OPINION
Petitioner-Appellant Andre Olden appeals the district court’s denial of his § 2255 motion to vacate his conviction for narcotics distribution. Olden asserts that he was provided ineffective assistance of counsel and completely denied representation by his counsel’s absences at critical stages of his trial. We hold that while Olden cannot establish prejudice to support his ineffective assistance claim, his counsel’s absences at critical stages of his trial completely denied him the representation guaranteed by the Sixth Amendment. However, because we cannot determine whether Olden legitimately waived his right to his own counsel, we remand for an evidentiary hearing on that issue. Accordingly, we VACATE the district court’s denial of Olden’s motion to vacate, and REMAND for further proceedings consistent with this opinion.
I.
Olden was initially indicted on federal conspiracy charges in connection with a drug distribution ring. The original indictment also charged “Carlos LNU” with conspiracy and heroin distribution on March 21, 1990. On February 13, 1992, a grand jury returned a superseding indictment, which continued to charge Olden with conspiracy under Count 1, but made no mention of a “Carlos LNU.”
At trial, the government presented evidence showing that Olden was a drug
*564
“runner,” or distributor, for the leaders of the conspiracy, Karl Wingo and Brett Lang.
See United States v. Lang,
No. 92-2987,
On March 21, 1990, undercover DEA Agent Steven Mitchell, accompanied by Agent Michael Brown, arranged to make a heroin purchase from Wingo. Wingo stated that he would send an unnamed person to meet Mitchell and complete the deal. At the scheduled time, a man walked up to Mitchell’s vehicle and stated he was “one of Karl’s boys.” J.A. at 190. Mitchell asked this individual his name, and he answered “Carlos.” By the way he said his name, Mitchell immediately suspected it was an alias. In any event, Mitchell rejected the drugs offered by “Carlos,” as he suspected the heroin had been “cut,” or diluted through commingling with other substances. After subsequent discussions with Wingo regarding the integrity of the drugs, Mitchell agreed to accept the heroin. A second meeting took place in which Mitchell consummated the deal with the “Carlos” he had initially met.
When Olden appeared for his arraignment in November 1991, Mitchell identified Olden as the “Carlos” who sold him heroin on March 21, 1990. See J.A. at 194-95. In addition, when Olden went to the DEA office to give handwriting samples, Agent Brown positively identified Olden as the “Carlos” who had consummated the March 21 deal. Based on these identifications, all references to “Carlos LNU” were omitted from a later-filed superseding indictment. The superseding indictment, however, did not specifically charge Olden with heroin distribution on March 21; it simply removed the purported charges against “Carlos LNU” in Counts 1 and 4 of the original indictment.
The grand jury transcript indicated that the conduct formerly ascribed to “Carlos” was being imputed to Olden. Additionally, discovery on the day before the trial supplied Olden’s trial counsel, Howard Witten-berg, with Agents Mitchell’s and Brown’s supplemental report implicating Olden as “Carlos.”
Lang,
At trial, in addition to the “Carlos” testimony, the government introduced wiretap testimony in which Karl Wingo discussed efforts by Olden and others to locate various drug paraphernalia before search warrants were executed. Olden responded to the “Carlos” charges by contending that
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the agents testified “Carlos” was fifty to sixty pounds lighter than Olden. The government, however, countered this assertion with testimony from Zajac, who stated that Olden had gained approximately sixty pounds. Additionally, both Agents Mitchell and Brown positively identified Olden as “Carlos” at trial.
See
J.A. at 194, 209-10. Olden was ultimately convicted of the conspiracy charge and sentenced to 165 months. On direct appeal, Olden asserted that the government constructively amended the indictment by charging him with the conduct attributed to “Carlos” and that the district court erred in denying his severance motion.
See Lang,
Olden subsequently filed a § 2255 petition to vacate, asserting ineffective assistance of counsel and that Wittenberg denied him assistance altogether by his several absences during the trial. Olden emphasized Wittenberg’s absences during two particular episodes of the trial when the prosecution introduced evidence allegedly pertaining to Olden’s guilt. On June 5, 1992, Agent Michael Brown, among others, attested to the criminal activities of Olden’s co-defendants, and witness Joanne Person testified that Olden was present at a heroin purchase she made at a local residence. See J.A. at 257. Additionally, on June 15, the government presented wiretap evidence of a conversation between Otis and Karl Wingo, in which Karl asks Otis who is with him, Otis responds that he is with Olden, and the Wingo brothers proceed to have a conversation about illicit activity. See Tr. XVIII at 72. ■
The district court, however, rejected all of Olden’s claims, concluding that he had not established deficient represehtation or prejudice. Regarding Olden’s denial of counsel claim, the district court additionally noted that Olden had consented to Wit-tenberg’s absences. See J.A. at 163-64. With these rulings, the district court denied Olden’s § 2255 motion. Olden now appeals.
II.
