PRECEDENTIAL
UNITED STATES COURT OF APPEALS
FOR THE THIRD CIRCUIT
_____________
No. 18-3804
_____________
UNITED STATES OF AMERICA
v.
WILLIAM M. TYSON,
Appellant
______________
Appeal from the United States District Court
for the Middle District of Pennsylvania
(D.C. No. 1-17-cr-00316-001)
District Judge: Honorable Christopher C. Conner
______________
Argued: September 11, 2019
______________
Before: CHAGARES, JORDAN, and RESTREPO,
Circuit Judges.
(Filed: January 14, 2020)
______________
John A. Abom [Argued]
Abom & Kutulakis, LLC
2 West High Street
Carlisle, PA 17013
Counsel for Appellant
David J. Freed
William A. Behe
United States Attorney’s Office
228 Walnut Street, Suite 220
Harrisburg, PA 17101
Francis P. Sempa [Argued]
United States Attorney’s Office
235 North Washington Avenue
P.O. Box 309, Suite 311
Scranton, PA 18503
Counsel for Appellee
______________
OPINION OF THE COURT
______________
RESTREPO, Circuit Judge.
William Tyson was indicted for the transportation of a
minor to engage in prostitution and the production of child
pornography in violation of 18 U.S.C. § 2423(a) and 18 U.S.C.
§ 2251(a), respectively. During pre-trial proceedings, the
District Court granted the Government’s motion in limine to
exclude mistake-of-age evidence. Tyson and the Government
2
then submitted a conditional plea agreement preserving his
right to appeal the District Court’s order. The District Court
sentenced Tyson to concurrent terms of 180 months’
imprisonment for each count.
Tyson appeals the District Court’s grant of the
Government’s motion in limine precluding him from
introducing mistake-of-age evidence at trial. He argues that the
District Court erred in precluding the evidence because
knowledge of age is an element of § 2423(a) and § 2251(a). He
also urges us to read an affirmative defense on lack of
knowledge into each statute. We disagree. The statutes’ text,
context, and history make it clear that knowledge of age is not
an element and mistake of age is not a defense. Therefore, we
will affirm the District Court’s order.
I.
In August 2017, Tyson contacted a seventeen-year-old
female on Facebook to engage her in prostitution. After
communicating for several days via Facebook and text
messages, Tyson traveled from Pennsylvania to New York
City. Tyson picked up the victim and her friend and brought
them to Harrisburg, Pennsylvania. He then rented several
rooms at a Motel 6 in New Cumberland, Pennsylvania between
August 15 and August 20, 2017. Phone records reveal that
Harrisburg-area individuals contacted the victim to engage in
commercial sexual activity.
On August 22, 2017, after a relative of Tyson brought
the victim to a Quality Inn in New Cumberland, FBI agents and
local law enforcement recovered her during a sting operation.
Investigators interviewed her and reviewed her phone. They
3
found an August 20, 2017 video of the victim performing oral
sex on an adult male in a Motel 6 room. The victim identified
the man in the video as “Real,” whom the investigators
identified as Tyson.
On October 18, 2017, Tyson was indicted for
knowingly transporting a minor to engage in prostitution in
violation of § 2423(a) and producing child pornography in
violation of § 2251(a). Before trial, the Government filed a
motion in limine to prohibit Tyson “from eliciting evidence to
establish ‘mistake of age’” and from asserting “mistake of age”
as an affirmative defense. App. 21. The District Court granted
the motion on July 11, 2018. The Court found that evidence of
mistake of age is irrelevant to § 2423(a) and § 2251(a) because
the statutes do not require proof of defendants’ knowledge that
the victim was a minor. As a result, the Court excluded the
evidence because “its probative value is substantially
outweighed by a risk that the evidence will result in unfair
prejudice, confuse the issues, or mislead the jury” under
Federal Rule of Evidence 403. See App. 10.
Tyson and the Government subsequently entered a plea
agreement. According to its terms, Tyson and the Government
agreed to recommend to the District Court that the sentences
be served concurrently for a total of 180 months’
imprisonment. The agreement also preserved Tyson’s right to
appeal the District Court’s July 11, 2018 order granting the
Government’s motion in limine. On December 19, 2018, the
District Court sentenced Tyson to 180 months’ imprisonment
for each count, to be served concurrently. Tyson filed a Notice
of Appeal with this Court on December 24, 2018 challenging
the District Court’s order.
