                             PUBLISHED

UNITED STATES COURT OF APPEALS
                 FOR THE FOURTH CIRCUIT


UNITED STATES OF AMERICA,              
                 Plaintiff-Appellee,
                  v.
                                                   No. 05-5243
CHARLES E. JONES, III, a/k/a
Chuckie,
              Defendant-Appellant.
                                       
            Appeal from the United States District Court
      for the Northern District of West Virginia, at Wheeling.
               Frederick P. Stamp, Jr., District Judge.
                             (CR-05-24)

                        Argued: October 26, 2006

                       Decided: December 22, 2006

       Before WILKINSON, NIEMEYER, and WILLIAMS,
                      Circuit Judges.



Affirmed by published opinion. Judge Wilkinson wrote the opinion,
in which Judge Niemeyer and Judge Williams joined.


                              COUNSEL

ARGUED: William Raymond Metzner, Sr., Wheeling, West Vir-
ginia, for Appellant. David J. Perri, Assistant United States Attorney,
OFFICE OF THE UNITED STATES ATTORNEY, Wheeling, West
Virginia, for Appellee. ON BRIEF: Rita R. Valdrini, Acting United
States Attorney, Wheeling, West Virginia, for Appellee.
2                       UNITED STATES v. JONES
                              OPINION

WILKINSON, Circuit Judge:

   This case arises from a prosecution under 18 U.S.C. § 2423(a)
(2000 & Supp. 2003), prohibiting the transportation of a minor across
state lines with the intent that the minor engage in prostitution. Defen-
dant Charles Jones was convicted for his participation in a scheme in
which a thirteen-year-old girl was transported from Ohio to West Vir-
ginia to act as a prostitute at a truck stop. On appeal, Jones contends
that conviction under § 2423(a) requires the government to prove that
he knew the victim was underage. He also argues that remarks made
by the prosecuting attorney during closing argument were improper
and substantially prejudiced his right to a fair trial. Neither argument
has merit. Defendant’s interpretation of § 2423(a) contravenes basic
tenets of statutory construction and subverts Congress’ intent to pro-
tect minors against sexual exploitation. In addition, the challenged
remarks by the prosecuting attorney were not improper. We thus
affirm the judgment of the district court.

                                   I.

   Defendant Charles E. Jones III was indicted by a federal grand jury
in the United States District Court for the Northern District of West
Virginia for one count of Conspiracy to Transport a Minor Across
State Lines for Sexual Purposes (18 U.S.C. §§ 371, 2423(a)) and three
counts of Aiding and Abetting Transportation of a Minor Across State
Lines for Sexual Purposes (18 U.S.C. §§ 2, 2423(a)). The government
alleged that Jones and an associate, Jamie Derek Bennett, transported
a thirteen-year-old girl from Ohio to West Virginia and prostituted her
at a truck stop as a means of funding the purchase of alcohol and ille-
gal drugs.

   In September of 2003, Jones and Bennett met a thirteen-year-old
runaway from Wheeling, West Virginia, in Bellaire, Ohio. For three
consecutive nights beginning on or around September 15, 2003, Jones
and Bennett transported the victim to the Dallas Pike Truck Stop in
West Virginia in order for her to perform sex acts on truckers for
money. Bennett and Jones provided the victim with makeup, skimpy
clothes belonging to Bennett’s ex-girlfriend, and condoms and
                        UNITED STATES v. JONES                        3
douches purchased with money provided by Jones. They developed
a pricing scale for her to use for various sex acts. Jones provided her
with a fake ID.

   On each night at the Truck Stop, the defendant and Bennett waited
in Bennett’s car while the victim went out and displayed herself for
the patrons of the Truck Stop. She performed sex acts inside truck
cabs and, on one occasion, in a room in a nearby motel. Each night,
the victim periodically returned to the car and gave the money she had
earned to defendant Jones; often, Jones and Bennett would encourage
her to go make more. The victim made hundreds of dollars, most of
which was taken from her by Jones and Bennett. At the end of the
night, the three would return to Bellaire and purchase alcohol and
drugs with the prostitution proceeds. On the third night, the victim
had a dangerous encounter with a "customer" and twisted her ankle
in flight. At that point, she decided that she did not want to engage
in any more prostitution.