Ineffective assistance of counsel claims present mixed questions of law and fact that we review
de novo. See United States v. Jackson,
In assessing counsel’s performance, we inquire whether “counsel’s representation fell below an objective standard of reasonableness,” as measured by “prevailing professional norms.”
Rickman,
*566 Olden contends his counsel was constitutionally deficient for failing to obtain material evidence, failing to file various motions, and excessive absence. He additionally asserts that he was denied Sixth Amendment effective assistance by the aggregate effect of these purported errors. We will discuss each allegation in turn.
A.
Olden first asserts that his trial counsel provided constitutionally deficient representation by failing to learn sooner that the government intended to ascribe the March 21, 1990 criminal conduct of “Carlos” to him. Notwithstanding that the superseding grand jury transcript contained this information, and trial counsel Witten-berg’s admission that he discovered an allegation of Olden as “Carlos” in the grand jury testimony, see J.A. at 307, Wit-tenberg stated that he was “ambush[ed]” at trial by the government’s allegations that Olden was “Carlos.” J.A. at 303. Olden contends that because Wittenberg did not anticipate the “Carlos” allegations, Wittenberg did not pursue, investigate, or develop information that might have exonerated him, including Otis Wingo’s alleged statement that he could identify the true “Carlos.” See Olden’s Br. at 32-33.
While Wittenberg did present a mistaken identity defense, his ability to effectively defend Olden was seriously hampered by his pre-trial unawareness that the government intended to allege that Olden was “Carlos.” As this Court noted on direct appeal, the grand jury transcript and
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pre-trial disclosure — albeit the day before trial — provided notice of the government’s claims on the “Carlos” issue.
See Lang,
Notwithstanding counsel’s provision of ineffective representation, Olden has not established a Sixth Amendment violation on the “Carlos” claim because he cannot establish prejudice. First, it is notable that, outside of the alleged Otis Win-go testimony, Olden has not specifically identified any exculpatory possibilities that were barred by counsel’s belated knowledge of the “Carlos” allegations. Further, both Agents Mitchell and Brown positively identified Olden as “Carlos.” J.A. 194, 209-10. Moreover, Olden was only charged with the Count 1 conspiracy charge, and was not specifically charged with the March 1990 heroin transaction. In addition to the wiretap evidence, the testimony of Michael Zajac and Tirrell Harris as to specific drug transactions consummated by Olden are sufficient to convict him of the conspiracy charge. Accordingly, Olden has not established that his counsel’s deficient representation so compromised the reliability of his conviction that the result of the proceeding would have been different.
See Rickman,
B.
Olden" also contends that his trial counsel was ineffective for failing to file various procedural motions. Specifically, Olden alleges that counsel provided ineffective representation by failing to challenge the indictment, failing to move for a mistrial, *567 and failing to request a special verdict. 1 These claims are without merit.
Olden initially claims that the indictment should have been challenged for variance. Specifically, Olden contends that the jury might have misunderstood the charges it returned against him. This claim fails, however, because the grand jury heard a DEA agent’s testimony that Olden was “Carlos,” and Olden has not established prejudice from any purported variance. Olden also challenges counsel’s representation for failing to move for a mistrial on the government’s purported presentation of “extraneous evidence.” Olden vaguely, and without any citation to the record, contends that the prosecution’s evidence of drug distribution in “other parts of the country and the Phillippines were used” to bolster the conspiracy charge.
See id.
However, this allegation is encompassed within the prior allegations of overbroad admissibility that were dismissed on direct appeal.
See Lang,
Olden additionally contends that his counsel was ineffective for failing to request a special verdict form. Olden asserts that because the conspiracy involved charges of cocaine and heroin distribution, his counsel should have requested a special verdict to determine the respective quantities of heroin and cocaine that supported his conspiracy conviction. However, the statute under which Olden was convicted, 21 U.S.C. § 841(a)(1), provides that it is unlawful to distribute a “controlled substance.” Both heroin and cocaine are proscribed “controlled substances” under § 841(a).
See, e.g., United States v. Jones,
No. 95-1608,
*568 C.
Third, Olden contends that he did not have any representation during those occasions when his counsel was absent from the courtroom and that he did not knowingly and intelligently accept substitute counsel on those occasions. While Sixth Amendment jurisprudence generally requires a claimant to demonstrate deficient representation and prejudice, we presume prejudice when a defendant demonstrates actual conflicts of interest that compromise an attorney’s ability to advocate his client’s interests,
see Rickman,
Nevertheless, representation, or lack thereof, that would otherwise constitute a constitutional violation may be excused when a defendant knowingly and intelligently waives his Sixth Amendment right to counsel.