4
II.
The District Court had jurisdiction pursuant to 18
U.S.C. § 3231. We have jurisdiction under 28 U.S.C. § 1291
and 18 U.S.C. §3742(a).
This Court reviews decisions on the admissibility of
evidence for abuse of discretion. United States v. Higdon, 638
F.3d 233, 238 (3d Cir. 2011). District court conclusions on
whether “the risk of unfair prejudice does not substantially
outweigh the probative value of otherwise admissible
evidence” are reviewed under the same standard. Id. We
exercise plenary review over legal questions and district court
rulings based on interpretations of the Federal Rules of
Evidence. See United States v. Schiff, 602 F.3d 152, 160–61
(3d Cir. 2010); United States v. Serafini, 233 F.3d 758, 768
n.14 (3d Cir. 2000). Statutory construction determinations are
reviewed de novo. United States v. Cochran, 17 F.3d 56, 57
(3d Cir. 1994) (en banc).
III.
Tyson posits that the District Court erred in prohibiting
evidence related to mistake of age because § 2423(a) and §
2251(a) require knowledge that the victim was a minor to find
a defendant guilty. He characterizes knowledge of age as an
element of each statute. Tyson points to title 18, section 5902
of the Pennsylvania Statutes and Consolidated Statutes to
suggest that Pennsylvania law provides a mistake-of-age
defense to a prosecution based on § 2423(a). Tyson also turns
to a Ninth Circuit decision interpreting § 2251(a) to require a
mistake-of-age defense to correct the statute’s supposed
constitutional deficiencies. We disagree and join the
5
overwhelming majority of our sister circuits holding that
mistake of age is not a defense and knowledge of the victim’s
age is not required for a conviction under either § 2423(a) or §
2251(a). Thus, the District Court did not err in prohibiting
Tyson from asserting a mistake-of-age defense under Federal
Rule of Evidence 403.1
A.
The grand jury indicted Tyson for “knowingly
transport[ing] [the victim], an[] individual who had not
attained the age of 18 years, in interstate commerce, with the
intent that [the victim] engage in prostitution” in violation of §
2423(a). App. 15. The statute provides:
A person who 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, with the 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.
§ 2423(a) (emphasis added). The District Court agreed with the
Government’s position that Tyson need not have known the
1
“The 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.
6
victim’s age in order to have knowingly transported a minor.
Tyson argues that the Government must prove the defendant’s
knowledge of the victim’s age under § 2423(a). He points to
the presumption that the mens rea requirement generally
extends to each element of a criminal statute.
In Flores-Figueroa v. United States, the Supreme Court
explained that “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.” 556 U.S.
646, 652 (2009).2 Even though the mens rea typically applies
to all the elements, the majority recognized the existence of
special contexts where courts may deviate from that general
presumption. See id.
Concurring, Justice Alito elaborated on examples of
special contexts that rebut the general presumption. He
specifically mentioned § 2423(a) as an example of a statute that
calls for a contextual approach to statutory interpretation and
added that circuit courts “uniformly [hold] that a defendant
need not know the victim’s age to be guilty under [§2423(a)].”
Id. at 660 (Alito, J., concurring). The Flores-Figueroa majority
referenced Justice Alito’s concurrence with apparent approval.
Id. at 652 (noting that sentences where “knowingly” only
2
At issue in Flores-Figueroa was whether the term
“knowingly” applies to all the elements in 18 U.S.C. §
1028A(a)(1). The statute imposes a two-year sentence on
individuals who “knowingly transfer[], possess[], or use[],
without lawful authority, a means of identification of another
person” during the commission of statutorily-defined felonies.
§ 1028A(a)(1).
7
modifies a “transitive verb . . . typically involve special
contexts . . . [a]s Justice ALITO notes, the inquiry into a
sentence’s meaning is a contextual one”). Tyson does not
provide a compelling reason for us to disregard Justice Alito’s
concurrence and the majority’s recognition that the general
presumption does not apply in all contexts.