   At trial, the victim and Bennett testified that both Bennett and
defendant Jones were present for all three trips to the Truck Stop. A
companion named Jeffrey Joe Hall testified to having been present for
two trips. The defendant’s cousin, Charles Patterson, testified that on
the first trip Jones stopped at his house to ask directions to the Truck
Stop. Several witnesses testified that they saw the victim in the pres-
ence of Jones in Bellaire and heard him offer her sexual services to
associates there. At the time and months afterward, Jones bragged to
witnesses about "pimping out" the victim at Dallas Pike Truck Stop.

   On Sunday, September 21, 2003, Bellaire police officers found the
victim. The police spoke to Jones, who made a written statement that
he, Bennett, and the victim had driven to Dallas Pike in order for the
victim to visit someone, but he mentioned nothing about prostitution.
Bennett was the first participant to disclose the prostitution scheme,
and he eventually pled guilty to conspiracy and testified at trial. Hall
also admitted his involvement, pled guilty to Lying to a Federal
Agent, and testified at trial. Patterson had no involvement in the pros-
titution scheme and testified at trial.

   At the close of a three-day jury trial on September 15, 2005, the
jury convicted Jones on all counts. On December 5, 2005, the district
4                           UNITED STATES v. JONES
court conducted a sentencing hearing at which it sentenced the defen-
dant to 63 months of imprisonment.

   On appeal, defendant argues that the district court erred in deter-
mining that 18 U.S.C. § 2423(a) does not require proof that the defen-
dant knew that the victim was under eighteen years of age. He also
argues that during closing argument, the prosecutor made improper
comments which prejudicially affected his right to a fair trial.

                                       II.

   Jones first argues that 18 U.S.C. § 2423(a) requires the government
to prove that the defendant knew that the alleged victim was under
eighteen years of age. At the time of defendant Jones’ alleged offense,1
§ 2423(a) provided:

        A person who knowingly transports an individual who has
        not attained the age of 18 years in interstate or foreign com-
        merce, or in any commonwealth, territory or possession of
        the United States, 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 5 years and not more
        than 30 years.

18 U.S.C. § 2423(a). The defendant contends that "knowingly"
applies to the clause "who has not attained the age of 18 years" and
thus that the defendant’s knowledge of the victim’s minority is an ele-
ment of the offense which the government must prove to convict. We
disagree. In doing so, we join the four other circuits to have consid-
ered this question, all of which have stated that the victim’s minor sta-
    1
     18 U.S.C. § 2423(a) has since been amended to provide:
        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 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.
                        UNITED STATES v. JONES                         5
tus is instead a fact which the prosecution must prove and for which
the defendant is responsible. See United States v. Griffith, 284 F.3d
338, 351 (2d Cir. 2002); United States v. Taylor, 239 F.3d 994, 997
(9th Cir. 2001); United States v. Scisum, 32 F.3d 1479, 1485-86 (10th
Cir. 1994); United States v. Hamilton, 456 F.2d 171, 173 (3d Cir.
1972) (per curiam). In the time since other circuit courts have inter-
preted § 2423(a) as we do today, Congress has amended § 2423 no
less than nine times, never changing it to require the government to
establish the defendant’s knowledge of the alleged victim’s age. See
Pub. L. No. 109-248, 120 Stat. 613 (2006); Pub. L. No. 108-21, 117
Stat. 652 (2003); Pub. L. No. 107-273, 116 Stat. 1808 (2002); Pub.
L. No. 105-314, 112 Stat. 2976 (1998); Pub. L. No. 104-294, 110
Stat. 3499 (1996); Pub. L. No. 104-71, 109 Stat. 774 (1995); Pub. L.
No. 103-322, 108 Stat. 2037 (1994); Pub. L. No. 99-628, 100 Stat.
3510 (1986); Pub. L. No. 95-225, 92 Stat. 7 (1978).

                                   A.

    The Supreme Court has "long recognized that determining the
mental state required for commission of a federal crime requires ‘con-
struction of the statute and . . . inference of the intent of Congress.’"
Staples v. United States, 511 U.S. 600, 605 (1994) (citation omitted).
In this case, construction of the statute demonstrates that it does not
require proof of the defendant’s knowledge of the victim’s minority.
It is clear from the grammatical structure of § 2423(a) that the adverb
"knowingly" modifies the verb "transports." Adverbs generally mod-
ify verbs, and the thought that they would typically modify the infi-
nite hereafters of statutory sentences would cause grammarians to
recoil. We see nothing on the face of this statute to suggest that the
modifying force of "knowingly" extends beyond the verb to other
components of the offense. "A more natural reading of the statute . . .
is that the requirement of knowledge applies to the defendant’s con-
duct of transporting the person rather than to the age of the person
transported." Taylor, 239 F.3d at 997.

