Full opinion text
BENTON, Circuit Judge. A jury convicted Alfonso Rodriguez, Jr., of kidnapping Dru Kathrina Sjodin and transporting her across state lines, resulting in death. 18 U.S.C. § 1201(a)(1). The jury imposed a sentence of death. See 18 U.S.C. §§ 3591, 3593. Having jurisdiction under 28 U.S.C. § 1291 and 18 U.S.C. § 3595(a), this court affirms. I. Dru Sjodin left a mall in Grand Forks, North Dakota, on the afternoon of November 22, 2003. After she missed work that evening, a friend reported her absence to the police, who discovered her car in the mail’s parking lot with a knife sheath beside it. Sjodin’s phone-service provider, when contacted, told police her phone was “bouncing” off a cell tower near Crookston, Minnesota. Three days later, investigators found one of Sjodin’s shoes under a bypass near Crookston. Investigators interviewed persons in the surrounding area with convictions for kidnapping or sex offenses. Alfonso Rodriguez, Jr. — a Crookston resident and a Level III sex offender released from prison six months earlier — told police he traveled to Grand Forks on November 22 to visit the mall and see a movie. Police examined his car, which had small blood splatters in the back seat and a knife in the trunk matching the sheath found near Sjodin’s car. The movie Rodriguez claimed to have watched on November 22 was not playing at the mail’s movie theater that day. Sjodin’s body was found on April 17, 2004, in a drainage ditch outside of Crookston; her phone was nearby. Her body was naked below the waist, hands tied behind her back. Rope and remnants of a plastic bag encircled her neck. Her upper-body garments were pulled down off her shoulders. Police recovered hair and fiber samples from the body, which matched Rodriguez and his possessions. According to the autopsy, the most likely cause of death was asphyxiation or suffocation, a slash wound to the neck, or exposure to the elements. The government charged Rodriguez with kidnapping Sjodin and transporting her across state lines, resulting in death. 18 U.S.C. § 1201(a)(1). Seeking the death penalty, the government charged four statutory aggravating factors, 18 U.S.C. § 3592(c)(1), (4), (6), and (9). The jury convicted Rodriguez of the single count. The district court bifurcated penalty proceedings into an eligibility phase and a selection phase. During the eligibility phase, the jury found the government proved three statutory aggravating factors beyond a reasonable doubt: (1) 18 U.S.C. § 3592(c)(1), causing death during commission of another crime, kidnapping; (2) § 3592(e)(4), at least two prior felony convictions for infliction or attempted infliction of serious bodily injury; and (3) § 3592(c)(6), committing the offense in an especially heinous, cruel, or depraved manner. The jury found the government did not prove: (4) § 3592(c)(9), committing the offense after substantial planning and premeditation. During the selection phase, Rodriguez called 24 witnesses, the government six. Rodriguez submitted 30 mitigating factors; jurors found 25, including 19 unanimously. The government submitted one non-statutory aggravating factor — loss, injury, and harm to Dru Sjodin and her family, which the jury found unanimously. The jury recommended a sentence of death, which the district court imposed. See id. § 3594. Rodriguez appeals, challenging venue, jury composition and selection, evidentiary rulings, penalty-phase closing arguments, the 18 U.S.C. § 3592(c)(4) aggravating factor, penalty-phase jury instructions, and the constitutionality of the death penalty. II. Venue “In all criminal prosecutions, the accused shall enjoy the right to a speedy and public trial, by an impartial jury of the State and district wherein the crime shall have been committed.... ” U.S. Const, amend. VI. “[Wjhere a crime consists of distinct parts which have different localities the whole may be tried where any part can be proved to have been done.” United States v. Rodriguez-Moreno, 526 U.S. 275, 281, 119 S.Ct. 1239, 143 L.Ed.2d 388 (1999), quoting United States v. Lombardo, 241 U.S. 73, 77, 36 S.Ct. 508, 60 L.Ed. 897 (1916). Here, the crime consisted of distinct parts occurring in North Dakota and Minnesota, and venue would have been proper in either district. Fed. R.Crim.P. 18. A North Dakota grand jury indicted Rodriguez, who moved to change venue to Minnesota, citing pretrial publicity. This court examines denials of ehange-ofvenue motions based on pretrial publicity under a two-tier standard for presumed prejudice and actual prejudice. United States v. Blom, 242 F.3d 799, 803 (8th Cir.2001). Rodriguez argues: (a) the district court erred by not finding a presumption of prejudice in North Dakota, (b) jurors’ voir dire statements demonstrated actual prejudice, (c) Criminal Rule 21 required transfer of venue, and (d) by denying additional funds for a venue study, the district court violated Ake v. Oklahoma, 470 U.S. 68, 105 S.Ct. 1087, 84 L.Ed.2d 53 (1985). This court reviews denials of venue and Ake motions for abuse of discretion. United States v. Stanko, 528 F.3d 581, 584 (8th Cir.2008) (venue); United States v. Ross, 210 F.3d 916, 921 (8th Cir.2000) (Ake). A. Presumption of prejudice analysis A motion to change venue must be granted if “pretrial publicity was so extensive that a reviewing court is required to presume unfairness of constitutional magnitude.” Blom, 242 F.3d at 803 (quotations and citations omitted). In Irvin v. Dowd, the Supreme Court presumed prejudice when a newspaper received by 95 percent of local residents commented on the accused serial killer’s presumed guilt, prior crimes, lie-detector test failure, confession, and anticipated punishment. Irvin v. Dowd, 366 U.S. 717, 725-26, 81 S.Ct. 1639, 6 L.Ed.2d 751 (1961). To show a presumption of prejudice, Rodriguez cites extensive North Dakota media coverage, including 241 articles about the case in the Fargo Forum (some allegedly inflammatory); statements by public officials about the case; two public opinion polls, from September 2004 and February 2006; statements by 98 of 214 examined venirepersons indicating a belief in Rodriguez’s guilt; and, statements by serving jurors about public animosity toward Rodriguez. Denying the motion to change venue, the district court took several measures to reduce the risk of prejudice. The court moved the trial from Grand Forks to Fargo, 80 miles away, and excluded Grand Forks-area residents from the venire. The court assembled a 590-person jury pool, twelve times the normal size, and required jurors to answer a 121-question form, including detailed questions on their knowledge and beliefs about the case. Rodriguez received ten additional peremptory strikes, for 30 total. The court spent 21 days conducting voir dire. Reviewing the cited newspaper stories, the court concluded they were unlikely to unfairly prejudice the public against Rodriguez. This court’s decision in United States v. Blom, 242 F.3d 799 (8th Cir.2001), answers most of the presumed-prejudice arguments in this case. There, local media extensively reported prosecutors’ allegations that Blom kidnapped and murdered a female teenager. Tried on a federal weapons charge, Blom moved for change of venue, citing local media coverage. This court affirmed the denial of the motion, noting the district court moved the trial to a city within the state away from the crime site, excluded crime-area residents from the venire but expanded