An overwhelming number of our sister circuits that
have considered § 2423(a)—both prior to and after Flores-
Figueroa—have concluded that “knowingly” does not extend
to the victim’s age.3 Interpreting a predecessor of § 2423(a),
this Court held that “[t]he statute does not state or require
knowledge of the victim’s age.” United States v. Hamilton, 456
F.2d 171, 173 (3d Cir. 1972) (per curiam). While Tyson is
correct that Hamilton is not controlling authority as to the
current statutory provision, in light of Flores-Figueroa, we are
unconvinced that we should alter our approach.
Arguing that the background presumption articulated in
Flores-Figueroa applies to § 2423(a), Tyson ignores
Congress’s clear intent that knowledge of age not be required
for a conviction pursuant to the statute. Our role in interpreting
statutes is to “give effect to Congress’s intent.” Idahoan Fresh
3
See, e.g., United States v. Lacy, 904 F.3d 889 (10th
Cir. 2018); United States v. Washington, 743 F.3d 938 (4th Cir.
2014); United States v. Tavares, 705 F.3d 4 (1st Cir. 2013);
United States v. Daniels, 653 F.3d 399 (6th Cir. 2011); United
States v. Cox, 577 F.3d 833 (7th Cir. 2009); United States v.
Griffith, 284 F.3d 338 (2nd Cir. 2002); United States v. Taylor,
239 F.3d 994 (9th Cir. 2001); see also United States v. Daniels,
685 F.3d 1237 (11th Cir. 2012) (per curiam) (discussing §
2423(a) while interpreting 18 U.S.C. § 2422(b)).
8
v. Advantage Produce, Inc., 157 F.3d 197, 202 (3d Cir. 1998).
“We . . . look to statutory context for evidence of congressional
intent.” United States v. Merlino, 785 F.3d 79, 92 (3d Cir.
2015). In considering statutory context, courts interpret statutes
in accordance with their overall scheme. Gundy v. United
States, 139 S. Ct. 2116, 2126 (2019).
Congress did not intend to require knowledge of a
victim’s age for a conviction under § 2423(a). Congress’s
purpose in enacting and amending § 2423(a) was to provide
minors special protection against sexual mistreatment. See
Taylor, 239 F.3d at 997 (citing H.R. Rep. No. 105–557 (1998)).
In the face of longstanding consensus among circuit courts that
knowledge of age is not an element of § 2423(a), Congress has
not added language to the statute “requir[ing] the government
to establish the defendant’s knowledge of the alleged victim’s
age.” United States v. Jones, 471 F.3d 535, 539 (4th Cir. 2006)
(noting that Congress amended 18 U.S.C. § 2423 nine times
between 1978 and 2006). By not extending the mens rea
requirement to the victim’s age, Congress eliminated
offenders’ opportunity to prey on children without
consequence by claiming ignorance of the victim’s age. Id. at
540. A contrary interpretation would frustrate congressional
intent to provide minors with heightened protection against
sexual exploitation.
The statute is best understood as establishing age as an
aggravating factor that subjects defendants to increased
penalties for conduct that is already prohibited under 18 U.S.C.
§ 2421.4 Aside from § 2423(a)’s focus on minors, § 2421 and
4
Section 2421 criminalizes “knowingly transport[ing]
any individual in interstate or foreign commerce . . . with intent
9
§ 2423(a) are nearly identical. Cox, 577 F.3d at 837. As a
result, those who transport individuals of any age across state
lines to engage in prostitution are “already on notice that [they
are] committing a crime.” Griffith, 284 F.3d at 351. Section
2423(a) places the risk on perpetrators that the person they
transport is a minor. Taylor, 239 F.3d at 977 (“As Congress
intended, the age of the victim simply subjects the defendant
to a more severe penalty in light of Congress’ concern about
the sexual exploitation of minors.”). Requiring knowledge of
age for a conviction under § 2423(a) would make it more
difficult to prove sexual exploitation of a minor than an adult.
See Washington, 743 F.3d at 942; Jones, 471 F.3d at 539; see
also United States v. Fontaine, 697 F.3d 221, 227–28 (3d Cir.
2012) (emphasizing that courts avoid absurd conclusions when
interpreting statutes). Because knowledge of a minor’s age is
not an element of § 2423(a), the lack of knowledge cannot be
a defense.
