Opinion for the court filed by Circuit Judge HENDERSON.
Gerald F. Whitmore was convicted by a jury on firearm and drug charges. He appeals the firearm conviction on the ground that the district court committed reversible error in preventing him at trial from attacking the credibility of the arresting officer. Whitmore also claims that the court erred at sentencing in concluding that his prior conviction constituted a “crime of violence” within the meaning of the United States Sentencing Guidelines (U.S.S.G.). We conclude that the district court erred in prohibiting Whitmore from cross-examining the officer about certain instances of past conduct under Fed. R.Evid. 608(b). In doing so, the court deprived Whitmore of any realistic opportunity to challenge the credibility of the only witness who testified that Whitmore committed the firearm offense. That error was not harmless. We therefore reverse Whitmore’s firearm conviction and remand for a new trial on that charge. Because of this holding, we do not reach Whitmore’s sentencing claim.
*613 I. BACKGROUND
On June 20, 2002,' Whitmore was charged with one count of unlawful possession of a firearm and ammunition by a felon, in violation of 18 U.S.C. § 922(g)(1), and simple possession of a controlled substance (cocaine base), in violation of 21 U.S.C. § 844(a). On November 5, 2002, a jury convicted him on both counts. On January 31, 2003, the district court sentenced Whitmore to concurrent prison terms of 83 months on the firearm count and 12 months on the drug possession count, followed by a three-year term of supervised release.
Viewed in the light most favorable to the government,
see United States v. Graham,
Whitmore successfully eluded Russell but MPD Officer Efrain Soto, Jr., who was also patrolling the neighborhood in his police cruiser, spotted Whitmore and gave chase, first in his car and then on foot. Soto also noticed Whitmore’s right hand holding the right side of his jacket. While still in the cruiser, Soto saw Whitmore throw a gun towards an apartment building next to an alley Whitmore ran into. Shortly thereafter, Soto apprehended Whitmore. Once Russell caught up to assist, Soto found a gun in a window well of the apartment building. The weapon (with four rounds of ammunition, one of which was chambered) showed signs that it had been recently thrown against the building: a piece of brick was stuck in its sight, there were scuff marks on it and it was covered with masonry dust. The police found nothing in the right pocket of Whit-more’s jacket but did discover a small bag of cocaine base in his left pocket.
At trial Whitmore defended on the ground that Soto had fabricated the story about the gun and had planted the gun in the window well. Soto provided, almost exclusively, 1 the evidence connecting Whit-more to the gun and Whitmore therefore sought to attack Soto’s credibility in several ways. He first attempted to call three defense witnesses - Jason Cherkis, Bruce Cooper and Kennith Edmonds - to testify regarding Soto’s “character for truthfulness” under Fed.R.Evid. 608(a). Cherkis, a reporter with the City Paper, wrote an article in January 2000 reporting that Soto and three other MPD officers were the target of multiple complaints from residents of the MPD’s Sixth District, the district in which Whitmore was arrested. According to Whitmore, Cherkis would testify, based on conversations he had with his sources for the article, that Soto had a reputation as a liar. Cherkis moved to quash Whitmore’s subpoena on grounds of the First Amendment and the District’s reporter shield law. D.C.Code Ann. §§ 16^4701 et seq. Before trial, the court excluded Cherkis’s testimony under Fed. R.Evid. 608(a) because Cherkis was not personally acquainted with Soto and because the foundation of Cherkis’s testimony - interviews that he conducted for the *614 2000 article - was too remote in time to be relevant. Appellee’s App. at 26-28.
Bruce Cooper was a local criminal defense counsel who, Whitmore claimed, would testify regarding both Soto’s reputation for untruthfulness within what he called the “court community” and Cooper’s own opinion that Soto was untruthful. Whitmore proffered that Cooper would testify that several defense counsel thought Soto was a liar and that Cooper had the same opinion based on having tried many cases in which Soto was a government witness. The district court excluded Cooper’s reputation testimony because, even assuming the “court community” constituted a recognized community, Cooper did not know Soto’s reputation within the entire “court community” and did not live in Soto’s neighborhood. The court also rejected Cooper’s opinion testimony under Fed.R.Evid. 403 because it was “inherently biased,” Appellee’s App. at 359, and unduly prejudicial in that Cooper’s contacts with Soto arose from his representation of criminal defendants against whom Soto testified and because Cooper’s testimony would lead to additional delay - that is, the court would have to allow the government to explore the circumstances underlying Soto’s testimony in the other cases about which Cooper intended to testify.