the venire to the whole state, assembled a jury pool three times the normal size, sent questionnaires to all prospective jurors, and increased the number of peremptory strikes for each side. Id. at 803-04. See also United States v. Allee, 299 F.3d 996, 1000 (8th Cir.2002) (finding no presumption of prejudice, despite 200 articles about the crime, when most news coverage was non-inflammatory and appeared two months-to-one year before trial). Rodriguez also cites statements by public officials. A U.S. Senator who sponsored “Dru’s Law” stated his hope that “justice will be done.” The Governor of Minnesota expressed his opinion, after the guilty verdict, that if the death penalty was ever appropriate, it was appropriate in this case. On this record, neither statement unfairly prejudiced Rodriguez. The only significant distinction between this case and Blom or Allee is the public opinion data. This court has expressed doubts about the relevance of such polls when reviewing rejected change-of-venue motions. See Shapiro v. Kauffman, 855 F.2d 620, 621 (8th Cir.1988) (declining, in a civil case, to attach significance to poll indicating defendant’s local popularity); United States v. Eagle, 586 F.2d 1193, 1195 (8th Cir.1978) (finding public opinion survey about attitudes toward Native Americans charged with high-profile killings irrelevant to unrelated case involving Native American defendants); United States v. Long Elk, 565 F.2d 1032, 1041 (8th Cir.1977) (noting the district court considered but declined to rely on a public opinion poll). At least three other circuits have declined to rely on public opinion polls when reviewing denials of motions for change of venue in criminal cases. See United States v. Campa, 459 F.3d 1121, 1145-46 (11th Cir.2006) (en banc) (district court did not err by refusing to rely on public opinion poll when it had methodological problems); United States v. Malmay, 671 F.2d 869, 875-76 (5th Cir.1982) (district court did not err by denying change-of-venue motion when public opinion poll revealed only general public awareness of the crime rather than widespread belief about defendant’s guilt); United States v. Haldeman, 559 F.2d 31, 64 n. 43 (D.C.Cir.1976) (trial judge had discretion to ignore “a poll taken in private by private pollsters and paid for by one side,” given adequacy of voir dire procedures). This court’s precedents do not require a district court to consider public opinion polls when ruling on change-of-venue motions. Even if these polls were considered, however, they do not demonstrate widespread community prejudice. The first poll, conducted in 2004, offers little insight into community views at the time of the 2006 trial. See Patton v. Yount, 467 U.S. 1025, 1032, 104 S.Ct. 2885, 81 L.Ed.2d 847 (1984) (noting the trial occurred four years after the initial media coverage “at a time when prejudicial publicity was greatly diminished and community sentiment had softened”). The second poll was conducted six months before Rodriguez’s trial in North Dakota’s Southeast Division. This poll showed that about 42 percent of the respondents strongly held an opinion of Rodriguez’s guilt, and the district court concluded that special voir dire protocols would screen out prejudiced jurors. The court also observed that media coverage had not been inflammatory, and that two years had passed since Sjodin disappeared. The district court did not abuse its discretion by denying the motion for change of venue based on presumed prejudice. B. Actual prejudice analysis Rodriguez next argues that voir dire revealed actual prejudice by some jurors. This court “independently evaluate^] the voir dire testimony of the impaneled jury in order to determine whether an impartial jury was selected, thus obviating the necessity for a change of venue.” Blom, 242 F.3d at 804 (citation omitted). Rodriguez first asserts that eleven jurors’ exposure to pretrial publicity demonstrates actual prejudice. By itself, exposure to pretrial publicity, however, does not establish prejudice. United States v. Bliss, 735 F.2d 294, 297-98 (8th Cir.1984) (“[T]he due process guarantee of trial by a fair and impartial jury can be met even where, as here, virtually all of the veniremen admit to some knowledge of the defendant due to pretrial publicity.”). Next, Rodriguez cites: (1) three serving jurors’ knowledge of his prior convictions, received through the media; (2) three serving jurors’ alleged opinions of his guilt, based on media accounts; and (3) five serving jurors’ statements that, after being called for jury service, they discussed the case with others and received opinions about Rodriguez’s guilt. 1. Jurors’ knowledge of prior convictions • Juror 3 testified that she “heard a little” about Rodriguez’s prior crimes, but stated that “if that’s not what the case is about, then that wouldn’t be what I would be considering.” • Juror 14 testified that she had heard Rodriguez previously committed some crimes, following which defense counsel told her the details of those crimes. Juror 14 then stated that she “would need to have all of the facts” before deciding Rodriguez’s guilt in this case. • Juror 15 stated that she did not think she had read about any criminal convictions but that, if informed of prior convictions, she would not automatically vote to convict or impose the death penalty. 2. Jurors’ pretrial opinions of guilt • Juror 3 testified that, having read some newspaper stories, “I guess you form somewhat of an opinion but it’s not — nothing is ground in my mind one way or the other.” When asked if she could put that opinion aside she replied, “I think so, yes.” • When asked by the court whether he had an opinion about Rodriguez’s guilt or innocence, Juror 8 stated: “No. I guess in the early stages when everything first happened I guess you assume guilty. But right now I guess you need to look at the evidence and see where it goes.” • Juror 11 indicated that, based on initial media accounts, he did believe that Rodriguez was guilty, but that he could put that opinion aside and require the government to prove its case beyond a reasonable doubt. 3. Jurors’ discussions with other people • Juror 2 stated that “probably a dozen” close friends and family had expressed their opinions about Rodriguez’s guilt, her two sons opined that Rodriguez “should be done away with,” but she herself did not “really have an opinion. I would like to hear the evidence.” • Juror 3 testified that several family members had expressed opinions about the case, but that “I don’t go by other people’s opinion.” • Juror 11 indicated that his wife and coworkers had expressed opinions about Rodriguez’s guilt and their desire for death to be imposed, but he also stated that he could put those opinions aside when serving on the jury. • Juror 13 testified that his boss believed Rodriguez was guilty, but that he would not feel any pressure to arrive at a guilty verdict because of his boss’s opinion. • Juror 16 noted that while she had expressed to her family sympathy for the victim’s family, such sympathy “absolutely ... cannot be” the basis of a guilty verdict. In Blom, all jurors “had at least some knowledge that Blom was connected with or accused of’ the publicized kidnapping. Blom, 242 F.3d at 804. This court found no actual prejudice because “[e]ach declared he or she could put aside all pretrial publicity, recognize the presumption of innocence in Blom’s favor, and render