Tyson alternatively suggests that mistake of age is an
affirmative defense to § 2423(a). However, the statute’s
language does not create an affirmative mistake-of-age
defense. Instead, § 2423 limits a mistake-of-age defense to a
prosecution for a commercial sex act as defined in 18 U.S.C. §
2423(f)(2). Id. § 2423(g) (“In a prosecution under this section
based on . . . subsection (f)(2), it is a defense . . . that the
defendant reasonably believed that the person with whom the
defendant engaged in the commercial sex act had attained the
age of 18 years.”). Section 2423(a) does not contain
comparable language. The fact that Congress included a
mistake-of-age defense for one subsection but not another
that such individual engage in prostitution, or in any [criminal]
sexual activity.”
10
indicates that Congress intended to limit the defense to the
particular circumstance in § 2423(f)(2).
Tyson next argues that § 2423(a) produces a piggyback
offense requiring the Government to prove that he violated
some other state or federal law. He suggests that we consider
Pennsylvania’s law criminalizing prostitution of a minor. See
18 Pa. Stat. and Cons. Stat. Ann. § 5902(b.1)(3) (defining
“knowingly promot[ing] prostitution of a minor”—including
“encouraging, inducing or otherwise intentionally causing a
minor to become or remain a prostitute”—as a third degree
felony). Tyson invokes Pennsylvania law to claim that it
provides a mistake-of-age defense and therefore, a mistake-of-
age defense to a charge under § 2423(a).5
We do not adopt Tyson’s approach for two reasons.
First, as the District Court noted, § 2423(a) criminalizes two
categories of offenses: (1) engaging in prostitution and (2)
engaging in any other sexual activity prohibited by state or
federal law. Tyson was indicted on a prostitution charge rather
than under the catch-all category.6 Adopting Tyson’s approach
5
Tyson cites to statutory language providing that
“[w]hen criminality depends on the child’s being below a
critical age older than 14 years, it is a defense for the defendant
to prove by a preponderance of the evidence that he or she
reasonably believed the child to be above the critical age.” 18
Pa. Stat. and Cons. Stat. Ann. § 3102.
6
Tyson evokes the Seventh Circuit’s recognition that
“Section 2423(a) creates a piggyback offense” requiring the
Government to “show that the sexual activity after crossing the
state line violated some other statute.” United States v. Ray,
11
would deprive the term “prostitution” of meaning since §
2423(a) already prohibits sexual activity that constitutes a
criminal offense. See Duncan v. Walker, 533 U.S. 167, 174
(2001) (“[A] statute ought . . . to be so construed that . . . no
clause, sentence, or word shall be superfluous, void, or
insignificant.”).
Second, even if section 5902(b.1)(3) were to constitute
the specific offense in this case, it does not provide a mistake-
of-age defense. Though Pennsylvania law does provide a
mistake-of-age defense, it is limited to sexual offenses listed in
Chapter 31 of Pennsylvania’s consolidated statutes. See § 3102
(clarifying situations where the defense is available “in this
chapter” for criminal conduct). Section 5902(b.1)(3), which is
listed under Chapter 59, neither requires knowledge of age as
an element of a prostitution offense nor provides a mistake-of-
age defense.7
We join our sister circuits and hold that mistake of age
is not a defense to § 2423(a) and that the Government is not
required to prove knowledge of the victim’s age. Thus, the
District Court did not err in concluding that mistake-of-age
831 F.3d 431, 434 (7th Cir. 2016). However, unlike Tyson, the
defendant in Ray was indicted for a state offense under §
2423(a)’s catch-all category. See id. (“The indictment charged
Ray with aggravated criminal sexual abuse, in violation of 720
ILCS 5/11-1.60 . . . .”).
7
Tyson acknowledged that Pennsylvania law does not
recognize a mistake-of-age defense to the crime of prostitution.
Oral Arg. at 10:48.
12
evidence is irrelevant to a prosecution pursuant to § 2423(a)
and would likely mislead the jury.
B.