Kennith Edmonds, whom Whitmore also sought to call as both a reputation and opinion witness, was an acquaintance of Soto who used to live in the neighborhood where Soto worked and who saw Soto regularly until roughly five years before the trial, when Edmonds moved away. Whitmore proffered that Edmonds would say that he still saw Soto a few times each week when Edmonds returned to his old neighborhood to visit his mother and still maintained contacts with others in the neighborhood who knew Soto. Edmonds’s proffered opinion evidence was based on two incidents: (1) Soto had participated in the arrest of a friend of his and, when Edmonds attempted to collect his friend’s property from the police, Edmonds was told that there was no property to collect; and (2) Soto and other officers wrongly arrested Edmonds for drug possession in 1995. The court excluded Edmonds’s reputation testimony because he had not lived in the neighborhood where Soto worked for some time; it excluded his opinion testimony because it questioned whether Soto was involved in the events on which Edmonds based his opinion. It also excluded Edmonds’s testimony in its entirety under Fed.R.Evid. 403, concluding that the minimal probative value of Edmonds’s evidence was outweighed by unfair prejudice, including the government’s resulting need to examine the events underlying Ed-monds’s testimony.
In addition to these three character witnesses, Whitmore also sought to impeach Soto by cross-examining him on three subjects: (1) a D.C. Superior Court judge’s finding that Soto had lied when Soto testified before him in a 1999 criminal trial; (2) the suspension of Soto’s driver’s license and Soto’s failure to report the suspension to his supervisors; and (3) Soto’s failure to pay child support. Regarding the first, the Superior Court judge had rejected Soto’s testimony that he had seen a bag of drugs with a blue line in the defendant’s hand. The judge found that testimony “palpably incredible,” Appellant’s App. at 73, and concluded that “Officer Soto lied.”
Id.
at 79. The judge therefore granted the defendant’s motion for acquittal. The U.S. Attorney’s Office subsequently investigated Soto for perjury but declined to prosecute him. It did, however, put Soto on a
“Lewis
list,” a watch list for officers under investigation.
See United States v. Bowie,
The government moved in limine to exclude cross-examination on the subject under Fed.R.Evid. 608(b) as well as Fed. R.Evid. 403, contending that the judge’s finding was only an allegation of misconduct and therefore not probative of Soto’s truthfulness and, in any event, was unfairly prejudicial. Whitmore argued for its admissibility as a specific instance of misconduct under Fed.R.Evid. 608(b) and as “motive” evidence under Fed.R.Evid. 404(b). According to lYhitmore, Soto had reason to lie in Whitmore’s case in order to curry favor with the government and rehabilitate himself following the local judge’s finding. The district court disagreed and barred cross-examination under Fed. R.Evid. 403, noting that the finding was not a perjury conviction, that the present jury might rely too heavily on the finding in making its own credibility determination regarding Soto and, finally, that any cross-examination would delay the trial and could confuse the jury because the government would have to be given the opportunity to explore the finding before the jury.
Whitmore’s other attempted impeachment matters involved the alleged suspension of Soto’s driver’s license and his alleged failure to pay child support. Whitmore sought to cross-examine Soto from a state document manifesting that Soto’s Maryland driver’s license had been suspended from 1998 to 2000 for failure to pay child support. Appellant’s App. at 107. MPD regulations require all officers to maintain a valid driver’s license and to notify their supervisor of any change in status. Id. at 110. Whitmore invoked both Fed.R.Evid. 608(b) and Fed.R.Evid. 404(b) in support of cross-examination on these subjects: (1) under Fed.R.Evid. 608(b), Soto’s alleged failure to report his suspended license and to make child support payments would reveal his inclination to dissemble and evade the law; and (2) under Fed.R.Evid. 404(b), Soto’s conduct gave him a motive to lie about 'Whit-more and the gun in order to secure a conviction in case his supervisor discovered his suspended license. The district court prohibited cross-examination on both subjects, concluding the document Whitmore intended to cross-examine from was hearsay and observing that it “d[id]n’t understand” Whitmore’s “bias argument.” Oct. 31, 2002 Trial Tr. (Tr.) at 232-234.
