FOR PUBLICATION
 UNITED STATES COURT OF APPEALS
      FOR THE NINTH CIRCUIT

UNITED STATES OF AMERICA,                  No. 07-10174
                Plaintiff-Appellee,
               v.                            D.C. No.
                                          CR-05-01145-SMM
CRISTINO LOPEZ-MARTINEZ,
                                              OPINION
             Defendant-Appellant.
                                      
       Appeal from the United States District Court
                for the District of Arizona
      Stephen M. McNamee, District Judge, Presiding

                  Argued and Submitted
         June 12, 2008—San Francisco, California

                 Filed September 10, 2008

 Before: A. Wallace Tashima, M. Margaret McKeown, and
            Ronald M. Gould, Circuit Judges.

               Opinion by Judge McKeown




                           12671
             UNITED STATES v. LOPEZ-MARTINEZ       12675


                      COUNSEL

Michael Shay Ryan, Kent & Ryan, P.L.C., Phoenix, Arizona,
for the defendant-appellant.
12676          UNITED STATES v. LOPEZ-MARTINEZ
Tracey A. Bardorf, Assistant United States Attorney, Phoenix,
Arizona, for the plaintiff-appellee.


                          OPINION

McKEOWN, Circuit Judge:

   After a five-day trial, a jury convicted Cristino Lopez-
Martinez of one count of conspiracy to bring aliens to the
United States, in violation of 8 U.S.C. § 1324(a)(1)(A)(v)(I);
one count of aiding and abetting bringing aliens to the United
States resulting in death, in violation of 8 U.S.C.
§ 1324(a)(1)(B)(iv); three counts of aiding and abetting bring-
ing aliens to the United States for profit, in violation of 8
U.S.C. § 1324(a)(2)(B)(ii); and one count of illegal re-entry
after deportation, in violation of 8 U.S.C. § 1326(a). Lopez-
Martinez now appeals his conviction (except the illegal re-
entry count) on a multitude of grounds, attacking the actions
of the judge, the prosecutor, and the jury. We affirm.

I.   FACTUAL AND PROCEDURAL BACKGROUND

  Lopez-Martinez was convicted based largely on the testi-
mony of Eduardo Camacho-Reyes. The following account of
events is taken from that testimony. In the summer of 2005,
Camacho-Reyes hired Miguel Cruz-Morales to bring him, his
wife, and his two young daughters from Mexico to the United
States through the Arizona desert. For this service, Camacho-
Reyes agreed to pay $1,800.

  In late September, the Camacho-Reyes family traveled to
Northern Mexico, where they were met by Miguel and his
brother, Cecilio Cruz-Morales, who took them to a house to
await the rest of the group that would travel with them. Two
evenings later, after the rest of the group arrived, they took a
bus into the desert and then began walking. It was at this point
               UNITED STATES v. LOPEZ-MARTINEZ           12677
that Camacho-Reyes first saw the man known as “Pedro,”
whom he later identified as Cristino Lopez-Martinez, the
defendant.

   As they walked, Lopez-Martinez and each of the Cruz-
Morales brothers alternated walking at the front of the group,
with one of the others in the middle of the group, and the
other one at the back. During breaks, the three men gathered
away from the rest of the group and spoke in an indigenous
dialect.

   The group walked for two nights and two days. Around the
middle of the second day, Araceli Escobar-Villa, Camacho-
Reyes’ wife, collapsed. When Lopez-Martinez came back to
check on the family, Camacho-Reyes, who had seen him ear-
lier with a cell phone, asked Lopez-Martinez to call the immi-
gration authorities. Lopez-Martinez replied that he would do
so, but only after he moved the rest of the group further ahead
“so that he didn’t lose them all.” Lopez-Martinez returned to
the Camacho-Reyes group twice more. After returning for the
second time, and learning that Escobar-Villa was dead,
Lopez-Martinez left and never returned. About twenty min-
utes after Lopez-Martinez left, the border patrol indepen-
dently discovered the group, provided them medical care, and
then began processing them for removal to Mexico.