In addition to the § 2423(a) count, the grand jury
indicted Tyson for knowingly using a minor to produce child
pornography in violation of § 2251(a). The statute states:
Any person who employs, uses, persuades,
induces, entices, or coerces any minor to engage
in . . . or who transports any minor in or affecting
interstate or foreign commerce . . . with the intent
that such minor engage in, any sexually explicit
conduct for the purpose of producing any visual
depiction of such conduct or for the purpose of
transmitting a live visual depiction of such
conduct, shall be punished as provided under
subsection (e), if such person knows or has
reason to know that such visual depiction will be
transported or transmitted using any means or
facility of interstate or foreign commerce or in or
affecting interstate or foreign commerce or
mailed . . . or if such visual depiction has actually
been transported or transmitted using any means
or facility of interstate or foreign commerce or in
or affecting interstate or foreign commerce or
mailed.
§ 2251(a). In granting the Government’s motion in limine, the
District Court concluded that “any evidence of mistake of age
. . . is irrelevant” and would likely “confuse or mislead the
jury” because the Government does not need to prove
13
knowledge of age under § 2251(a). App. 12–14. Tyson raises
two arguments as to § 2251(a). First, he points to a perceived
circuit split and lack of controlling authority on whether the
Government must prove knowledge of age. Second, even if
knowledge of age is not an element, Tyson argues that the First
Amendment requires an affirmative mistake-of-age defense.
Tyson claims that neither the Supreme Court nor this
Court have definitely ruled on whether the Government must
prove knowledge of age. In United States v. X-Citement Video,
the Supreme Court analyzed § 2251(a) to clarify the meaning
of 18 U.S.C. § 2252. The majority stated that child
pornography “producers may be convicted under § 2251(a)
without proof they had knowledge of age.” 513 U.S. 64, 76 n.5
(1994); see also Cochran, 17 F.3d at 60–61 (concluding that §
2252 requires knowledge of age after contrasting it with §
2251(a)). While Tyson is correct that these cases consider §
2251(a) in dicta, we nonetheless view them as persuasive
authority. See In re McDonald, 205 F.3d 606, 612 (3d Cir.
2000) (“[W]e should not idly ignore considered statements the
Supreme Court makes in dicta. The Supreme Court uses dicta
to help control and influence the many issues it cannot decide
because of its limited docket.”).
To limit the persuasiveness of the § 2251(a) discussion
in these cases, Tyson points to a supposed circuit split on the
issue.8 Our sister circuits, however, have unequivocally held
8
Tyson cites to decisions from the First and Ninth
Circuits to support his argument that there exists a circuit split.
See United States v. Encarnación-Ruiz, 787 F.3d 581 (1st Cir.
2015); United States v. U.S. District Court (Kantor), 858 F.2d
534 (9th Cir. 1988). We are unpersuaded. While Encarnación-
14
that knowledge of age is not an element of § 2251(a).9 “In the
wake of the X-Citement Video decision, all of the federal courts
of appeals that have considered the issue of scienter under §
2251(a) have held that a defendant’s knowledge of the minor’s
age is not an element of the offense.” Humphrey, 608 F.3d at
960. We see no reason to depart from this consensus. Because
of § 2251(a)’s unambiguous text and history, we join our sister
circuits and hold that the Government is not required to prove
knowledge of age.
The statute’s text and history indicate that Congress did
not intend to require the Government to prove knowledge of
age or provide defendants with an affirmative mistake-of-age
defense. Malloy, 568 F.3d at 171–72. Indeed, Congress
specifically removed “knowingly” from § 2251(a)’s age
element to facilitate enforcement of laws prohibiting the
production of child pornography. See Cochran, 17 F.3d at 60–
61 (discussing Congress’s decision to delete “knowingly” from
Ruiz is limited to an “aider and abettor’s knowledge that the
victim was a minor,” 787 F.3d at 584, Tyson was solely
charged as a principal. Furthermore, Kantor explicitly states
that knowledge is not an element of the statute. 858 F.2d at 538
(“The defendant’s awareness of the subject’s minority is not an
element of the offense.”).
9
See, e.g., United States v. Fletcher, 634 F.3d 395 (7th
Cir. 2011); United States v. Humphrey, 608 F.3d 955 (6th Cir.