an impartial verdict based solely on the evidence presented at trial.” Id. As for jurors who expressed an initial impression of guilt, if the district court accepts assurances that they will set aside any preconceived beliefs, the court’s ruling is a credibility finding, which this court reviews for clear error. Id. at 805, citing Reynolds v. United States, 98 U.S. 145, 156-57, 25 L.Ed. 244 (1878). “Mere exposure to publicity or the formation of tentative impressions by some jurors is not enough to require a change of venue.” United States v. Harvey, 756 F.2d 636, 640 (8th Cir.1985). “The ultimate test is whether a juror has been exposed to pretrial publicity and, if so, whether he or she can set aside any impression or opinion resulting from that exposure and render a verdict based solely on the evidence presented at trial.” Id. The district court was not clearly erroneous in finding that the jurors’ statements, in context, do not establish actual prejudice. C. Criminal Rule 21(a) Rodriguez asserts that Rule 21(a) “grants a defendant even more protection against prejudicial pretrial publicity and community passion than does the constitutional due process standard.” The Rule states: “Upon the defendant’s motion, the court must transfer the proceeding against that defendant to another district if the court is satisfied that so great a prejudice against the defendant exists in the transferring district that the defendant cannot obtain a fair and impartial trial there.” Fed.R.Crim.P. 21(a). Rodriguez bases this argument on Marshall v. United States, 360 U.S. 310, 79 S.Ct. 1171, 3 L.Ed.2d 1250 (1959) (per curiam). There, the Supreme Court reversed a federal conviction when seven jurors read newspaper stories during trial about the defendant’s prior criminal conduct. Id. at 1172-73. Rodriguez also cites Chief Justice Burger’s concurring opinion in Murphy v. Florida, which commented on the Court’s supervisory powers in federal cases, and a district court decision granting a change-of-venue motion based on its reading of Rule 21(a). See Murphy v. Florida, 421 U.S. 794, 804, 95 S.Ct. 2031, 44 L.Ed.2d 589 (1975) (Burger, C.J., concurring); United States v. Tokars, 839 F.Supp. 1578, 1582-84 (N.D.Ga.1993). Rodriguez’s Rule 21(a) argument is unpersuasive. Neither the text of the Rule nor the Advisory Committee Note supports his interpretation. Marshall does not cite Rule 21, and that case involved juror exposure to news stories during, not before, trial. Chief Justice Burger’s concurrence in Murphy, which likewise does not cite Rule 21, offers less guidance than the Supreme Court’s more specific venue holdings. This court declines to follow the Tokars district court’s reading of Rule 21(a). D. Alleged violation of Ake v. Oklahoma The district court approved $7,500 for venue studies of North Dakota and Minnesota, but denied Rodriguez’s request for additional funding to study Minnesota. Rodriguez asserts that the denial of this request violates Ake v. Oklahoma, 470 U.S. 68, 105 S.Ct. 1087, 84 L.Ed.2d 53 (1985). “The decision of whether to fund an expert rests in the sound discretion of the trial court and we will not reverse absent an abuse of discretion.” United States v. Ross, 210 F.3d 916, 921 (8th Cir.2000). “[W]hen a defendant has made a preliminary showing that his sanity at the time of the offense is likely to be a significant factor at trial, the Constitution requires that a State provide access to a psychiatrist’s assistance on this issue if the defendant cannot otherwise afford one.” Ake, 470 U.S. at 74, 105 S.Ct. 1087. Ake analogizes psychiatric evaluations to other criminal defense rights — such as state-provided appeal transcripts and blood tests in paternity suits — but does not mention venue studies. Id. at 76, 105 S.Ct. 1087. The opinion does, however, state that “the consistent theme of these cases” is “[m]eaningful access to justice.” Id. at 77, 105 S.Ct. 1087. To establish an Ake violation, “the defendant must show a reasonable probability that an expert would aid his defense, and that denial of expert assistance would result in an unfair trial.” Little v. Armontrout, 835 F.2d 1240, 1244 (8th Cir.1987) (en banc). The Little court reversed a rape conviction based on the victim’s hypnosis-induced identification of the defendant. Id. at 1244-45. The state courts denied funding for a defense expert to challenge the hypnosis testimony. Reversing, this court found the expert might have shown the victim’s identification was influenced by “improper suggestion.” Id. at 1245. Assuming, without deciding, that the denial of funding for a venue study could violate Ake, Rodriguez must show by a reasonable probability that the additional venue-study funding would have aided his defense, and that the denial of funds resulted in an unfair trial. Neither of the two completed venue studies revealed prejudice sufficient to render a trial unfair, and the district court’s 21-day voir dire process screened out prejudiced jurors, consistent with Blom and Allee. The district court did not abuse its discretion by denying additional funds. III. Juiy composition and selection The district court assembled a 590-per-son venire drawn from across North Dakota, excluding the Grand Forks area. During voir dire, the court reduced this pool to 62 potential regular jurors and eight potential alternates. The court empaneled a jury of 12 persons and four alternates. Rodriguez challenges the district court’s jury selection plan, its rejection of two Batson challenges, and its exclusion of two venire members under Witt. A. Jury Selection Plan Rodriguez alleges that African-Americans and Hispanics were under-represented in the venire, in violation of Duren v. Missouri, 439 U.S. 357, 99 S.Ct. 664, 58 L.Ed.2d 579 (1979), and the Jury Selection and Service Act, 28 U.S.C. § 1861. Allegations of racial discrimination in jury pools involve mixed questions of law and fact, and receive de novo review. United States v. Morin, 338 F.3d 838, 843 (8th Cir.2003). 1. Duren “In all criminal prosecutions, the accused shall enjoy the right to a speedy and public trial, by an impartial jury of the State and district wherein the crime shall have been committed.... ” U.S. Const, amend. VI. “[T]he American concept of the jury trial contemplates a jury drawn from a fair cross section of the community.” Taylor v. Louisiana, 419 U.S. 522, 527, 95 S.Ct. 692, 42 L.Ed.2d 690 (1975). In Duren, the Supreme Court held that “systematic exclusion” of women from jury venires violates the constitution’s fair cross-section requirement. Duren, 439 U.S. at 360, 99 S.Ct. 664. To establish a Duren violation, Rodriguez must show: (1) that the group alleged to be excluded is a “distinctive” group in the community; (2) that the representation of this group in venires from which juries are selected is not fair and reasonable in relation to the number of such persons in the community; and (3) that this underrepresentation is due to systematic exclusion of the group in the jury-selection process. Id. at 364, 99 S.Ct. 664. Rodriguez asserts that the district court’s jury selection plan systematically excludes minorities by relying on lists of actual voters from the most recent presidential election. As African-Americans and Hispanics in North Dakota participated in the 2004 election at lower rates than the state’s whites, the proportion of minorities in the 590-person venire was lower than the overall proportion of minorities in North Dakota. The district court found Rodriguez met elements (1) and (2) of the Duren test. Relying on Eighth Circuit case law, the district court held that, to establish Duren element (3), Rodriguez had to show minorities faced obstacles to voting in North Dakota. See United States v. Greatwalker, 356 F.3d 908, 911 (8th Cir.2004) (per curiam); Morin, 338 F.3d at 844; United States v. Garcia, 991 F.2d 489, 492 (8th Cir.1993). “Absent proof that Native Americans, in particular, face obstacles to voter registration in presidential elections, [e]thnic and racial disparities between the general population and jury pools do not by themselves invalidate the use of voter registration lists and cannot establish the systematic • exclusion of allegedly underrepresented groups.” Morin, 338 F.3d at 844 (quotations omitted). Rodriguez offered no proof that minorities in North Dakota faced obstacles to voting. The Duren challenge fails under element (3). 