   Lopez-Martinez and Miguel Cruz-Morales were found by
the border patrol early the next morning, hiding under a bush
behind an Exxon station in nearby Dateland, Arizona. When
the border patrol agent asked the pair whether they had left
anyone out in the desert, Lopez-Martinez replied, “No.”
Eventually, the border patrol discovered that Lopez-Martinez
and Cruz-Morales were part of the group rescued earlier that
day. Camacho-Reyes picked Lopez-Martinez and the Cruz-
Morales brothers out of a lineup as the leaders of the group.
Lopez-Martinez was arrested, tried, and convicted.
12678             UNITED STATES v. LOPEZ-MARTINEZ
II.    ANALYSIS

  A.    THE TRIAL

   Lopez-Martinez was tried before a jury. The trial judge
played an active role in the trial. During a break in the prose-
cution’s direct examination of Camacho-Reyes, after the jury
had been excused, the judge asked counsel to remain. The
judge then explained that he had “some concerns about the
quantum of evidence.” To the prosecutor, the judge directed:

      [Y]ou have to get the underlying facts out . . . .
      [T]here’s no indication as to when [Lopez-Martinez]
      was leading what [Camacho-Reyes] observed, what
      he saw [the alleged smugglers] do. And until you can
      get some factual underpinnings there, just to let
      [Camacho-Reyes] say, I think [Lopez-Martinez] was
      a smuggler, there’s no facts by which to help the jury
      out.

The judge and prosecutor went back and forth for a time, with
the prosecutor explaining how she had made, or planned to
make, her case, and the judge explaining where he found
holes in her evidence and what sort of testimony would be
necessary to fill in the gaps. Contrary to Lopez-Martinez’s
view of the exchange, the judge’s remarks were not improper.

   [1] Lopez-Martinez seems to believe that a trial judge’s
only role is to call “balls and strikes,” standing by to observe
and occasionally ruling on objections pitched out by the attor-
neys. This characterization misconceives the role of the trial
judge: “A trial judge is more than an umpire.” United States
v. Laurins, 

, 537 (9th Cir. 1988). And during a
jury trial, the judge is surely more than a robed figurehead
who simply observes the proceedings and keeps order. As we
have explained, a judge “may participate in the examination
of witnesses to clarify evidence, confine counsel to evidenti-
                UNITED STATES v. LOPEZ-MARTINEZ            12679
ary rulings, ensure the orderly presentation of evidence, and
prevent undue repetition.” 

we have not had an opportunity, until now, to
directly address the question, our sister circuits have held that
there is nothing wrong with a judge suggesting a line of ques-
tioning to an attorney. See United States v. Ramos, 

, 746 (1st Cir. 1969) (per curiam) (holding suggestions
“by trial judges to prosecutors concerning elements of proof
and appropriate lines of inquiry have often been held proper,
even when made in the presence of the jury”); Fischer v.
United States, 

, 444-45 (10th Cir. 1954) (noting
the “court has the power, within reasonable bounds, to ques-
tion a witness . . . and there is no reason why it may not direct
an attorney to pursue a line of questioning if it is relevant to
the case”). We agree with the reasoning of these courts; it
would be disingenuous to condemn the trial judge’s inquiry
here, given that it is already well established that the judge
may question the witness directly.

   [3] We are mindful, of course, that in some cases —
although not here — the trial judge’s inquiries and sugges-
tions may cross the line and affect the judge’s role as an
impartial participant in the trial process. “A trial judge’s par-
ticipation [can] overstep[ ] the bounds of propriety and
deprive[ ] the parties of a fair trial . . . when ‘the record dis-
closes actual bias . . . or leaves the reviewing court with an
abiding impression that the judge’s remarks and questioning
of witnesses projected to the jury an appearance of advocacy
or partiality.” United States v. Parker, 

, 1119
(9th Cir. 2001) (quoting United States v. Mostella, 

, 361 (9th Cir. 1986)). The judge’s remarks objected to by
Lopez-Martinez were made outside the presence of the jury,
and evidenced no bias on the part of the judge.