. In light of the trial court’s rulings, Whit-more presented no evidence in his defense and was limited to cross-examining the government witnesses about inconsistencies in their trial testimony. The jury convicted Whitmore on both counts. At sentencing the court concluded that 'Whit-more’s prior Maryland conviction for aggravated assault constituted a “crime of violence” as defined in U.S.S.G. § 4B1.2(a) and therefore calculated Whitmore’s base offense level pursuant to U.S.S.G. § 2K2.1(a)(2). It sentenced Whitmore to concurrent prison terms of 83 months on the firearm count and 12 months on the drug possession count, followed by a three-year term of supervised release.
II. DISCUSSION
The Sixth Amendment guarantees a defendant the right to present a defense by calling witnesses on his own behalf and 'by cross-examining the witnesses against him.
See Taylor v. Illinois,
Whitmore makes two challenges: one related to the exclusion of his proposed character witnesses under Fed. R.Evid. 608(a) and the other to the exclusion of his proposed cross-examination of Soto under Fed.R.Evid. 608(b). We review the district court’s evidentiary rulings for abuse of discretion,
see Wilson,
1. Character Witnesses
Fed.R.Evid. 608(a) allows a party to attack the credibility of a witness through reputation and opinion evidence of his character for truthfulness. 2 Whitmore complains that the district court erroneously excluded the testimony of three character witnesses he sought to call to attack Soto’s credibility. As noted earlier, they included: (1) Cherkis, a reporter who had written a newspaper article involving Soto in 2000; (2) Cooper, a local defense counsel who had represented defendants against whom Soto had testified; and (3) Edmonds, an acquaintance who had lived in the neighborhood where Soto worked. Whitmore wanted Cherkis to provide reputation evidence and Cooper and Edmonds both reputation and opinion evidence.
In order to offer reputation evidence under Fed.R.Evid. 608(a), a party must establish that the character witness is qualified by having an “acquaintance with [the witness],” his “community,” and “the circles in whkh he has moved, as to speak with authority of the terms in which generally [the witness] is regarded.”
Michelson v. United States,
While recognizing that the foundational requirement for
opinion
evidence regarding a witness’s character for truthfulness is less stringent than that for
reputation
evidence,
see Watson,
Whitmore contends that the foundational defects could have been highlighted by the government in cross-examining his character witnesses but were not severe enough to exclude the evidence altogether.
See Watson,
2. Cross-Examination of Soto
Fed.R.Evid. 608(b) allows a party to attack the credibility of a witness by cross-examining him on specific instances of past conduct.
4
Cross-examination pursuant to Fed.R.Evid. 608(b) is not confined to prior criminal convictions - they are governed by Fed.R.Evid. 609 - but the conduct must be probative of the witness’s character for truthfulness.
See
Fed. R.Evid. 608(b). It may not, however, be proven by extrinsic evidence. Id.;
United States v. Morrison,
*619 Whitmore contends that the district court erroneously prevented him from cross-examining Soto under Fed.R.Evid. 608(b) regarding three instances of past misconduct: (1) his testimony before the Superior Court judge in 1999; (2) the 1998 suspension of Soto’s Maryland driver’s license and his failure to report the suspension to his supervisors; and (3) Soto’s failure to make child-support payments. 5 The district court prohibited cross-examination as to the first instance under Fed.R.Evid. 403; with regard to Soto’s failure to report his suspended license and his failure to make child support payments, the court concluded that the document on which Whitmore relied to pursue the questioning was itself unreliable hearsay. We disagree. 6
Under Fed.R.Evid. 403, a court may exclude relevant evidence “if its probative value is substantially outweighed by the danger of unfair prejudice, confusion of the issues, or misleading the jury, or by considerations of undue delay, waste of time, or needless presentation of cumulative evidence.” “Rule 403 tilts,” however, “as do the rules as a whole, toward the admission of evidence- in close cases;” when “performing the balancing test required under Rule 403, ... the balance should be generally struck in favor of admission.”