See United States v. Nichols,
Here, before we consider whether Olden knowingly and intelligently waived his Sixth Amendment rights, we must first consider whether the absences of Olden’s counsel occurred at a sufficiently “critical” stage of the trial to trigger the protections of Cronic. Olden’s counsel, Wittenberg, was absent on numerous occasions during trial. Specifically, on June 5 and June 15, 1992, Wittenberg was absent when the government presented evidence that pertained to Olden’s guilt. On June 5, Agent Brown described the criminal activities of Olden’s co-defendants, and witness Joanne Person testified that Olden was present at a heroin purchase she made at a local residence. See J.A. at 257. In addition, on June 15, the government presented wiretap evidence obtained by Agent Mitchell. This evidence included a conversation between Otis and Karl Wingo in which Otis represented that Olden was with him, and the Wingo brothers proceeded to converse about drug-related activity. See Tr. XVIII at 72. The evidence presented on June 5 and 15, relating to Olden’s presence at drug deals and the Wingo brothers’ apparent comfort in discussing criminal activity around him, tends to implicate Olden in the drug conspiracy of which he was convicted.
When the government presents evidence probative of a defendant’s culpability in criminal activity, or evidence that further implicates a defendant in criminal conduct, that portion of a criminal trial is sufficiently critical to the ultimate question of guilt to trigger the protections of
Cronic. See Green,
We now consider whether Olden waived his Sixth Amendment protections during Wittenberg’s absences on June 5 and 15. On June 4, Wittenberg informed the court *569 that because he had to attend a funeral the next day, he would be absent from the courtroom. The exchange between Olden’s counsel and the court proceeded as follows:
Mr. Wittenberg: My client has no objections to having Timothy Barkovic [Otis Wingo’s counsel] in my absence take notes or whatever. And I would just like to place it on the record at [sic] my client acknowledge that.
The Court: Mr. Olden, is that agreeable with you?
Defendant Olden: Yes.
The Court: All right. Mr. Barkovic, is that agreeable with you?
Mr. Barkovic: Absolutely, your Honor.
The Court: Okay, fine.
J.A. at 252-53. Regarding the second absence, Wittenberg arranged to have co-Defendant Brett Lang’s counsel represent Olden while he was absent. Lang’s counsel explained Olden’s support of his representation as follows:
[Lang’s counsel]: Mr. Wittenberg has called and asked that I again stand in for Mr. Olden. I’ve discussed it with Mr. Olden. [To Olden] You don’t have any objection to me standing in place and stead of Mr. Wittenberg today? Defendant Olden: No.
[Lang’s counsel]: Very good. Thank you.
The Court: Okay. Thanks.
J.A. at 270.
Given the record before us, we cannot determine whether Olden knowingly and intelligently accepted substitute counsel and thereby waived his right to have his own counsel present. The district court did not ascertain whether Olden had any knowledge as to his Sixth Amendment rights, his right to have his own counsel, his right to reject the substitute counsel of his co-defendants, or his right to request a continuance until his own counsel could be present. Nor did the district court engage in the kind of colloquy envisioned by Federal Rule of Criminal Procedure 44(c) when two criminal co-defendants are jointly represented by the same counsel.
See
Fed.R.Crim.P. 44(c). We hold that just as a district court is required to apprise a defendant seeking to represent himself of the nature of his Sixth Amendment rights and the consequences that attend waiver of those rights,
see United States v. Hernandez,
Because the current record does not allow us to determine whether Olden knowingly and intelligently waived his Sixth Amendment rights, we remand for an evidentiary hearing on the extent of Olden’s awareness of his right to have his own counsel present. If Olden can establish that he did not voluntarily, knowingly, and intelligently waive his right to have his counsel present, Olden must be granted a new trial given our conclusion that Wittenberg’s June 5 and 15 absences occurred at critical stages of Olden’s trial. 3
*570 III.
While we reject Olden’s various ineffective assistance claims pertaining to the “Carlos” allegations and his failure to file various procedural motions, we hold that Olden’s counsel was absent at critical stages of the trial, and that if Olden can establish that he did not voluntarily, knowingly, and intelligently waive his right to have his own counsel, he must be granted a new trial. Accordingly, we VACATE the denial of Olden’s § 2255 motion and REMAND for further proceedings consistent with this opinion.
Notes
. Olden additionally claims that Wittenberg should have requested a “lesser included offense” instruction. Olden, however, does not cite any evidence that supports his claim, nor does he attempt to refute substantial evidence showing that he facilitated the distribution activities of Karl Wingo. Accordingly, Olden’s claim is without merit.
. Additionally, Olden attempts to raise issues pertaining to the effectiveness of his counsel at sentencing and on appeal; however these issues were not raised below, and therefore are not cognizable on appeal.
See United States v. Ferguson,
. Olden, also cites Wittenberg’s absences at two Rule 29 hearings and a
Jencks
material hearing. Olden, however, does not aver that these absences occurred at critical stages of his trial, and because he has not shown any prejudice from these absences, we cannot conclude that Wittenberg provided ineffective assistance by missing these hearings. We also note that even though Wittenberg missed one Rule 29 hearing, he nevertheless preserved his right to file a Rule 29 motion. Additionally, we note that the second Rule 29 hearing did not relate to the charges against Olden, and that, with regard to Wittenberg’s absence at the
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hearing, we held on direct appeal that the
Jendcs
materials were not discoverable.
See Lang,