  [4] On the contrary, the record suggests that the trial
judge’s intent was to protect Lopez-Martinez and the fair trial
process. After Lopez-Martinez objected to the judge’s collo-
12680             UNITED STATES v. LOPEZ-MARTINEZ
quy with the prosecutor, and insinuated that the court was
encouraging the prosecution to manufacture testimony, the
judge explained that he was concerned that he could not grant
a Rule 29 motion in Lopez-Martinez’s favor without giving
the prosecution a chance to meet his concerns.1 Additionally,
the judge emphasized that Lopez-Martinez was facing a very
serious sentence, and that he did not want to see Lopez-
Martinez convicted on accusations unsupported by evidence.
The clear import of this record, then, is not bias toward
Lopez-Martinez, but rather the judge’s desire to shore up any
Rule 29 ruling in Lopez-Martinez’s favor against appeal, and
to ensure that if Lopez-Martinez was convicted, it was on the
basis of evidence, not speculation. Given the absence of evi-
dence of actual (or even implied) bias and the lack of any
effect on the jury, there is no basis for Lopez-Martinez’s
claim that the trial judge’s remarks were improper.

   In presenting its case, the prosecution introduced expert
testimony from Border Patrol Agent Hector Martinez. After
recounting his experience and training, Agent Martinez testi-
fied about the methods and patterns of human smugglers in
the Yuma area. On appeal, for the first time, Lopez-Martinez
argues that Agent Martinez should not have been allowed to
testify as an expert.2 We disagree.

  [5] As the Supreme Court emphasized in Kumho Tire Co.,
Ltd. v. Carmichael, 

(1999), with respect to
expert testimony “the test of reliability is ‘flexible’ [and] the
law grants a district court the same broad latitude when it
   1
     Rule 29 provides in part: “After the government closes its evidence or
after the close of all the evidence, the court on the defendant’s motion
must enter a judgment of acquittal of any offense for which the evidence
is insufficient to sustain a conviction.” FED. R. CRIM. P. 29(a).
   2
     Because Lopez-Martinez did not raise this issue below, we review the
admission of this testimony only for plain error, and will “only reverse if
the district court committed a clear or obvious error that affected substan-
tial rights or was prejudicial.” United States v. Sherwood, 

,
408 (9th Cir. 1996).
               UNITED STATES v. LOPEZ-MARTINEZ             12681
decides how to determine reliability as it enjoys in respect to
its ultimate reliability determination.” 

Lopez-
Martinez’s objections boil down to criticism of the trial judge
for not conducting a more formal Daubert hearing, or requir-
ing Agent Martinez to give a precise description of each step
in the logical chain he used to arrive at his conclusions. See
Daubert v. Merrell Dow Pharm., Inc., 

, 589
(1993). But, these procedures are not required under Supreme
Court precedent or our own case law.

   [6] Agent Martinez, who has fourteen years of experience
as a border patrol agent, including five as the intelligence
chief for the Yuma station, testified about patterns and meth-
ods common among smugglers in the Yuma area. This evi-
dence was neither rocket science nor complex statistical
modeling. Agent Martinez’s explanation of his methods and
experience was sufficient for the trial judge to be confident in
their reliability. See FED. R. EVID. 702 (stating expert testi-
mony may be admitted whenever “it will assist the trier of
fact,” and that a witness may be qualified by, inter alia, expe-
rience, training, or education). The court did not plainly err in
admitting this testimony.

   [7] In light of Agent Martinez’s testimony, as well as the
testimony of the other witnesses, neither did the court err in
denying Lopez-Martinez’s Rule 29 motion. When viewed in
the light most favorable to the prosecution, a reasonable jury
could easily have found the evidence sufficient. See United
States v. Moses, 

, 987 (9th Cir. 2007) (“Evidence
is sufficient to support a conviction if viewing the evidence in
the light most favorable to the prosecution, any rational trier
of fact could have found the essential elements of the crime
beyond a reasonable doubt.”) (internal quotations omitted).

   The main fact in dispute at trial was whether the prosecu-
tion had sufficiently demonstrated that Lopez-Martinez was a
foot guide for the group, as opposed to just another client of
the smugglers. That this fact was disputed, however, does not
12682          UNITED STATES v. LOPEZ-MARTINEZ
mean that the jury unreasonably found Lopez-Martinez guilty;
the jury’s job as the factfinder was precisely to resolve dis-
puted issues of fact.