United States v. Cassell,
Here the district court first determined that the probative value of any cross-examination regarding Soto’s testimony before the Superior Court judge would be slight because it involved an unrelated and dated matter and fell short of a perjury conviction. It then concluded, relying in part on
United States v. Lopez,
For his part, Whitmore contends that the proposed cross-examination was strongly probative of Soto’s character for untruthfulness and that, given the critical nature of Soto’s evidence against Whit-more, the district court should have allowed it. We agree. Nothing could be more probative of a witness’s character for untruthfulness than evidence that the witness has previously lied under oath. Indeed, as the Second Circuit observed - in a remarkably similar case (before the enactment of Fed.R.Evid. 608(b)) in which a party sought to cross-examine a “key witness” regarding a finding by another court
*620
that the witness had “ ‘intentionally g[iven] false testimony’”: “the rule seems to be well settled that although the opponent is not permitted to adduce extrinsic evidence that a witness lied on a previous occasion, he may nonetheless ask questions to that end.”
Walker v. Firestone Tire & Rubber Co.,
Relying on our holdings in
United States v. Morrison,
Moreover, neither
Morrison
nor
Bowie
supports the district court’s total rejection of Whitmore’s proposed cross-examination regarding Soto’s prior testimony, the judge’s finding and the United States Attorney’s Office’s subsequent investigation of Soto. In
Morrison
we rejected the defendant’s claim that he was entitled to cross-examine a government witness regarding the fact that the latter had been sued in state court, noting that “the mere
filing
of a complaint” - “regardless of whether the allegations in the complaint [were] true” - did not meet Fed.R.Evid.
*621
608(b)’s requirement that cross-examination be confined to conduct that is “ ‘probative of truthfulness or untruthfulness.’ ”
We also believe the district court erred in excluding the entire line of cross-examination on the ground that its probative value was substantially outweighed by the risk that the jury might blindly follow the prior judge’s lead or be otherwise distracted from the substance of Whitmore’s trial. The government relies on the First Circuit’s holding in
Lopez
and dicta in Bowie
7
to argue the exclusion of any cross-examination about the judge’s finding. Yet
Lopez
and the
Bowie
dicta stand only for the general proposition that extensive cross-examination regarding the judge’s finding would be overly prejudicial and neither case involved the cross-examination of the government’s
key
witness.
Lopez,
Turning to the district court’s denial of cross-examination regarding Soto’s suspended driver’s license and failure to pay child support, we also find error. The trial court precluded cross-examination on those matters on the ground that there was “no basis” for the cross-examination because Whitmore’s only support for them - the record from the Maryland Motor Vehicle Administration - was inadmissible hearsay. Tr. 234. Counsel, however, need only have “ ‘a reasonable basis for asking questions on
*622
cross-examination which tend to incriminate or degrade the witness,’ ” and “the general rule in such situations is that ‘the questioner must be in possession of some facts which support a genuine belief that the witness committed the offense or the degrading act to which the question relates.’ ”
United States v. Lin,
3. Error Not Harmless
Having determined that the district court erred in denying Whitmore the opportunity to cross-examine Soto about past misconduct pursuant to Fed. R.Evid. 608(b) and Fed.R.Evid. 403, we must determine whether the evidentiary rulings constituted harmless error.
See
Fed.R.Crim.P. 52(a) (“Any error ... that does not affect substantial rights must be disregarded.”). There are two different standards of review for harmlessness, “one for non-constitutional errors and one for errors of constitutional dimension.”
United States v. Powell,
Soto provided the sole and critical eyewitness evidence to support Whitmore’s firearm conviction. We are hard-pressed to understand the government’s claim that
*623
the proposed cross-examination would have “had only marginal evidentiary value,” Appellee’s Br. at 50, and we cannot ignore the potential impact of such a highly probative attack on Soto’s character for truthfulness.