2010); United States v. Pliego, 578 F.3d 938 (8th Cir. 2009);
United States v. Malloy, 568 F.3d 166 (4th Cir. 2009); United
States v. Deverso, 518 F.3d 1250 (11th Cir. 2008); United
States v. Griffith, 284 F.3d 338 (2d Cir. 2002); United States v.
Crow, 164 F.3d 229 (5th Cir. 1999).
15
a draft bill due to the Department of Justice’s concern that it
would increase the difficulty of prosecuting child pornography
producers).
Criminal statutes aimed at protecting children from
sexual offenses have long been considered exempt from the
general scienter presumption. See Morissette v. United States,
342 U.S. 246, 251 n.8 (1952) (“Exceptions [to the common law
presumption] came to include sex offenses, such as rape, in
which the victim’s actual age was determinative despite
defendant’s reasonable belief that the girl had reached age of
consent.”). Courts are particularly reluctant to impose a mens
rea requirement to a minor’s age because the Government is
“entitled to greater leeway in the regulation of pornographic
depictions of children.” See New York v. Ferber, 458 U.S. 747,
756 (1982).
Perhaps recognizing the lack of a textual or historical
basis for a mistake-of-age defense, Tyson invites us to read an
affirmative defense into the statute. He cites a Ninth Circuit
decision holding that the First Amendment requires a mistake-
of-age defense to a prosecution under § 2251(a). Appellant’s
Br. 16–18 (citing Kantor, 858 F.2d at 540). In that case, the
Ninth Circuit reasoned that the “imposition of criminal
sanctions on the basis of strict liability . . . would seriously chill
protected speech.” Kantor, 858 F.2d at 540. Rather than
invalidating the statute, the majority instead recognized an
affirmative mistake-of-age defense. Id. at 542. We decline
Tyson’s invitation to join the Ninth Circuit in recognizing an
affirmative defense under the First Amendment. See
Humphrey, 608 F.3d at 960 (noting that “the Ninth Circuit
16
stands alone in its determination that the First Amendment
requires a reasonable mistake-of-age defense”).10
We are unconvinced that excluding mistake-of-age
evidence poses a substantial risk to protected expression.
Perpetrators are well positioned to know the age of a victim
because they “confront[] the underage victim personally.” X-
Citement Video, 513 U.S. at 72 n.2. As for legitimate
producers, only a small subset of pornography—that which
involves “youthful-looking” performers—can conceivably be
subject to criminal prosecution under § 2251(a). Malloy, 568
F.3d at 175–76. Most prosecutions involving this subset
include performers that are undoubtedly children rather than
adults that appear to be young. Id. at 176. In fact, producers are
already required to verify the ages of performers. See 18 U.S.C.
§ 2257(b)(1) (requiring producers to “ascertain . . . the
performer’s name and date of birth”).
Even if interpreting § 2251(a) to preclude mistake-of-
age evidence chills some protected speech, the risk is
significantly outweighed by the Government’s compelling
interest in protecting children from child pornography.
“[S]afeguarding the physical and psychological well-being” of
children is a compelling government interest. Globe
Newspaper Co. v. Superior Court, 457 U.S. 596, 607 (1982).
10
Regardless, Kantor is of limited applicability to the
issue at hand in this case. Kantor involved the production of a
non-obscene film and was decided six years prior to the
Supreme Court’s X-Citement Video decision. Kantor, 858 F.2d
at 538 (“[N]o one claims that [the film] is obscene; the film
would therefore enjoy the protection of the [F]irst
[A]mendment were it not for its depiction of a minor.”).
17
Here, Tyson recorded a video of the underage victim
performing oral sex on him. Section § 2251(a) was enacted
precisely to protect children from the conduct Tyson engaged
in. After all, “[a] democratic society rests, for its continuance,
upon the healthy, well-rounded growth of young people into
full maturity as citizens.” Prince v. Massachusetts, 321 U.S.
158, 168 (1944).
We hold that mistake of age is not a defense to § 2251(a)
because knowledge is not an element of the offense. The statute
also does not contain an affirmative mistake-of-age defense,
and such a defense is not mandated by the Constitution.
Therefore, the District Court did not err in excluding mistake-
of-age evidence.
IV.
Accordingly, for the reasons stated above, we will
affirm the District Court’s grant of the Government’s motion
in limine precluding mistake-of-age evidence.
18