   [8] Camacho-Reyes testified that Lopez-Martinez led the
group during the times when he was in front, and that he
would regularly switch places with the Morales brothers in
what appeared to be a coordinated fashion. During breaks,
Lopez-Martinez and the Morales brothers would gather away
from the rest of the group, and talk among themselves. Lopez-
Martinez had a cell phone with him, which would be very
unusual for a smuggling client, but common for a smuggler.
And, Agent Martinez confirmed that Lopez-Martinez’s
behavior, as described by Camacho-Reyes, fit the patterns that
he had observed among smugglers. Viewing the testimony in
the light most favorable to the prosecution, a reasonable jury
could have found beyond a reasonable doubt that Lopez-
Martinez was one of the guides, not simply a client of the
Morales brothers.

   [9] Lopez-Martinez’s remaining arguments in support of
his Rule 29 motion are based on misapprehensions of the
applicable law. Contrary to Lopez-Martinez’s assertion, a
defendant need not personally know a victim or directly cause
the victim’s death to be convicted of bringing aliens to the
United States resulting in death under 8 U.S.C.
§ 1324(a)(1)(B)(iv). All that is required under this section is
that a defendant know he is bringing aliens to the United
States and that the bringing of those aliens to the United
States “results in the death of any person.” 8 U.S.C.
§ 1324(a)(1)(B)(iv). Any argument by Lopez-Martinez that he
did not know the others in the group were illegal aliens strains
credulity.

   [10] Similarly, Lopez-Martinez’s argument that the govern-
ment failed to establish that he was working for financial gain
fails to appreciate the relevant law; where a defendant is
charged with aiding and abetting the bringing of aliens to the
               UNITED STATES v. LOPEZ-MARTINEZ          12683
United States for financial gain, as Lopez-Martinez was, the
government need only show that the principals stood to bene-
fit financially from the smuggling. See United States v. Tsai,

, 697 (9th Cir. 2002) (“Because Tsai was
charged as an aider and abettor under 18 U.S.C. § 2, the gov-
ernment could make out this element merely by proving that
a principal — not necessarily Tsai himself — committed the
crime with a pecuniary motive; it need not show ‘actual pay-
ment or even an agreement to pay.’ ”) (quoting United States
v. Angwin, 

, 998 (9th Cir. 2001)); see also
United States v. Munoz, 

, 1046-47 (9th Cir.
2005) (reaffirming the holding of Tsai with respect to aiders
and abettors). The Rule 29 motion was properly denied.

  Lopez-Martinez directs his last trial challenge to the fol-
lowing comments made by the prosecutor during her closing
argument:

    When Agent Vasquez encountered [Lopez-Martinez]
    and [Miguel] . . . [Lopez-Martinez] was not worried
    about that group he just left in the desert. And he
    wasn’t showing it. He didn’t try to tell Agent
    Vasquez: I’m with a group of 20, and there’s a
    bunch of my fellow countrymen back in the desert
    with a woman who died. . . . Why didn’t he just say:
    I left to get water. Thank God you are here. Because
    he has a guilty conscience, that’s why . . . he didn’t
    want to get caught for bringing those people in and
    leaving a woman who is dead in the desert.

Lopez-Martinez did not object to this statement at the time,
however, and it was not plain error to allow it. See United
States v. Whitehead, 

(9th Cir. 2000).

  [11] When Agent Vasquez first discovered Lopez-Martinez
and Miguel hiding behind the gas station, after introducing
himself and inquiring if they were okay, he asked where they
were from and whether they had left anyone behind in the
12684          UNITED STATES v. LOPEZ-MARTINEZ
desert. Lopez-Martinez said “no,” no one else was with them.
Lopez-Martinez portrays the prosecutor’s reference to this
exchange as an infringement of his Fifth Amendment right to
remain silent, but this argument overlooks a key point: Lopez-
Martinez did not invoke his Fifth Amendment right to remain
silent; rather, he affirmatively misstated to Agent Vasquez
that no one else was with him and Miguel and that they had
not left the group alone in the desert. To be sure, the Fifth
Amendment protects a person’s right to remain silent in the
face of custodial questioning by the government, but if one
chooses to answer the government’s questions, nothing in the
Fifth Amendment protects those answers. See LaChance v.
Erickson, 

, 265 (1998) (“Our legal system pro-
vides methods for challenging the Government’s right to ask
questions — lying is not one of them. A citizen may decline
to answer the question, or answer it honestly, but he cannot
with impunity knowingly and willfully answer with a false-
hood.”) (quoting Bryson v. United States, 

, 72
(1969)).

