a) the defendant has
an intent that the transported minor engage in sexual activity,
and even if (b) that sexual activity is conduct for which a person
can be charged with a criminal offense, it nonetheless is untrue
that (c) the defendant has an “intent” that the transported minor
“engage in . . . sexual activity for which any person can be
charged with a criminal offense.” 18 U.S.C. § 2423(a). Given
that (c) is just a verbatim agglomeration of (a) and (b), the
notion that (c) could be untrue even if (a) and (b) were true is,
at the least, an uneasy fit with the statutory text. And here, (a)
and (b) are both true.

     On that score, because Morgan does not appear to contest
the truth of (a), his only point of disagreement presumably
concerns (b). That is, Morgan would have to submit that (b)
could not be true here unless he knew J.T. was under the age of
                               31
16. But when, as in this case, the sexual activity at issue is
covered by a strict-liability offense, that activity by definition
is conduct for which a “person can be charged with a criminal
offense” as long as the victim was in fact below the age of
consent—regardless of the defendant’s knowledge of the
victim’s underage status. So, (b) is satisfied here. Both (a) and
(b) are thus true, in which case (c) should be as well.

     Morgan might also resist the framing of (b) in that, in his
view, the pertinent question is not just whether the intended
sexual activity would be criminally chargeable, but is whether
the defendant intended that the intended sexual activity would
be criminally chargeable. That rationale would rest on reading
the word “intent” in the statute to modify not only the adjacent
phrase, “to engage in . . . sexual activity,” but also the ensuing
phrase, “for which any person can be charged with a criminal
offense.” 18 U.S.C. § 2423(a).

      We, however, read the word “intent” to modify “engage in
. . . sexual activity” but not to reach “for which any person
could be subject to a criminal charge.” We do so for largely
the same reasons that, under the knowingly clause, we read the
word “knowingly” to modify “transports an individual” but not
to reach “who has not attained the age of 18”: when the context
is sex offenses involving minors, general canons and
presumptions about mens rea in criminal statutes are
inapplicable to the element of underage status, in service of the
interest in protecting minors. See Flores-Figueroa, 556 U.S.
at 653; X-Citement Video, Inc., 513 U.S. at 72 n.2; Burwell, 690
F.3d at 537 n.10 (Kavanaugh, J., dissenting); Chin, 981 F.2d at
1279–80. (As an aside, we note that Morgan’s reading in fact
rests on more than concluding that “intent” modifies “for which
any person could be subject to a criminal charge,” in that he
would ask whether the defendant knows (as opposed to intends)
that the sexual activity would be chargeable. Morgan Br. 58.
                               32
But because we conclude that “intent” does not reach “for
which any person could be subject to a criminal charge,” we
need not consider whether “intends” and “knows” would carry
essentially the same meaning in this specific situation.)

     Morgan’s interpretation of the intent clause, moreover, is
difficult to square with the broader structure of the statute.
Recall that the neighboring provision, section 2423(b),
prohibits traveling across state lines “with a motivating purpose
of engaging in any illicit sexual conduct with another person,”
where “illicit sexual conduct” is defined to include certain
sexual acts “with a person under 18.” Id. § 2423(b), (f)(1)–(2).
If we assume that “a motivating purpose” is essentially
synonymous with an “intent”—and, in fact, the title of section
2423(b) is “Travel with intent to engage in illicit sexual
conduct,” id. (emphasis added)—then the operation of section
2423(b) parallels the operation of section 2423(a)’s intent
clause as applied to statutory rape: both provisions prohibit the
taking of an act (transportation or travel) while having an intent
(or motivating purpose) that someone engage in criminal/illicit
sexual activity, where the criminal/illicit nature of the sexual
activity turns on the victim’s underage status.

      Under Morgan’s argument, he could not have intended for
J.T. to engage in criminal sexual activity for purposes of
section 2423(a)’s intent clause unless he knew J.T. was
underage. But under section 2423(b), incongruously, Congress
made clear that a defendant can have an intent to engage in
illicit sexual activity even if he does not know the victim is
underage. We know this because Congress established a
reasonable-mistake-of-age defense for certain applications of
section 2423(b). See 18 U.S.C. § 2423(g). And there could be
no reason to enact a reasonable-mistake-of-age defense if the
government were required to prove knowledge of age in the
first place. The result is that a defendant can have an intent to
                               33
engage in illicit sexual conduct under section 2423(b)
regardless of whether he knows the victim’s underage status,
even when that status is what makes the conduct illicit for
purposes of section 2423(b). See id. § 2423(f). Assuming
Congress would envision parallel and neighboring provisions
to work in parallel ways, section 2423(b) suggests that a
defendant likewise can have an intent to engage in criminal
sexual activity under section 2423(a)’s intent clause regardless
of whether he knows the victim’s underage status, even when
(as in this case) that status is what makes the activity criminal.