2. Jury Service and Selection Act The JSSA requires that “grand and pet-it juries [be] selected at random from a fair cross section of the community in the district or division wherein the court convenes.” 28 U.S.C. § 1861. A court may dismiss an indictment based on a JSSA violation. Id. § 1867(a). This court “analyze[s] the [Jury Selection and Service] Act and the Sixth Amendment’s fair-cross-section requirement under identical legal standards.” United States v. Sanchez, 156 F.3d 875, 879 n. 3 (8th Cir.1998). See also United States v. Di Pasquale, 864 F.2d 271, 282 n. 15 (3d Cir.1988) (same); United States v. Miller, 771 F.2d 1219, 1227 (9th Cir.1985) (same); United States v. Test, 550 F.2d 577, 584-85 (10th Cir.1976) (same). Since the Duren challenge fails, so must the JSSA claim. B. Batson challenges The government peremptorily-struck Venireperson L.S., the only African-American among the 62 potential jurors, and Venireperson C.A., one of two Native Americans among the potential jurors. The district court rejected Batson challenges to both strikes. This court reviews the denial of Batson challenges for clear error. United States v. Bolden, 545 F.3d 609, 614 (8th Cir.2008). To establish a Batson violation: First, the defendant must make a prima facie case that the prosecution’s strike was motivated by race; second, the prosecution must offer a race-neutral reason for the strike; and third, taking into account all the evidence, the trial court must find whether or not the prosecutor was motivated by purposeful discrimination. United States v. Spotted Elk, 548 F.3d 641, 658 (8th Cir.2008), cert. denied, — U.S. -, 129 S.Ct. 1658, 173 L.Ed.2d 1028 (2009), citing Snyder v. Louisiana, 552 U.S. 472, 128 S.Ct. 1203, 170 L.Ed.2d 175 (2008). Rodriguez argues the district court failed to properly compare struck jurors with non-struck jurors. “If a prosecutor’s proffered reason for striking a black panelist applies just as well to an otherwise-similar nonblack who is permitted to serve, that is evidence tending to prove purposeful discrimination to be considered at Batson’s third step.” Miller-El v. Dretke, 545 U.S. 231, 241, 125 S.Ct. 2317, 162 L.Ed.2d 196 (2005). 1. Venireperson L.S. The district court found the government’s peremptory strike of L.S., the only African-American in the 62-person eligible-juror pool, established a prima facie Batson violation. The government offered three race-neutral reasons for striking L. S.: (1) she held a theater arts degree, supposedly indicating liberal bias; (2) she stated in her questionnaire that she did not trust police because they harassed minorities; and (3) her brother spent 22 months in jail for assaulting a law enforcement officer. The district court accepted the government’s reasons under the third step of the Batson test. Rodriguez challenges the government’s first reason, but not its second or third. Reviewing the voir dire record, this court concludes the district court did not clearly err by accepting the government’s race-neutral reasons for striking L. S., which do not apply just as well to an otherwise-similar non-minority who served on the jury. See United States v. Plumman, 409 F.3d 919, 928 (8th Cir.2005) (district court did not err by rejecting Batson challenge when “the prosecutor articulated multiple, nondiscriminatory reasons for exercising peremptory challenges” and defense counsel failed to establish the reasons were a pretext for race discrimination). 2. Venireperson C.A. The district court found a prima facie Batson violation based on the strike of Venireperson C.A., a member of the eight-person alternate juror pool and one of two Native Americans on the entire venire. During the second step of the Batson inquiry, the government gave three race-neutral reasons for striking C.A.: (1) his statement that capital punishment should be imposed only in extreme circumstances, (2) he is a college professor, an allegedly liberal profession; and (3) his brother spent time in prison for assault. Rodriguez attacks only one of the government’s proffered reasons as pretextual. The district court’s analysis under Batson step three, relying in part on C.A.’s family’s criminal history, was not clearly erroneous. Plumman, 409 F.3d at 928. C. Jurors excluded under Witt Rodriguez challenges the removal of two members of the venire based on their voiced concerns about the death penalty. “[A] potential juror may be excluded for cause based on his or her views on capital punishment only if those views would ‘prevent or substantially impair the performance of his duties as a juror in accordance with his instructions and his oath.’ ” United States v. Purkey, 428 F.3d 738, 750 (8th Cir.2005), quoting Wainwright v. Witt, 469 U.S. 412, 420, 105 S.Ct. 844, 83 L.Ed.2d 841 (1985). “We review a district court’s removal of death-scrupled venirepersons for an abuse of discretion.” Id. 1. Venireperson H.C. H.C. testified during voir dire: Q: Could you envision a case that you could fairly consider all the evidence and make a decision that the death penalty is appropriate? A: I don’t know. I’d probably — it would be questionable. I’d try to, but I really have trouble with the death penalty in any case, like I said, not even thinking about this ease. So my impartiality might be skewed in that way. A: It’s not just a feeling thing. It’s just — nothing to do with this case. I do have trouble with the death penalty. A: Okay. Well, just having anything to say or do about putting someone to death, you know, is bothersome, just that statement. And then also, you know, just throughout the year that someone has been put to death and then data comes out later on, whether it be years later, you know, someone was innocent, then the patient — not patient but the person has been put to death. Rodriguez asserts that H.C.’s testimony indicates he could follow the court’s instructions, and thus was wrongfully excluded in violation of Adams v. Texas, 448 U.S. 38, 50-51, 100 S.Ct. 2521, 65 L.Ed.2d 581 (1980). In Adams, the Supreme Court reversed the death penalty when Texas courts excluded prospective jurors “who stated that they would be ‘affected’ by the possibility of the death penalty, but who apparently meant only that the potentially lethal consequences of their decision would invest their deliberations with greater seriousness and gravity or would involve them emotionally.” Id. at 49, 100 S.Ct. 2521. “But neither nervousness, emotional involvement, nor inability to deny or confirm any effect whatsoever is equivalent to an unwillingness or an inability on the part of the jurors to follow the court’s instructions and obey their oaths, regardless of their feelings about the death penalty.” Id. at 50,100 S.Ct. 2521. Venireperson H.C.’s testimony indicated he would be more than simply “affected” by voting to impose the death penalty. He stated that his “impartiality might be skewed,” that he had “trouble” with the death penalty, and that the penalty was “bothersome” because of post-execution exonerations. The district court did not abuse its discretion by removing H.C. under Witt. See United States v. Nelson, 347 F.3d 701, 711-12 (8th Cir.2003) (finding the district court did not err by removing prospective jurors under Witt when “the record reveals that each of the three venirepersons would have had a great reluctance if not an actual inability to vote in favor of imposing the death penalty.”). 