   [12] Notably, Lopez-Martinez does not argue that Agent
Vasquez’s questioning that led to this admission violated
Miranda. Instead, Lopez-Martinez contends that the prosecu-
tor’s statement broadly encompassed not only his pre-
custodial denial, but also his later, post-Miranda silence. Such
a reference, however, cannot be divined from a fair reading of
the transcript. The remark at issue was cabined to Lopez-
Martinez’s unequivocal denial that he had left anybody in the
desert and his failure to immediately alert Agent Vasquez that
the others might need help. The argument did not indict him
for any later silence. As such, it was not plain error for the
court to allow the prosecutor’s remarks.

  B.    POST-TRIAL

  By far the most troubling aspect of this case arose only
once the trial had concluded. After the jury was dismissed,
members of the judge’s staff found an envelope while they
                  UNITED STATES v. LOPEZ-MARTINEZ                    12685
were cleaning up the jury room. The envelope was unsealed,
and a piece of paper containing definitions of “reasonable
doubt” and “conspiracy” was sitting on top of it. There was
a “squiggle” on the envelope that the court believed might say
“Ellis, number 37.” The envelope and the piece of paper had
not been provided to the jury by the court. The court disclosed
the discovery to counsel the same day. Six days later Lopez-
Martinez’s counsel moved for a new trial.

   The district court held an evidentiary hearing, at which it
questioned all of the jurors regarding the document.3 At that
hearing, Juror Number 37, who had been an alternate juror
and was dismissed before deliberations began, stated that he
created the document based on his own internet research, and
that he brought it into the jury room on the day the jury began
its deliberations. The juror explained that he crafted the docu-
ment for his own edification and to be as prepared as possible,
and that he did not think he was violating “the spirit” of the
judge’s admonition against outside research. Juror Number 37
further stated that he never opened the sealed envelope, and
never discussed the envelope or its contents with the other
jurors. The other jurors all testified that they had never seen
the document. After the hearing, the district judge denied
Lopez-Martinez’s motion, finding that the jurors were “indi-
vidually and collectively credible,” and that “a new trial [was]
unnecessary because not a single juror participating in the
deliberations was even aware of the extrinsic information.”

   While the presence of this extrinsic evidence in the jury
room during deliberations is very unusual, this circumstance
does not warrant a new trial. We review de novo the denial
of Lopez-Martinez’s motion for a new trial, but review for
clear error the trial judge’s underlying factual findings.4 “Be-
   3
     We reject Lopez-Martinez’s argument that the district court’s decision
to hold an evidentiary hearing was error. That Lopez-Martinez would pre-
fer the court to make the decision in a vacuum, without the benefit of eval-
uating what actually happened, makes little common sense.
   4
     While the denial of a motion for a new trial is typically reviewed for
abuse of discretion, where the motion is based on juror misconduct — as
12686            UNITED STATES v. LOPEZ-MARTINEZ
cause of the trial judge’s unique opportunity to observe the
jurors during trial, to hear the defenses asserted, and to hear
the evidence, the judge’s conclusion about the effect of the
alleged misconduct deserves substantial weight.” United
States v. Saya, 

, 937 (9th Cir. 2001) (internal
quotations omitted).

   [13] The benchmark for a new trial when the jury obtains
or uses evidence that has not been introduced during trial is
if there is a reasonable possibility that the extrinsic material
“could have affected the verdict.” 

(internal quotations omitted). The threshold question we must
address, then, is a factual one: whether the jury obtained or
used evidence that was not introduced at the trial. If, as the
deliberating jurors all testified, none of them even saw the
paper with the alternative jury instructions on it, it is logically
impossible that this extrinsic evidence affected their verdict.
The trial judge, after holding an evidentiary hearing, deter-
mined that “not a single juror participating in the deliberations
was even aware of the extrinsic information.” This finding
was not clearly erroneous.

   Ten of the twelve jurors stated unequivocally that they did
not recall ever having seen the document in the jury room,
and that they had no memory of any of the other jurors look-
ing at it. With another juror, Juror Number 15, the judge had
the following exchange:

       THE COURT: Okay. Now, do you ever recall see-
     ing that [document] in the jury room?