   Our interpretation gains further support from a related provision of
the same statute, 18 U.S.C. § 2421 (2000). While § 2423 is entitled
"Transportation of minors," § 2421 is entitled "Transportation gener-
ally" and provides:
6                       UNITED STATES v. JONES
    Whoever knowingly transports any individual in interstate
    or foreign commerce, or in any Territory or Possession of
    the United States, with intent that such individual engage in
    prostitution, or in any sexual activity for which any person
    can be charged with a criminal offense, or attempts to do so,
    shall be fined under this title or imprisoned not more than
    10 years, or both.

18 U.S.C. § 2421. Section 2421 is virtually identical to § 2423(a) but
for its lack of an age element. In the context of § 2421, the adverb
"knowingly" obviously modifies the verb, "transports." It would be
implausible to suggest that "knowingly" in § 2421 is intended to mod-
ify the noun "individual." So, too, would it be implausible to suggest
that, in § 2423(a), where the noun "individual" is modified by the
clause "who has not attained the age of 18 years," the term "know-
ingly" suddenly applies to both the noun and its dependent clause.
Not only is such a reading grammatically odd, but it would have the
perverse effect of making it much more difficult to prove a violation
of § 2423(a) than of § 2421. It is unlikely that, in providing extra pro-
tection for minors in § 2423(a), Congress intended to make the evi-
dentiary burdens of that provision disproportionate to those of § 2421.
The more natural reading of § 2421 and § 2423(a) is that the adverb
"knowingly" serves the same function in each: to modify the verb
"transports."

   Our holding today is also consistent with a large body of circuit
precedent recognizing that a statutory mens rea requirement does not
always apply to each factual element of a criminal offense. With
regard to a similar statute, this court has held that conviction under
21 U.S.C. § 861(a)(3) for receiving a controlled substance from a per-
son under 18 years of age does not require proof that the defendant
knew the other party was underage. United States v. Cook, 76 F.3d
596, 602 (4th Cir. 1996). Similarly, this court has held that to estab-
lish a knowing violation of 18 U.S.C. § 922(g), which criminalizes
possession of firearms by prohibited persons, the United States must
prove the defendant’s knowledge with respect to possession of the
firearm but not with respect to other elements of the offense. See 18
U.S.C. §§ 922(g), 924(a)(2)(2000). See, e.g., United States v. Frazier-
El, 204 F.3d 553, 561 (4th Cir. 2000) (government need not prove
that defendant knew possession of particular type of firearm was pro-
                        UNITED STATES v. JONES                         7
hibited); United States v. Mitchell, 209 F.3d 319, 322 (4th Cir. 2000)
(government need not establish that defendant knew possessing a fire-
arm was illegal); United States v. Bostic, 168 F.3d 718, 722-23 (4th
Cir. 1999) (same); United States v. Langley, 62 F.3d 602, 606 (4th
Cir. 1995) (en banc) (government need not prove defendant’s knowl-
edge of his felony status or firearm’s interstate nexus).

   Finally, our interpretation is the only one consistent with any rea-
sonable "inference of the intent of Congress." Staples, 511 U.S. at 605
(internal quotation marks omitted). Under § 2423(a), "the fact that the
individual being transported is a minor creates a more serious crime
in order to provide heightened protection against sexual exploitation
of minors." Taylor, 239 F.3d at 997 (citing H.R. Rep. No. 105-557
(1998)(justifying increased penalties under § 2423(a)). It is reason-
able to conclude that "the age of the victim simply subjects the defen-
dant to a more severe penalty in light of Congress’ concern about the
sexual exploitation of minors." Id. See also Hamilton, 456 F.2d at
173.