     That interpretation is reinforced by the intent clause’s
statutory purpose. In framing the clause to encompass
transportation of a minor to engage in “any sexual activity”
chargeable as “a criminal offense,” id. § 2423(a), Congress
criminalized transportation for “illegal sexual activity under
any applicable law—Federal, State or local.” H.R. Rep. No.
99-910, at 8 (1986) (emphasis added). And in structuring the
intent clause in that way, Congress conformed the federal
prohibition against transportation for criminal sexual activity
to the relevant “community standards regarding acceptable
sexual behavior.” Id. Congress, that is, sought to fortify
community standards about permissible sexual behavior by
barring transportation into a state for sexual activity that would
violate that state’s laws.

     Here, that state is Maryland. And section 3-307(a)(4) of
the Maryland Criminal Code codifies a strict community
standard for acceptable sexual behavior. Maryland determined
that individuals who are 21 or over commit a felony by
engaging in sexual conduct with anyone under 16, Md. Code
Ann., Crim. Law §§ 3-304(a)(3), 3-307(a)(4), regardless of
whether the adult knows the minor’s age, see Moore, 882 A.2d
at 269. Section 3-307(a)(4) thereby embodies Maryland’s
judgment that, to adequately protect minors, it is acceptable—
                               34
and indeed necessary—to criminalize sexual contact by an
adult with someone under 16 even if the adult is unaware of the
victim’s underage status. In section 2423(a), Congress sought
to incorporate Maryland’s understanding of acceptable sexual
behavior in circumstances in which a person transports a minor
into that state to engage in sexual activity there. Morgan’s
interpretation, though, would do the opposite, denying
Congress’s evident purpose to give effect to Maryland’s
community standards for acceptable sexual behavior by
criminalizing the transport of minors into the state to engage in
sexual activity there that the state deems a crime.

     Morgan responds by asserting that the Maryland Court of
Appeals has declined to recognize a common-law crime of
attempted violation of section 3-307(a)(4) of the Maryland
Criminal Code. See Moore, 882 A.2d at 268–70; but see
Maxwell v. State, 895 A.2d 327, 334 (Md. Spec. App. 2006)
(limiting Moore). Morgan further notes that section 2423(a),
like an attempt charge, does not require completion of the
underlying offense. In that light, Morgan suggests, it would be
more consistent with Maryland’s standards to deny the
application of section 2423(a) to that state’s strict-liability
offenses unless there is a requirement to prove a defendant’s
knowledge of underage status.

     It is far from clear that Morgan’s understanding of
Maryland attempt law is correct, see Maxwell, 895 A.2d at 334,
but even assuming it is, Morgan’s reasoning is misconceived.
While both section 2423(a) and a state-law attempt charge
concern steps undertaken on the way to completing an
underlying sex crime, Congress made an independent
judgment that, regardless of the contours of a given state’s
attempt law, there is a strong federal interest in establishing a
strict federal criminal bar against transporting a minor to
engage in sexual activity that would violate state law if
                                35
completed. True, the scope of the underlying sex offense is
defined by state law, and Congress sought to respect a state’s
own standards of what is acceptable (and impermissible) in that
important regard. But once the scope of the underlying state-
law offense is given effect, section 2423(a)’s ban on
transporting a minor to engage in that state-law offense is an
independent—and serious—federal wrong. No one could
suggest, for instance, that if a state opted to do away entirely
with attempt charges for sex crimes, then section 2423(a)
somehow would cease to operate altogether against
transportation of a minor to engage in a sex crime in that state.
Nor could anyone suggest that, if a state penalizes attempt to
engage in a sex crime with a minor less strictly than does
section 2423(a), then the available federal sentence somehow
would be capped in a commensurate manner.

     Additionally, even if the shape of a state’s attempt law did
have bearing on the meaning of “intent” under section 2423(a),
there would be a significant mismatch between Morgan’s
reasoning and his remedy. Morgan would allow a section
2423(a) charge when the underlying state-law crime falls under
section 307(a)(4) of the Maryland Criminal Code but would
require the jury to find knowledge of the victim’s underage
status. Morgan makes no suggestion, though, that his proposed
approach maps onto anything in existence under Maryland law.
Maryland does in fact criminalize antecedent steps tied to a
violation of section 3-307(a)(4) in certain circumstances, see
Md. Code Ann., Crim. Law § 3-324(b), but Morgan does not
purport to conform his interpretation of section 2423(a) to that
offense. Indeed, Morgan’s approach would affirmatively
contradict state attempt law in some situations: his approach
would impose a blanket requirement to prove knowledge of
underage status under section 2423(a) when the underlying
crime is a strict-liability offense, even if the relevant state’s
laws contain an attempt offense that operates in a strict-liability
                               36
fashion as to age. See, e.g., State v. Sines, 579 S.E.2d 895, 900
(N.C. App. Ct. 2003).