        JUROR NO. 15: I — I think I — I remember
     reading them, but I don’t remember this particular
     page.

this one was — our review is de novo. See United States v. Saya, 

, 937 (9th Cir. 2001).
              UNITED STATES v. LOPEZ-MARTINEZ          12687
      THE COURT: Okay. Now, remember — now,
    remember, I gave you a set of jury instructions. Do
    you remember that? A thick set?

      JUROR NO. 15: (Nodding).

       THE COURT: Now, this is — this is something
    else. This was found in the jury room, was not given
    to you.

      So, the question is: Do you recall seeing that doc-
    ument in the jury room?

      JUROR NO. 15: No.

      THE COURT: Okay. And did you ever observe
    anyone else to have looked at that particular docu-
    ment?

      JUROR NO. 15: No, I didn’t.

Similarly, with Juror Number 20:

       THE COURT: Okay. Now, do you recall seeing
    those particular documents [the envelope and the
    piece of paper] in the jury room?

      JUROR NO. 20: Yes.

       THE COURT: Okay. Now, are those different
    from the instructions that I gave you?

      JUROR NO. 20: No, I don’t think so.

       THE COURT: Okay. Now, before I ask you how
    — how you saw them, do you recall when you left
    the jury — for your deliberations, I gave you a very
    thick set of jury instructions, is that correct?
12688           UNITED STATES v. LOPEZ-MARTINEZ
        [JUROR NO. 20]5: Yes.

        THE COURT: And those are different from the
     set of jury instructions I gave you. Do you under-
     stand that?

       JUROR NO. 20: In the fact that there’s not so
     many, you’re saying.

        THE COURT: The fact that those were by them-
     self. They were not part of the packet. They were
     brought in in a separate envelope.

        Have you ever seen that separate envelope or seen
     that particular jury instruction in the jury room, to
     the best of your knowledge?

        JUROR NO. 20: I don’t remember.

       THE COURT: Okay. Now, did you ever observe
     — did you ever observe anyone else looking at those
     two — at that document there?

        JUROR NO. 20: No.

        THE COURT: Okay. Now, you recall that my jury
     instructions were in a thick packet, they were all
     black and white copies, correct?

        JUROR NO. 20: Correct.

        THE COURT: And you’ll notice on page 2 of that
     there’s a colored portion on the bottom, is that right?

        [The court, at this points, realizes the juror is look-
 5
  The transcript erroneously says “THE DEFENDANT.”
               UNITED STATES v. LOPEZ-MARTINEZ           12689
    ing at a black and white photocopy, and instead
    gives the juror the colored original.]

      THE COURT: Do you ever recall seeing that doc-
    ument with the colored portion in the jury room?

       JUROR NO. 20: I don’t believe so.

   [14] As the transcript reflects, these jurors confused the
paper that Juror Number 37 brought in with him, and which
they were being shown by the court, with the packet of jury
instructions provided to them by the court during delibera-
tions. Once the court clarified that the piece of paper was not
part of that packet, both jurors testified that they did not
remember having seen it or seeing other jurors looking at it.
From this testimony, the trial judge reasonably found that
“[n]ot a single juror recalled seeing the extraneous informa-
tion before the evidentiary hearing.” We see no basis to dis-
agree with the trial judge’s finding that the jurors were
credible.

   [15] Lopez-Martinez correctly points out that this sequence
leaves unexplained exactly how the envelope containing the
alternate definitions came to be opened and by whom. As
much as it would be gratifying to know the who, what, when,
where, and why of how the envelope got opened, in the face
of the judge’s factual findings, it simply does not matter.
However the envelope got opened, given that none of the
jurors can even remember having seen the document, there is
no way it could have affected their deliberations. Lopez-
Martinez’s motion for a new trial was, therefore, properly
denied.

  C.   SENTENCING

   [16] Lopez-Martinez also appeals his sentence, arguing that
the judge failed to properly consider the need to promote
respect of law, justice, deterrence, and the protection of the
12690          UNITED STATES v. LOPEZ-MARTINEZ
public. Because the record reflects that the judge properly
considered all of the § 3553(a) factors and Lopez-Martinez’s
sentence was within the Guidelines range, we reject this argu-
ment and affirm Lopez-Martinez’s sentence. See 18 U.S.C.
§ 3553(a); United States v. Carty, 

, 992 (9th Cir.
2008) (en banc) (“A within-Guidelines sentence ordinarily
needs little explanation . . . .” ).

  AFFIRMED.