   The defendant’s interpretation, meanwhile, would strip the statute
of its clear purpose: the protection of minors. If the prosecution were
required to prove knowledge with regard to the victim’s age, it would
be the rare defendant who would not claim to have mistaken the vic-
tim for an adult. Imposing such a mens rea requirement would be tan-
tamount to permitting adults to prey upon minors so long as they
cultivate ignorance of their victims’ age. But "the statute is intended
to protect young persons who are transported for illicit purposes, and
not transporters who remain ignorant of the age of those whom they
transport." Taylor, 239 F.3d at 996. It would be nonsensical to require
proof of knowledge of the victim’s age when the statute exists to pro-
vide special protection for all minors, including, if not especially,
those who could too easily be mistaken for adults. Such minors are
still minors, "regardless of what [they] say[ ] or how [they] appear[ ]."
Id. at 997. For this reason, "[i]gnorance of the victim’s age provides
no safe harbor from the penalties in 18 U.S.C. § 2423(a)." Id.

                                   B.

  The defendant argues that § 2423(a) should be construed by anal-
ogy to the federal child pornography statutes, 18 U.S.C. § 2252(a) and
8                       UNITED STATES v. JONES
18 U.S.C. § 2252(A). In United States v. X-Citement Video, Inc., 513
U.S. 64, 78 (1994), the Supreme Court held that the term "knowingly"
in § 2252 extends to the minority status of the individuals depicted.
The Court stated that this was not "[t]he most natural grammatical
reading" of the statute, id. at 68, but nevertheless "the presumption in
favor of a scienter requirement should apply to each of the statutory
elements that criminalize otherwise innocent conduct," id. at 72. In
the case of non-obscene pornographic material, "one would reason-
ably expect to be free from regulation when trafficking in sexually
explicit, though not obscene, materials involving adults. Therefore,
the age of the performers is the crucial element separating legal inno-
cence from wrongful conduct." Id. at 73. Because the minority status
of the depicted individuals is what separates criminal child pornogra-
phy from lawful material, knowledge that the pornography depicts
minors is properly an element to be required for a defendant’s convic-
tion. Id. at 72-73. See also United States v. Cedelle, 89 F.3d 181, 185
(4th Cir. 1996).

   Similarly, in Staples v. United States, 511 U.S. 600 (1994), the
Supreme Court addressed the proper construction of 26 U.S.C.
§ 5861(d), which criminalizes possession of an unregistered "fire-
arm," where the term "firearm" is defined to include automatic but not
all semiautomatic weapons. 26 U.S.C. §§ 5845(a), (b). The Court held
that, where a defendant is arrested for possession of a semiautomatic
rifle modified for fully automatic fire, the prosecution must establish
that defendant knew the gun was capable of firing automatically. The
Court reasoned that "if Congress had intended to make outlaws of gun
owners who were wholly ignorant of the offending characteristics of
their weapons, and to subject them to lengthy prison terms, it would
have spoken more clearly to that effect." 511 U.S. at 620; see id. at
611-12.

   In this case, the reasoning of X-Citement Video and Staples is inap-
posite. "The Supreme Court’s holding in Staples, as well as in the
related case of [X-Citement Video] was directed at awareness of the
elements that define circumstances upon which criminality turns."
Bostic, 168 F.3d at 723. But in § 2423(a), the minority of the victim
is hardly a factor that distinguishes the defendant’s actions from "in-
nocent conduct." X-Citement Video, 513 U.S. at 72. To the contrary,
"the transportation of any individual for purposes of prostitution or
                        UNITED STATES v. JONES                          9
other criminal sexual activity is already unlawful under federal law."
Taylor, 239 F.3d at 997 (citing 18 U.S.C. § 2421) (emphasis added).
See, e.g., Cook, 76 F.3d at 601 ("[T]here is no reason to apply the pre-
sumption in favor of a knowledge requirement [to 21 U.S.C.
§ 861(a)(3)] to protect otherwise innocent conduct for the obvious
reason that receiving illegal drugs is not otherwise innocent con-
duct."); United States v. LaPorta, 46 F.3d 152, 158 (2d Cir. 1994)
("Arson is hardly ‘otherwise innocent conduct.’") (construing 18
U.S.C. § 1361). Because an individual "is already on notice that he is
committing a crime when he transports an individual of any age in
interstate commerce for the purpose of prostitution," Griffith, 284
F.3d at 351, it is both reasonable and just to conclude that "the trans-
porter assumes the risk that the victim is a minor." Taylor, 239 F.3d
at 997.