     The purpose of section 2423(a)’s intent clause, in short, is
to incorporate a state’s standards of what is acceptable sexual
behavior, not to mirror a state’s decisions about the scope of its
attempt law. With that understanding in mind, Morgan’s
reading of the intent clause conflicts with Maryland’s relevant
judgments (and those of Congress).

                           *    *   *

      The statutory text, structure, and purpose all point to the
same conclusion about the proper interpretation of section
2423(a)’s intent clause as applied to this case: Morgan
transported J.T. across state lines “with intent that [she] engage
in . . . sexual activity for which [he could] be charged with a
criminal offense,” regardless of whether he knew she was
under 16. 18 U.S.C. § 2423(a). And as we determined earlier
in the context of the provision’s knowingly clause, Morgan also
“knowingly transport[ed] an individual who has not attained
the age of 18,” regardless of whether he knew J.T. was under
18. Id.

     In a last argument, Morgan contends that, even if section
2423(a) can be read in that way, the rule of lenity should tip the
balance in favor of his contrary interpretation. We think,
however, that there is no “grievous ambiguity” here of the sort
that would bring lenity principles into play. E.g., Ocasio v.
United States, 578 U.S. 282, 295 n.8 (2016). Significantly, our
court reached that conclusion in United States v. Chin, which,
as explained, involved a related criminal offense that likewise
turns on a person’s status as a minor, 18 U.S.C. § 861(a). In
holding that the statute did not require proof that the defendant
had knowledge of the minor’s age, we rejected the defendant’s
                               37
reliance on the rule of lenity. Chin, 981 F.2d at 1280. We
explained that “the requisite legislative intent,” even if
“imperfectly expressed,” was “fairly implied” to an adequate
extent that resort to lenity principles was unjustified. Id. We
conclude the same here.

     We note, finally, one issue we need not reach. In arguing
that section 2423(a) is best read to require proof that he knew
J.T.’s underage status, Morgan highlights various factual
scenarios in which there may be no face-to-face interaction
between the defendant and the transported minor (for instance,
if the defendant commissions the transport of a minor without
directly participating in it). In those sorts of situations, the
possibility of a reasonable mistake about the victim’s age may
be enhanced because the defendant might never lay eyes on the
victim.

     There is no occasion for us to treat with such
circumstances in this case because Morgan met J.T. in person
and interacted with her before transporting her across state
lines. Morgan thus could not (and does not) make any
argument that his conduct should fall outside the ambit of
section 2423(a) due to the lack of face-to-face engagement with
J.T. And as a result, we have no occasion to consider whether
those kinds of circumstances might conceivably be distinct in
some fashion that could matter under the statute in cases
involving strict-liability offenses.

     In X-Citement Video, Inc., the Supreme Court indicated
that there may be a lesser need to give effect to the “common-
law presumption of mens rea” in circumstances in which “the
perpetrator confronts the underage victim personally and may
reasonably be required to ascertain that victim’s age.” 513 U.S.
at 72 n.2; see id. at 76 n.5; United States v. Robinson, 702 F.3d
22, 32 (2d Cir. 2012) (“But that presumption [of mens rea] does
                               38
not apply to sex crimes against minors, at least ‘when the
perpetrator confronts the underage victim personally.’”
(citation omitted) (quoting X-Citement Video, Inc., 513 U.S. at
72 n.2)); cf. 18 U.S.C. § 1591(c) (providing that the
government “need not prove that the defendant knew . . . that
[a sex-trafficking victim] had not attained the age of 18” if “the
defendant had a reasonable opportunity to observe the
person”). We have no reason here to consider the potential
salience (if any) of that logic in the perhaps unlikely event that
the government would pursue a section 2423(a) charge against
someone who had no in-person interactions with the minor and
whose underlying sex offense is a strict-liability one. This case
does not involve that situation, and in the circumstances at
hand, we find no error in the district court’s instruction to the
jury that it need not find Morgan knew of J.T.’s underage status
to find him guilty of violating section 2423(a).

                               IV.

     Morgan briefly raises a final challenge that he
acknowledges is foreclosed by Supreme Court precedent. He
contends that his convictions based on SORNA registration
obligations are predicated upon an unconstitutional delegation
of legislative authority to the Attorney General. The Supreme
Court rejected that precise challenge in Gundy v. United States,
139 S. Ct. 2116, 2121–24 (2019). Morgan concedes as much,
explaining that he raises the argument only to preserve his
ability to argue to the Supreme Court that it should reconsider
Gundy and adopt the position advanced by the dissent in that
case. He remains free to do so, but for purposes of our court,
we must reject his argument based on Gundy.
                             39
                     *   *   *    *   *

     For the foregoing reasons, we affirm the judgment of the
district court.

                                                 So ordered.