2. Venireperson G.B. G.B. testified during voir dire: A: I’ve been a Lutheran Christian now since 1984 and I’ve tried to abide by the different — of the understanding of the church, first what the church believes on the death penalty. I know what the church believes on the death penalty is that they are against it. ... But I suppose that I could agree with those cases that do cry out for the death penalty in the first instance if it rises to a political — to making a political statement such as the death penalty for somebody like Hitler or Stalin or a person in Bosnia or— Q: Genocide? A: (Nods head.) Or some of that nature. Q: You’ve described the categories that you think are appropriate for the death penalty, correct? A: (Nods head.) Q: And you’ve gone through a number of them. I think you said mass murder, genocide, et cetera, et cetera, that we went through. Are there other categories that you would fit into that we missed that we didn’t go over? ... A I don’t think. I suppose my own understanding of eases that cry out for the death penalty would have to be not just one-on-one but would have to be more than, for example, as a serial case. Q: It sounds like you’ve arrived at yourself — for yourself a strong ethical and moral sense of the death penalty; that you’ve given it some thought over time. Would you agree? A. Yes. It’s not only my own but it’s in conjunction with the church as well. Venireperson G.B. repeatedly affirmed his deeply-held moral opposition to the death penalty, providing exceptions only for politically-motivated and serial killer cases. The district court did not abuse its discretion by removing him under Witt. See United States v. Moore, 149 F.3d 773, 780 (8th Cir.1998) (no abuse of discretion to exclude, under Witt, jurors who “expressed serious doubt as to their ability to consider imposition of the death penalty”). IV. Evidentiary challenges Rodriguez challenges evidentiary rulings in the guilt and penalty phases. He appeals: (a) the admission, during the guilt phase, of acid-phosphate evidence under Fed.R.Evid. 702; (b) the admission, during the guilt phase, of two prior sexual assault convictions under Fed.R.Evid. 413; and (c) testimony, during the penalty phase, of victim-impact witnesses. This court reviews evidentiary rulings for abuse of discretion. United States v. James, 564 F.3d 960, 963 (8th Cir.2009). A. Guilt phase: acid-phosphate testing The district court permitted a government pathologist to testify, over objection, about the results of acid-phosphate tests conducted on Dru Sjodin’s body, indicating the presence of semen in her vagina and cervix. Rodriguez argues this testimony violates Daubert v. Merrell Dow Pharm., Inc., 509 U.S. 579, 113 S.Ct. 2786, 125 L.Ed.2d 469 (1993). This court reviews the district court’s expert-witness rulings for abuse of discretion. Polski v. Quigley Corp., 538 F.3d 836, 838 (8th Cir. 2008). Daubert holds that Fed.R.Evid. 702 supersedes the expert witness standard of Frye v. United States 293 F. 1013, 1014 (D.C.Cir.1923). Daubert, 509 U.S. at 589, 113 S.Ct. 2786. If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise, if (1) the testimony is based upon sufficient facts or data, (2) the testimony is the product of reliable principles and methods, and (3) the witness has applied the principles and methods reliably to the facts of the case. Fed.R.Evid. 702. “Faced with a proffer of expert scientific testimony ... the trial judge must determine at the outset, ... whether the expert is proposing to testify to (1) scientific knowledge that (2) will assist the trier of fact to understand or determine a fact in issue.” Daubert, 509 U.S. at 592, 113 S.Ct. 2786. To determine whether a testimony is “scientific knowledge,” the court considers four non-exclusive factors: (1) whether the theory or technique “can be (and has been) tested,” (2) “whether the theory or technique has been subjected to peer review and publication,” (3) “the known or potential rate of error,” and (4) “general acceptance” of the theory or technique. Id. at 593-94, 113 S.Ct. 2786. “‘General acceptance’ is not a necessary precondition to the admissibility of scientific evidence under the Federal Rules of Evidence, but the Rules of Evidence— especially Rule 702 — do assign to the trial judge the task of ensuring that an expert’s testimony both rests on a reliable foundation and is relevant to the task at hand.” Id. at 597, 113 S.Ct. 2786. “Pertinent evidence based on scientifically valid principles will satisfy those demands.” Id. The district court conducted a Daubert hearing on acid-phosphate testing. Permitting the pathologist’s testimony, the court noted that Rodriguez’s own expert acknowledged that the government pathologist’s test properly detects the presence of acid phosphate; that forensic labs across the country use acid-phosphate levels to indicate semen, and use the same cut-off levels as the government pathologist; and that while there is uncertainty about what acid-phosphate levels would be normal for a corpse, many pathologists share the government pathologist’s view of the reliability of the test, and any doubts go to the weight, not reliability, of the opinion. Challenging the testimony, Rodriguez first asserts the acid-phosphate testimony was based on the pathologist’s own experience, rather than peer-reviewed research. Daubert emphasizes that while peer-reviewed publication is a factor, “in some instances well-grounded but innovative theories will not have been published.” Id. at 593, 113 S.Ct. 2786. The government’s expert, a licensed medical doctor with three decades’ experience, became the chief examiner of the Hennepin County Medical Examiner’s office in 1985. He regularly participates in criminal investigations, including sex crimes, and testifies at trials. The pathologist did not invent acid-phosphate testing; he testified to attending national medical conferences and reviewing scientific literature on the topic. The test results are based on scientific methods and data, and assist the jury in its fact-finding. The district court did not abuse its discretion by admitting the acid-phosphate test results. Rodriguez next challenges the factual basis of the pathologist’s conclusion that acid-phosphate tests show semen deposits were made within 24-to-36 hours of Sjodin’s death. The pathologist stated that acid-phosphate levels were elevated in her vagina and cervix and that, in a living person, elevated levels drop to normal within 24-to-36 hours of the