   For these reasons, under § 2423(a) the government is not required
to establish the defendant’s knowledge of the alleged victim’s age.
The district court thus did not err in either its ruling on the govern-
ment’s motion in limine or its instructions to the jury.

                                   III.

   Jones also contends that, in closing argument, the prosecuting
attorney made two improper comments which were prejudicial to the
outcome of the case. Comments by a prosecutor can constitute
grounds for reversal where the comments were improper and where
they so prejudicially affected the defendant’s substantial rights as to
deprive him of a fair trial. See United States v. Ollivierre, 378 F.3d
412, 420 (4th Cir. 2004), sentence vacated under Booker, 543 U.S.
1112 (2005); United States v. Curry, 993 F.2d 43, 45 (4th Cir. 1993);
United States v. Chorman, 910 F.2d 102, 113 (4th Cir. 1990).2
  2
   If a court finds the prosecution’s remarks to be improper, their preju-
dicial effect is assessed through a consideration of a number of factors,
including (1) the degree to which the remarks tended to mislead the jury
or prejudice the accused; (2) whether the remarks were isolated or exten-
sive; (3) the strength of the evidence supporting guilt in the absence of
the remarks; (4) whether the comments were deliberately placed in front
of the jury to divert attention to extraneous matters; (5) whether the
remarks were invited by improper conduct of defense counsel; and (6)
10                      UNITED STATES v. JONES
                                   A.

   In the first challenged comment, the prosecuting attorney during
closing argument asked the jury, "Ladies and gentlemen, if [the
defense] had real evidence, don’t you think they would have pre-
sented it to you?" The defendant alleges that this remark was an
improper comment upon the defendant’s failure to testify on his own
behalf.

   "The Fifth Amendment precludes a prosecutor from commenting to
a jury on the failure of an accused to testify in his own defense." Olli-
vierre, 378 F.3d at 419. In considering whether a prosecutor’s words
constitute a comment on the defendant’s failure to testify, this court
asks, "Was the language used manifestly intended to be, or was it of
such character that the jury would naturally and necessarily take it to
be a comment on the failure of the accused to testify?" United States
v. Francis, 82 F.3d 77, 78 (4th Cir. 1996) (quoting United States v.
Anderson, 481 F.2d 685, 701 (4th Cir. 1973)). To answer these ques-
tions, the court evaluates the comment "in the context in which it was
made." United States v. Percy, 765 F.2d 1199, 1204 (4th Cir. 1985).

   The government contends that the prosecuting attorney’s remark
referred to an alternative factual scenario presented by defense coun-
sel in his closing argument. During closing argument, defense counsel
told the jury, "[I]f there is a scenario that you can reasonably believe,
not proven beyond a reasonable doubt, but that it is possible that this
happened, that explains this week without the defendant having com-
mitted a crime, then you are going to have to acquit. And I am going
to suggest a scenario to you. . . ."

   Defense counsel went on to outline a sequence of events wherein
the victim and Jamie Derek Bennett created the prostitution scheme
without the defendant’s knowledge. Defense counsel asserted that the

whether curative instructions were given to the jury. See United States
v. Wilson, 135 F.3d 291, 299 (4th Cir. 1998). While we hold that the
challenged comments were not improper, even if they were somehow
deemed error, they are harmless and would not justify overturning the
jury’s verdict.
                        UNITED STATES v. JONES                        11
defendant went on the first trip to the truck stop unaware of the prosti-
tution scheme and was not present at all for the second and third trips.
Defense counsel suggested that the defendant eventually deduced that
the victim was a runaway minor and decided to have nothing more
to do with her. The girl, meanwhile, when located by the police,
decided to "burn" her former associates because she was angry at
them. Defense counsel concluded his closing argument by stating, "I
submit that when you go into deliberation and if you choose to start
talking and running scenarios and how you do deliberations is your
business, but if you run scenarios, there are numerous situations that
you can — that you can determine that this individual didn’t know
what was going to happen on trip one, was reasonable, didn’t go on
trip two, didn’t go on trip three."

   During the trial, the defense presented seven witnesses, none of
whom offered any testimony substantiating the alternative factual sce-
nario presented by defense counsel in closing argument. Cross-
examination of the prosecution’s witnesses similarly failed to elicit
support for this scenario. The government contends that it was this
failure to substantiate the alternative scenario to which the prosecut-
ing attorney referred in asking, "[I]f they had real evidence, don’t you
think they would have presented it to you?"