Walker,
But the government argues that the court’s rulings, if erroneous, were harmless because Soto’s testimony was “amply corroborated by the other officers involved in the arrest” and Whitmore’s “defense theory was incredible.” Appellee’s Br. at 48-50. The government finds no safe harbor in either argument. First, the fact that Officer Russell testified that Whit-more ran when confronted by Russell is of little importance in light of the cocaine base he was carrying. That another officer testified the gun showed signs it had been recently thrown against the wall of a nearby building does not say anything about who threw it. There were no fingerprints on the weapon.
8
In fact, the only independent piece of evidence corroborating Soto’s testimony connecting Whit-more to the gun was Russell’s testimony that Whitmore was holding the right side of his jacket as he fled. Standing alone, this evidence would hardly sustain Whit-more’s conviction. Under these circumstances, the government has not shown that a reasonable jury would have put aside relevant, impeaching evidence about the government’s key witness and reached a similar verdict had it heard the excluded cross-examination.
See United States v. Foster,
Relying on our recent decision in
United States v. Powell,
III. CONCLUSION
For the foregoing reasons, we conclude the'district court committed reversiblfe error in prohibiting the cross-examination of Officer Soto as set forth above. The cumulative effect of prohibiting all three proposed lines of cross-examination was to *624 deprive Whitmore of any genuine opportunity to challenge the credibility of the only witness who testified that he possessed the gun in question. We cannot conclude that the error was harmless. We therefore vacate the judgment of conviction under 18 U.S.C. § 922(g)(1) (felon in possession of a firearm) and remand for a new trial on that charge. Whitmore’s conviction under 21 U.S.C. § 844(a) (simple possession of a controlled substance) remains unaffected. Because Whitmore’s sentencing challenge is predicated on his firearm conviction, we need not address it.
So ordered,.
Notes
. Although Officer Russell testified that Whit-more held his right hand close to his right side as he fled, Russell did not see him throw anything.
. Fed.R.Evid. 608(a) provides:
The credibility of a witness may be attacked or supported by evidence in the form of opinion or reputation, but subject to these limitations: (1) the evidence may refer only to character for truthfulness or untruthfulness, and (2) evidence of truthful character is admissible only after the character of the witness for truthfulness has been attacked by opinion or reputation evidence or otherwise.
. The district court also excluded Cherkis’s and Cooper’s testimony because neither lived in Soto’s community. Courts have rejected the notion, however, that reputation testimony is confined to the witness's residential community or that the character witness must physically reside in that community.
See, e.g., Wilson, 6
F.3d at 1239 (admitting reporter's testimony about witness’s reputation among people with whom he had worked and among his family because “a community doesn't have to be stable in order to qualify under the rule”);
United States v. Mandel,
. Fed.R.Evid. 608(b) provides:
Specific instances of the conduct of a witness, for the purpose of attacking or supporting the witnesses] character for truthfulness, other than conviction of crime as provided in rule 609, may not be proved by extrinsic evidence. They may, however, in the discretion of the court, if probative of truthfulness or untruthfulness, be inquired into on cross-examination of the witness (1) concerning the witnesses] character for truthfulness or untruthfulness, or (2) concerning the character for truthfulness or untruthfulness of another witness as to which character the witness being cross-examined has testified.
. Whitmore also asserts that cross-examination on these subjects was permissible under Fed.R.Evid. 404(b) to show that Soto had a motive to lie in Whitmore's trial to curry favor with (or avoid future investigation by) his MPD supervisors. Because we conclude that reversal is required for the reasons discussed in the text, we need not address this assertion.
. The district court did not conclude, and the government does not argue, that the proposed cross-examination would be impermissible under Fed.R.Evid. 608. Rather, the government argues only that it was within the district court's discretion to exclude this line of cross-examination.
. The
Bowie
court, again in the context of assessing a
Brady
violation involving a prior negative credibility determination by another judge in another matter, included a hypothetical dialogue among the court, the prosecutor and defense counsel about the scope of cross-examination regarding that determination.
. It had apparently been wrapped in rubber bands to prevent identification.
