OPINION OF THE COURT
Kenneth “Malik” Williams appeals from his conviction following trial for conspiracy to distribute cocaine and cocaine base, and possession of a firearm in furtherance of a drug trafficking offense. Williams also appeals his sentence of 420 months in prison. Regarding his conviction, Williams argues that the District Court erred in failing tо provide adequate jury instructions as to “multiple conspiracies” and as to the firearm charge. Williams also argues that the evidence was insufficient for conviction on the firearm charge, and that the District Court should not have prohibited Williams
*445
from cross-examining a key prosecution witness about his statement that he had nevеr committed murder. Lastly, Williams argues that his case should be remanded for resentencing in accordance with the Supreme Court’s opinion in
United States v. Booker,
BACKGROUND
In October 2002, Williams was indicted along with thirty-six co-defendants for conspiracy to distribute cocaine and cоcaine base. Williams was also charged with possession of a firearm in furtherance of a drug trafficking crime pursuant to 18 U.S.C. § 924(c)(1)(A). The firearm charge arose out of a shootout that occurred when Williams and several coconspirators drove to Penrose Plaza, a shopping mall in South Philadelphia, in search of mеn who had kidnapped the girlfriend and children of one of Williams’ co-conspirators in an attempt to extort cash and cocaine.
The District Court severed the defendants’ cases into several groups and conducted seven separate trials. The jury hung at Williams’ first trial in February 2004, and the Court declared a mistrial. Following a seсond trial in July 2004, Williams was convicted on both counts.
Williams was sentenced in October 2004, after the Supreme Court’s decision in
Blakely v. Washington,
DISCUSSION
I.
Williams argues that the District Court erred in its jury instructions by failing to givе adequate guidance on the concept of multiple conspiracies and on the firearm charge.
1
There is no evidence that Williams objected on this basis at trial, and we therefore review the instructions for plain error.
United States v. Guadalupe,
The District Court read the following instruction on multiple conspiracies to the jury:
*446 Whether there existed a single unlawful agreement, or many such agreements, or indeed no agreement at all, is a question of fact for you, the jury, to determine in accordance with the instructions I’m about to give you. Now, when two or more people join together to further one common unlawful design or purpose, a single conspiracy exists. By way of contrast, multiple conspiracies exist when there are separate unlawful agreements to achieve distinct purposes. Proof of several separate and independent conspiracies is not proof of the single overall conspiracy charged in the indictment unless one of the conspiracies proved happens to be the single overall conspiracy described in the indictment.
Now, you may find that there was a single conspiracy despite the fact that there were changes in either personnel, or activitiеs, or both, so long as you find that some of the coconspirators continued to act for the entire duration of the conspiracy for the purposes charged in the indictment. This is so even if you find that some conspiracy other than the one charged in the indictment existed, even though the purposes of both conspiracies may have been the same and even though there may have been some overlap in membership. Similarly, if you find that the defendant was a member of another conspiracy and not the one charged in the indictment, then you must acquit him.
Williams argues that this instruction was inadequate because the judge also should have told the jury that “even though two individuals may enter into repeated arrangements to sell and buy drugs, it does not necessarily establish a single conspiracy to distribute.” Williams also argues that the evidence suggested two separate charged conspiracies — a conspiracy to distribute drugs and a conspiracy to carry a weapon in response to a kidnapping — and that the District Court therefore should have repeated the instruction on multiple conspiracies in the context of its instructions on the firearm charge.
Williams provides no legal support for these assertions. The District Court explained the difference between a single conspiracy аnd multiple conspiracies in more than enough detail under this Circuit’s case law, and provided all of the information necessary for the jury to understand the relevant concepts.
See, e.g., United States v. Price,
Williams also argues that the District Court’s instructions on the firearm charge were inadequate. He claims that the evidence at trial suggested a lack of nexus between the drug conspiracy and Williams’ use of a firearm, and that the District Court should have stated explicitly that such a nexus was required for conviction on the firearm charge. The judge gave the jury the following instruction, among others, on the firearm charge:
Now, the Government must prove the following elements beyond a reasonable *447 doubt. One, the defendant knowingly committed a drug trafficking crime; two, the defendant knowingly possessed at least one firearm; three, the possession was in furtherance of the drug trafficking crime. Now, the first element that the Government must prove beyond a reasonable doubt is that the defendant committed a drug trafficking crime. The Government alleges that the defendants possessed firearms in furtherance of the conspiracy alleged in count one....
Now, the term in furtherance of, means to advance, move forward, promote, or facilitate the drug trafficking crime. For example, if you determine that based upon the evidence in this case, that the defendant possessеd the firearm and that he did so at least in part to protect his drugs, his drug proceeds, or himself, from competing drug dealers or the police, or that he possessed the firearm for some other reason, which in some way moved forward, advanced, promoted or facilitated the drug trafficking crimes listed in the indictment, then the defendant possessed the firearm in furtherance of a drug trafficking crime. If, however, based upon the evidence in this ease, you find that the defendant did not possess a firearm on or about the date set forth in the indictment or that the firearm was present only for some other purpose, or by mere coincidence, or that the Gоvernment failed to prove this element of the offense beyond a reasonable doubt, then, you must find the defendant not guilty on that count.