   We agree that the remark, in context, was not intended to comment
on the defendant’s failure to testify, nor would the jury naturally and
necessarily take it as such. See Francis, 82 F.3d at 78. A comment on
the weaknesses of the defense’s case is not necessarily, or even ordi-
narily, a comment upon the defendant’s failure to testify. See Percy,
765 F.2d at 1204-05 (statement that prosecution’s case remained "un-
refuted and unrebutted" was not a comment on failure to testify);
Anderson, 481 F.2d at 701 (question "What do the defendants say?"
not a comment on failure to testify). See also United States v. Glantz,
810 F.2d 316, 321-22 (1st Cir. 1987) (comments on lack of evidence
were permissibly directed at weakness of defense’s theory). To view
such general comments on the inadequacies of an opponent’s case as
improper is to strike at the heart of the adversary system. Adversaries
are supposed to expose the weakness of each other’s evidence, and
the prosecution committed no error in doing just that.
12                      UNITED STATES v. JONES
                                   B.

   Also during closing argument, the prosecuting attorney stated to
the jury, "[Y]ou can be confident that [witness Jamie Derek Bennett]
is telling the truth about this conspiracy. You know why? Because he
pled to it." Defense counsel asked to approach the bench and argued
that the statement was improper. The judge agreed and immediately
told the jury to disregard the last statement by the prosecutor. The
defendant contends that the prosecuting attorney’s statement consti-
tuted improper vouching which so prejudicially affected the defen-
dant’s substantial rights as to deprive him of a fair trial.

   "Vouching occurs when the prosecutor indicates a personal belief
in the credibility or honesty of a witness." United States v. Sullivan,
455 F.3d 248, 259 (4th Cir. 2006) (quoting United States v. Sanchez,
118 F.3d 192, 198 (4th Cir. 1997)).3 "[P]resenting evidence on a wit-
ness’ obligation to testify truthfully pursuant to an agreement with the
government and arguing that this gives the witness a strong motiva-
tion to tell the truth is not, by itself, improper vouching." United
States v. Collins, 415 F.3d 304, 308 (4th Cir. 2005) (quoting United
States v. Bowie, 892 F.2d 1494, 1498 (10th Cir. 1990)). Reference to
a plea agreement "becomes impermissible vouching only when the
prosecutors explicitly or implicitly indicate that they can monitor and
accurately verify the truthfulness of the witness’ testimony." Id.
(quoting Bowie, 892 F.2d at 1498).

   In this case, the prosecuting attorney’s comment did not convey,
either implicitly or explicitly, an expression of the prosecutor’s or the
government’s opinion as to the witness’s veracity. See Sanchez, 118
F.3d at 198 (prosecutor’s comment not an expression of opinion);
Ollivierre, 378 F.3d at 423 (same). Rather, the remark in this case is
  3
   While vouching constitutes an expression of belief or opinion regard-
ing the credibility or honesty of a witness, "bolstering is an implication
by the government that the testimony of a witness is corroborated by evi-
dence known to the government but not known to the jury." Sanchez, 118
F.3d at 198. The defendant did not allege that the prosecuting attorney’s
comment constituted improper bolstering, only vouching. In any case,
the prosecutor’s remark in no way referenced evidence known to the
government and unknown to the jury.
                        UNITED STATES v. JONES                       13
similar to that at issue in United States v. Sullivan, where this court
found that the government did not improperly vouch for its witness
by referring to a plea agreement and stating, "It should be clear that
the witness has far more of an incentive to tell the truth than to lie."
455 F.3d at 259. Here, as in Sullivan, "the AUSA made no statement
about [his] personal belief in the truth of the statement, only that,
given the circumstances of a plea agreement . . . it is more in the sub-
ject’s interest to be honest than to be dishonest." Id. Such a statement
is not impermissible vouching but a permissible reference to facts rel-
evant to the jury’s assessment of the witness’s credibility.

                                  IV.

   Congress enacted § 2423(a) to punish those who offer up young
lives to prostitution and who are heedless of the scars they leave and
the human devastation that they cause. That statutory intent has been
faithfully followed in this case. The judgment of the district court is
affirmed.

                                                           AFFIRMED