semen’s deposit. Because Sjodin’s body was covered in snow until its discovery, the pathologist testified that “the cold environment has to be taken into account regarding the preservation of the specimens we found at the sexual assault exam.” Cross-examined about the timing of this process, he stated: The process continues or is the same in a deceased individual only much slower. Therefore, if you use the same process taking place in a deceased individual as in a living individual, you can say the enzyme will break down over a more slower period of time. And I think some of the literature reports it going out as far as four to five days depending on the reports you read. Rodriguez asserts that the district court erred by allowing this testimony, claiming the time-frame testimony was unreliable. The pathologist based his testimony on acid-phosphate measurements in living people. He acknowledged there could be uncertainty about the factual basis of the timing of the chemical process in a corpse. [T]he factual basis of an expert opinion goes to the credibility of the testimony, not the admissibility, and it is up to the opposing party to examine the factual basis for the opinion in cross-examination. Questions of an expert’s credibility and the weight accorded to his testimony are ultimately for the trier of fact to determine. Only if an expert’s opinion is so fundamentally unsupported that it can offer no assistance to the jury must such testimony be excluded. Arkwright Mut. Ins. Co. v. Gwinner Oil, Inc., 125 F.3d 1176, 1183 (8th Cir.1997) (citations and quotations omitted). Rodriguez’s challenge — developed with thorough cross-examination — goes to credibility, not admissibility. The court did not abuse its discretion by allowing the testimony. Rodriguez also attacks the district court’s characterization of the views of the government pathologist and Rodriguez’s expert as two schools of thought on acid-phosphate testing. Instead, Rodriguez asserts, only his expert’s position is supported by scientific literature. This argument is contradicted by the testimony of Rodriguez’s expert, who acknowledged widespread support among American scientists for the government pathologist’s approach. Admission of the pathologist’s testimony was not an abuse of discretion. B. Guilt phase: Rule 413 convictions “In a criminal case in which the defendant is accused of an offense of sexual assault, evidence of the defendant’s commission of another offense or offenses of sexual assault is admissible, and may be considered for its bearing on any matter to which it is relevant.” Fed.R.Evid. 413(a). The district court admitted, during the guilt phase, evidence of two prior convictions under Rule 413. Rodriguez asserts Rule 413 is unconstitutional, in violation of the Due Process Clause, by not expressly incorporating Rule 403’s prohibition against admission of unfairly prejudicial evidence. See Fed.R.Evid. 403; U.S. Const, amend. V. This court has ruled, however, that Rule 403’s relevance-prejudice balancing test applies to evidence admitted under Rule 413. United States v. Mound, 149 F.3d 799, 800-801 (8th Cir.1998). Mound forecloses the constitutional challenge to Rule 413. Rodriguez also contends the district court abused its discretion by admitting evidence under Rule 413. During the guilt phase, the government sought to introduce evidence of four prior sexual assaults— Minnesota state convictions 5438, 5447, and 6192, and a charged count on which Rodriguez was acquitted. The government argued that all four incidents show a modus operandi of approaching young women, when alone, and using violence (or the threat of violence) in an actual or attempted sexual assault. Rule 413 permits evidence of relevant “sexual assaults.” A relevant sexual assault is one committed in a manner similar to the charged offense. United States v. Crawford, 413 F.3d 873, 875-76 (8th Cir.2005). The district court admitted evidence of the 5438 and 5447 convictions under Rule 413, but excluded evidence of the 6192 conviction and the acquitted count. The court reasoned that Rodriguez’s conduct in the 6192 case showed a kidnapping attempt, not a sexual assault, and thus was insufficiently similar and therefore not relevant. Applying Rule 403, the court excluded evidence of the acquitted count, concluding it is unfairly prejudicial to admit evidence of a crime where the jury did not convict. The court admitted the 5438 and 5447 convictions under Rule 413, allowing the victims to testify about Rodriguez’s conduct. In both cases, Rodriguez approached a young woman by herself, forced her into a vehicle under threat of violence, and sexually assaulted her. Here, the government alleged Rodriguez approached Sjodin while alone in a parking lot, abducted her at knife point, forced her into a car, and sexually assaulted her before murdering her. This court addressed a similar Rule 413 challenge in United States v. Horn, 523 F.3d 882, 888 (8th Cir.2008). There, this court affirmed the admission, under Rule 413, of a prior rape conviction. Id. Despite significant age differences between the victim of the prior conviction and those of the two charged offenses, all incidents involved sexual assaults of unconscious victims where the attacks ceased when the victims reacted. Id. Like the Horn conviction, the 5438 and 5447 convictions involved conduct similar to the charged offense here. The district court did not abuse its discretion by admitting convictions 5438 and 5447 under Rule 413. C. Penalty phase: victim-impact testimony Rodriguez asserts that the government’s victim-impact evidence, introduced during the penalty phase, violates the Due Process Clause, the Federal Death Penalty Act (FDPA), and the district court’s order. See U.S. Const. amend. V; 18 U.S.C. §§ 3591, 3592, 3593. This court reviews de novo constitutional challenges and questions of statutory interpretation. United States v. May, 535 F.3d 912, 915 (8th Cir.2008), cert. denied, — U.S. -, 129 S.Ct. 2431, 174 L.Ed.2d 229 (2009). Under the FDPA, the government may prove, to justify a death sentence, “factors concerning the effect of the offense on the victim and the victim’s family,” including “oral testimony, a victim impact statement that identifies the victim of the offense and the extent and scope of the injury and loss suffered by the victim and the victim’s family, and any other relevant information.” 