This language unambiguously requires the jury to find a nexus between Williams’ possession of a firearm and the charged drug conspiracy, and Williams’ claim is therefore without merit. The prosecution argued at trial thаt the required nexus existed because the kidnapping was perpetrated by individuals knowledgeable about the conspirators’ drug trafficking, and the conspirators’ response to the kidnapping— including the possession of a firearm by Williams — was a response to a threat to the drug conspiracy. Williams was free to dispute this theоry at trial. The District Court properly instructed the jury on the firearm possession charge, and Williams has not established plain error on this point.
II.
Relatedly, Williams argues that the evidence at trial was insufficient as a matter of law to convict him of possession of a weapon in furtherance of a drug trafficking crime under 18 U.S.C. § 924(c). We review this claim for plain error because Williams did not raise the issue in the District Court.
Guadalupe,
The evidence at trial supporting the firearm possession charge was related to the Penrose Plaza incident. Williams asserts that the connection between that incident and the drug conspiracy was too tenuous for the jury to reasonably find that thе gun possession was in furtherance of the conspiracy.
This Court has held that under § 924(c), the government’s evidence “must demonstrate that possession of the firearm advanced or helped forward a drug trafficking crime.”
United States v. Sparrow,
III.
Next, Williams claims that the District Court should have allowed him to cross-examine Courtney Carter, the prosecution’s central witness, about Carter’s assertion on direct examination that he had nevеr committed murder. Williams argues that the prohibition violated his rights under the Sixth Amendment’s Confrontation Clause. We review this claim for abuse of discretion.
United States v. Lore,
Following Carter’s statement on direct examination that he had never committed murder, counsel for Williams told the District Court that he had information indicating that this assertion was false. Specifically, а confidential informant had told a Special Agent of the Bureau for Alcohol, Tobacco, and Firearms that the informant had heard from another person that Carter had once stabbed an individual to death in Philadelphia. The Special Agent was unable to find records of the murder, nor could he find the person who had prоvided this information to the confidential informant. Based on the statement of the confidential informant, Williams’ counsel wished to impeach Carter on cross-examination. The District Court denied the request under Federal Rules of Evidence 608(b) and 403.
Under Rule 608(b), specific instances of conduct of a witness, other than conviction for a crime, may not be proved at trial through extrinsic evidence for the purpose of attacking the witness’s character for truthfulness. The court may at its discretion permit questioning about specific instances of conduct on cross-examination, but only if the conduct is probative of the witness’s character for truthfulness or untruthfulness. Fed.R.Evid. 608(b). Under Rule 403, evidence may be excluded, even if relevant, where “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.” Here, the District Court concluded that the fаct that Carter committed murder was not probative of his truthfulness or untruthfulness under Rule 608(b), and that even if it was, the extreme weakness of the evidence suggesting murder and the potential for an unnecessary mini-trial on the issue indicated that the evidence should be excluded under Rule 403.
We find that the District Court did not abuse its discretion in barring cross-examinatiоn here. A district court “ ‘retains wide latitude insofar as the Confrontation Clause is concerned to impose reasonable limits’ on cross-examination to avoid, among other things, harassment, prejudice, confusion of issues, or interrogation that is only marginally relevant or is repetitive.” Lore,
IV.
Lastly, Williams argues that his case should be remanded for resentencing pursuant to
Booker.
As to the conspiracy conviction, we must remand for resentenc-ing under
Booker,
as the government concedes, because Williams was sentenced under a mandatory Federal Sentencing Guidelines scheme. See
United States v. Davis,
As to the firearm possession conviction, however, the District Court did not apply a sentence under the Sentencing Guidelines, but instead sentenced Williams based on a statutory mandatory minimum under 18 U.S.C. § 924(c)(1)(A). That statute provides for a five-year minimum for possession of a firearm in furtherance of a drug trafficking оffense, which is increased to ten years if the firearm was discharged. Here, the District Court found that a firearm was discharged and sentenced the defendant to the ten-year minimum. The Supreme Court has held that a judge may make findings of facts that increase a defendant’s mandatory minimum sentence as long as those findings do not extend the sentence beyond the maximum authorized by the jury’s verdict.
Harris v. United States,
Harris
remains binding law in the wake of the
Booker
decision.
Booker
did not explicitly overrule
Harris,
and the reasoning in
Booker
does not mandate reversal of
Harris.
In fact, the majority opinion in
Booker
makes no reference to
Harris.
Regardless of whether a Supreme Court decision sheds doubt on an earlier decision of that Court, we may not conclude that the earlier holding has been implicitly overruled. See
United States v. Leahy,
Several other circuits have also affirmed the continuing validity of
Harris
following
Booker. See, e.g., United States v. Estrada,
For the foregoing reasons, we vacate the judgment of sentence as to Count One, for consрiracy to distribute cocaine and cocaine base, and remand for resentencing in accordance with Booker, but we affirm the judgment of sentence as to Count 123, for possession of a firearm in furtherance of a *450 drug trafficking offense. 2 that Williams’ arguments, to the extent not otherwise addressed here, are without merit.
Notes
. The District Court had jurisdiction over this fedеral criminal case pursuant to 18 U.S.C. § 3231. This Court has jurisdiction over Williams’ appeal of his conviction and sentence pursuant to 28 U.S.C. § 1291.
. With permission of this Court, Williams has filed a pro se supplemental brief in this matter. We have considered his claims that the District Court violated his Fourteenth Amendment rights by constructively amending the indictment, and that the District Court lacked jurisdiction to impose the sentence as to the firearm possession conviction. We conclude