18 U.S.C. § 3593(a). “Evidence ‘about the victim and about the impact of the murder on the victim’s family is relevant to the jury’s decision as to whether or not the death penalty should be imposed [and t]here is no reason to treat such evidence differently than other relevant evidence is treated.’” Bolden, 545 F.3d at 626, quoting Payne v. Tennessee, 501 U.S. 808, 827, 111 S.Ct. 2597, 115 L.Ed.2d 720 (1991). “However, admission of evidence ‘so unduly prejudicial that it renders the trial fundamentally unfair’ violates the Due Process Clause.” Id., quoting Payne, 501 U.S. at 825, 111 S.Ct. 2597. Permitting some victim-impact testimony, the district court limited it to factual statements subject to cross-examination, rather than statements of love or emotion. The government called six victim-impact witnesses, including three family members. Rodriguez contends that several statements contain improper expressions of emotion. The challenged comments include testimony about Sjodin’s good nature and popularity, her sorority sisters’ reactions when her body was found, and a non-family member’s impressions about the effect of the crime on Sjodin’s family. Her father testified about the last time he saw his daughter, and not working for five months after her disappearance in order to search for her. Sjodin’s stepfather discussed the impact of the crime on him and his wife, including work-related disruptions. Sjodin’s mother spoke about her good nature and her relationship with her brother. In United States v. Nelson, the government presented six victim-impact witnesses, including three family members. United States v. Nelson, 347 F.3d 701, 712-13 (8th Cir.2003). “A fair summation of their collective testimony is that the witnesses provided emotional and, on occasion, tearful testimony about Pamela and the impact of her murder on their lives.” Id. at 713. This court affirmed the penalty, noting that victim-impact testimony was neither quantitatively nor qualitatively overwhelming. Id. at 713-14. Here, the government presented six victim-impact witnesses, including three family members. The testimony was, on the whole, factual; witnesses explained the effect of Sjodin’s abduction and murder on their lives. Although the record shows some testimony was emotional, Nelson instructs that a district court does not abuse its discretion by denying a mistrial motion when victim-impact testimony has some emotional content. See id. Rodriguez himself presented numerous mitigation witnesses who testified about the value of his life and the emotional pain his execution would cause them. Reviewing the record, this court concludes that victim-impact testimony was not overwhelming, and any testimony that improperly conveyed emotion was harmless error. See United States v. Paul, 217 F.3d 989, 1002 (8th Cir.2000) (rejecting challenge to victim-impact testimony and noting that the defendant “was also able to present extensive mitigating evidence through the testimony of his mother”). Rodriguez also objects to the victim’s father shaking hands with the prosecutor in the presence of the jury, immediately after the father’s testimony. This court has not previously considered whether a defendant is unfairly prejudiced by a prosecutor shaking hands with a witness in the jury’s presence. The Ninth Circuit addressed this issue in United States v. Rude, 88 F.3d 1538, 1549 (9th Cir.1996). Finding no error, that court observed “our research revealed no case suggesting it,is improper for a prosecutor, without more, simply to shake hands with a witness upon the close of his testimony in the jury’s presence.” Id. “A prosecutor’s open handshake with a witness neither lends governmental imprimatur to his testimony nor personally assures the jury of its credibility.” Id. A prosecutor may not vouch for the veracity of government witnesses’ testimony. See United States v. Kenyon, 481 F.3d 1054, 1066 (8th Cir.2007) (“Improper vouching may occur when the government ... refers to facts outside the record or implies that the veracity of a witness • is supported by outside facts that are unavailable to the jury.”). Here, however, the handshake did not improperly bolster the witness’s testimony, or suggest that the Sjodin family desired a sentence of death. V. Government’s penalty-phase closing argument Rodriguez challenges a variety of statements in the government’s penalty-phase closing argument. To obtain reversal for prosecutorial misconduct, a defendant must show the prosecutor’s remarks were improper, and that such remarks prejudiced the defendant’s rights in obtaining a fair trial. United States v. Two Elk, 536 F.3d 890, 906 (8th Cir.2008). A. Relevance of mitigating factors Rodriguez contends that, several times in closing, the government misled the jury about the relevance of mitigating factors. “[Sentencing juries must be able to give meaningful consideration and effect to all mitigating evidence that might provide a basis for refusing to impose the death penalty on a particular individual, notwithstanding the severity of his crime or his potential to commit similar offenses in the future.” Abdul-Kabir v. Quarterman, 550 U.S. 233, 246, 127 S.Ct. 1654, 167 L.Ed.2d. 585 (2007). “[T]he sentencer in capital cases must be permitted to consider any relevant mitigating factor.... ” Eddings v. Oklahoma, 455 U.S. 104, 112, 102 S.Ct. 869, 71 L.Ed.2d 1 (1982). “Relevant mitigating evidence is evidence which tends logically to prove or disprove some fact or circumstance which a fact-finder could reasonably deem to have mitigating value.” Tennard v. Dretke, 542 U.S. 274, 284-85, 124 S.Ct. 2562, 159 L.Ed.2d 384 (2004) (citations omitted). See Smith v. Texas, 543 U.S. 37, 44, 125 S.Ct. 400, 160 L.Ed.2d 303 (2004) (“petitioner’s IQ scores and history of participation in special-education classes” were proper mitigating factors). Rodriguez first challenges this statement: Ask yourself what has the defense proven that actually has the power to change what the Defendant did in this case and erase who he is? And Judge Erickson just told you as to those mitigating factors where the burden lies .... [then, six transcript pages later] .... For the first time in this trial the law now says the defense has a burden of proof, and if you look at it closely, the burden has two components, as Judge Erickson’s instructions bear out. No mitigating information goes on the scale unless the defense meets its proof burden and you first reach a couple of conclusions. The burden of proving mitigation is on the defense to show the mitigation allegation is factually proven to the greater weight of the evidence. Also, the information has to be shown that the information mitigates in this case. Whether proven or not, does it mitigate, tend to lessen the severity in this case? A defense proposal for mitigation or mitigation that you find is only qualified to go on the decision scale if you answer yes for both of those mitigation questions, and then there’s a third issue, what weight do you want to give it? If either of those first two is not proven, either factually or that it mitigates, then you don’t have to give further consideration to that proposed factor. Rodriguez also challenges several statements where the government discussed the proposed mitigating factors. The government argued, for instance: We heard that the Defendant was a colicky baby, he was one of the poor kids in school, some kids teased him, and he is said to have encountered racism and sexual abuse, as did his sisters. Very serious matters. He inherited a benign hand tremor from his father, and he would rather have lived in Texas than Minnesota. Perhaps these factors would mitigate the Defendant getting into a fístfíght with one of the people who wronged him long ago, but what could it have to do with a 22-year-old girl the Defendant spotted in a mall, lusted after, kidnapped, assaulted and raped, and finally killed on November 22nd, 2003? No matter what the Defendant thinks he would change about his life, everyone agrees he is capable of choosing for himself. There’s nothing in the law that allows him to choose to do what he did to Dru Sjodin and his other victims, and there is nothing that says you are required to agree to it by way of his mitigation claims. Rodriguez asserts these comments improperly directed the jury to consider mitigation evidence only if it has a “nexus” to the crime. The FDPA authorizes a jury to impose a death sentence “after consideration of the factors set forth in section 3592.” 18 U.S.C. § 3591(a). Section 3592 lists both mitigating and aggravating factors. See id. § 3592(a), (c). “The government and the defendant shall be permitted to rebut any information .received at the hearing, and shall be given fair opportunity to present argument as to the adequacy of the information to establish the existence of any aggravating or mitigating factor, and as to the appropriateness in the case of imposing a sentence of death.” Id. § 3593(c). “The burden of establishing the existence of any mitigating factor is on the defendant, and is not satisfied unless the existence of such a factor is established by a preponderance of the information.” Id. Further, “as long as the jurors are not told to ignore or disregard mitigators, a prosecutor may argue, based on the circumstances of the case, that they are entitled to little or no weight.” United States v. Johnson, 495 F.3d 951, 978 (8th Cir. 2007), cert. denied, — U.S. -, 129 S.Ct. 32, 172 L.Ed.2d 46 (2008). Rodriguez had the burden of proving mitigating factors. 18 U.S.C. § 3593(c). The government may dispute those factors, and argue they should receive little or no weight. Id.-, Johnson, 495 F.3d at 978. The first challenged remarks, quoted above, accurately state the law: Rodriguez had to prove mitigating factors; the jury should consider only those mitigating factors proved by a preponderance of the evidence; and the jury could decide that any mitigating factors, even if proved, are sufficiently outweighed by aggravating factors. The second challenged remarks do not direct jurors to disregard mitigating factors because no nexus links them to the killing. Rather, the prosecutor argued that, despite Rodriguez’s troubled past, “he is capable of choosing for himself’ and has free will. This argument is permissible. See Johnson, 495 F.3d at 979 (finding no error when “[t]he prosecutor was arguing ... that she [the defendant] had free will and an opportunity to make the right choices, her difficult childhood notwithstanding.”). B. Alleged misstatement of law Rodriguez contends the government improperly argued that Rodriguez would receive a life sentence for kidnapping alone, and that a death sentence was necessary to punish him for the murder. The government argued that Rodriguez “could get the same punishment,” a life sentence, if he only kidnapped Sjodin, transported her across state lines, and let her go. The district court sustained Rodriguez’s objection to this and a similar comment. Cf. Rodden v. Delo, 143 F.3d 441, 447 (8th Cir.1998) (“In context, the prosecutor’s statements about the second murder being free urged the jury to impose additional punishment for the additional crime.”). The government misstated the law, Rodriguez asserts, as the jury could impose either life imprisonment or death for a kidnapping resulting in death. See 18 U.S.C. § 1201(a). The district court sustained his objection, however, and instructed the jury on its sentencing options. On this record, Rodriguez was not unfairly prejudiced by the remarks, and the district court did not abuse its discretion by denying the motion for a mistrial. See United States v. Boesen, 541 F.3d 838, 847 (8th Cir.2008) (district court did not abuse its discretion by denying mistrial when it sustained defense objection to prosecutor’s statement). C. Impact on the Rodriguez family Rodriguez argues the government improperly directed the jury to disregard the impact of a death sentence on the Rodriguez family. The prosecutor stated: This is the time for punishment. Punishment. And let me caution you respectfully, and I mean this respectfully, the issue of punishment for the Defendant is not an issue of how it affects his family, not under the law. The district court overruled Rodriguez’s objection, instructing the jury: I have instructed this jury on what the mitigating factors are alleged and if proven what they may consider and what weight they may assign to it. This is an argument. I’ll overrule the objection and instruct the jury to any arguments that are made by either counsel should be taken in light of the instructions that I have given. The prosecutor continued: The Rodriguez family is entitled to the sadness that they have expressed for the Defendant. They gave this Defendant every chance they could across the many years. But his choices have brought them here to this place. And when you consider the Defendant’s list of proposed mitigation, the United States respectfully urges you to conclude that the pain that his intentional acts have caused his family should not be allowed to weigh in his favor now; that he could benefit from what he has caused would be a gross injustice. The FDPA permits a defendant to propose “any mitigating factor.” 18 U.S.C. § 3592(a). Rodriguez proposed six mitigating factors addressing the emotional pain different family members would suffer if he were executed. The jury instructions explained: “you must consider whether the aggravating factors that you unanimously found to exist, both statutory and non-statutory, sufficiently outweigh any mitigating factors that you found ... so that a sentence of death is justified.” The first quotation, read alone, directs that family-impact mitigating factors are irrelevant “under the law.” A prosecutor errs by directing the jury to ignore a proposed mitigating factor. See Bolden, 545 F.3d at 630 (“[A]s long as the jurors are not told to ignore or disregard mitigators, a prosecutor may argue, based on the circumstances of the case, that they are entitled to little or no weight.”) (citation omitted). In the context of the entire exchange — the court’s instruction to the jury when overruling the objection, and the government’s renewed argument — the government’s argument is clearer. The prosecutor recognized the pain that an execution would cause the Rodriguez family, but argued that such pain should receive little weight when determining the appropriate penalty. This argument is permissible. The jury’s penalty-phase verdict shows it did not ignore the family-impact mitigation factors. It unanimously found that six members of Rodriguez’s family “will suffer emotional pain if Alfonso is executed.” Weighing these factors against the aggravating factors, however, the jury imposed a death sentence. This court concludes that, when read in context, the prosecutor’s comments were not improper. Even if the first comment is taken in isolation, however, Rodriguez’s right to a fair trial was not affected. In response to the objection, the court focused attention on the jury instructions, which direct the jury to consider each proposed mitigation factor and to balance all factors. Finally, the jury’s verdict, which found six family-impact mitigation factors, indicates the jury did not erroneously disregard the factors as irrelevant “under the law.” D. References to plea offer The district court admitted Rodriguez’s offer to plea guilty, in return for a life sentence, as a proposed mitigating factor showing acceptance of responsibility. See 18 U.S.C. § 3592(a) (When imposing sentence, the jury may consider “any mitigating factor,” including “[ojther factors in the defendant’s background, record, or character or any other circumstance of the offense that mitigate against imposition of the death sentence.”). No juror found that, by offering to plead guilty, Rodriguez accepted responsibility for the crime. The court ruled