with whom
Justice Brennan and Justice Marshall join, and, as to Part II, Justice Powell joins, dissenting.In Strickland v. Washington, 466 U. S. 668 (1984), this Court set forth the standards that are to govern a court’s consideration of a criminal defendant’s claims that he has been denied his Sixth Amendment right to effective assistance of counsel. Petitioner Burger presents two such claims in this case. I believe each claim meets those specified standards for establishing a constitutional violation. Each therefore calls for a grant of the federal habeas corpus relief sought by petitioner. Accordingly, I dissent from the Court’s judgment that denies such relief.1
I
A
Petitioner’s first claim rests on his right to conflict-free assistance of counsel. As long ago as Glasser v. United States, 315 U. S. 60 (1942), this Court recognized that such assistance is a component of the Sixth Amendment right to effective assistance of counsel. Id., at 70. This right is so fundamental in our adversarial system of criminal justice that public defender offices in many jurisdictions have rules pre*797eluding representation of more than one of the criminal defendants involved in the same offense.2 Under the Federal Rules of Criminal Procedure3 and under the rules governing professional responsibility,4 consent of a criminal defendant *798is a necessary prerequisite to joint representation, and trial court inquiry into whether the defendant has made a knowing and voluntary waiver of his right to conflict-free representation is strongly encouraged, if not required.5 I do not read *799the majority opinion as departing from the Court’s earlier approval of those practices, see Cuyler v. Sullivan, 446 U. S. 335, 346, nn. 10 and 11 (1980), although I believe that in this case it definitely has misapplied the Sixth Amendment standard that is informed by the rules.
This Court recognizes the unique nature of claims that arise out of a conflict of interest and does not impose on such claims the two-pronged standard of inadequate performance and prejudice, see Strickland v. Washington, 466 U. S., at 687, that applies to general claims of ineffective assistance. Instead, prejudice is presumed if a defendant demonstrates that his attorney “ ‘actively represented conflicting interests’ and that ‘an actual conflict of interest adversely affected his lawyer’s performance.’” Id., at 692, quoting Cuyler v. Sullivan, 446 U. S., at 350, 348.6
*800The presumption of prejudice in cases presenting a conflict of interest that adversely affected counsel’s performance is warranted because the duty of loyalty to a client is “perhaps the most basic” responsibility of counsel and “it is difficult to measure the precise effect on the defense of representation corrupted by conflicting interests.” Strickland v. Washington, 466 U. S., at 692. This difficulty in assessing prejudice resulting from a conflict of interest is due in part to the fact that the conflict may affect almost any aspect of the lawyer’s preparation and presentation of the case. Because the conflict primarily compels the lawyer not to pursue certain arguments or take certain actions, it is all the more difficult to discern its effect. See Holloway v. Arkansas, 435 U. S. 475, 490 (1978) (“[I]n a case of joint representation of conflicting interests the evil ... is in what the advocate finds himself compelled to refrain from doing, not only at trial but also as to possible pretrial plea negotiations and in the sentencing process” (emphasis in original)). The presumption of prejudice in conflict-of-interest cases is particularly appropriate because lawyers are charged with the knowledge that they are obliged to avoid such conflict. See n. 4, supra. A judge can avoid the problem by questioning the defendant, at an early stage of the criminal process, in any case presenting a situation that may give rise to conflict, in order to determine whether the defendant is aware of the possible conflict and whether he has waived his right to conflict-free representation.
B
Although the Court purports to apply this conflict-of-interest ineffectiveness standard in the present case, see ante, at *801783, I cannot agree with its conclusions. Contrary to the Court’s reasoning, there simply can be no doubt that petitioner’s court-appointed attorney actively represented conflicting interests through his role in the defenses of petitioner and his coindictee, Thomas Stevens. Defense counsel was appointed to represent petitioner, and his partner in their two-partner law firm was appointed to represent Stevens. App. 30-31. The two lawyers interviewed both defendants “from the beginning” and assisted in the preparation of both cases. Id., at 32. The partner “sat in” with counsel at petitioner’s trial and “helped” him. Id., at 35. Apparently, others viewed the two lawyers as joint counsel for petitioner at his first trial inasmuch as the prosecutor directed the attention of the prospective jurors during voir dire to both lawyers and asked the jurors whether they ever had been represented by either of them. First Tr. 28, 37, 42, 48.7 The partner is listed as appearing for petitioner Burger in the transcript of that trial. Id., at 1. While there is no record evidence that petitioner’s counsel assisted during Stevens’ trial, counsel conceded that, in addition to his assistance in pretrial research, strategy, and interviews of Stevens, he prepared the appellate briefs for both petitioner and Stevens after the second sentencing proceedings. App. 54. See Burger v. Kemp, 753 F. 2d 930, 941 (CA11 1985) (District Court opinion, adopted by Court of Appeals as its own, noting that “it may be said that the two attorneys at times acted as one while each prepared for trial and appeal”). The facts therefore demonstrate that the two lawyer-partners actively represented both petitioner and Stevens.
This active representation of the two coindictees by petitioner’s counsel constituted representation of actual conflict*802ing interests.8 Petitioner’s and Stevens’ interests were diametrically opposed on the issue that counsel considered to be crucial to the outcome of petitioner’s case — the comparative culpability of petitioner and Stevens. Petitioner confessed to participation in the crime but placed the primary blame on Stevens. Second Tr. 278. In his confession, petitioner stated that he thought they simply would abandon the taxicab. Ibid. Botsford, who had been with petitioner and Stevens in the taxicab for a while, corroborated petitioner’s statement in his testimony at both petitioner’s and Stevens’ trials. When questioned about what petitioner and Stevens had told him they were going to do with the taxicab and its driver, Botsford replied:
“Well, Tom Stevens said that he thought they should kill him. And, I told him L thought he was crazy. And, Burger didn’t like the idea of killing him either. Burger said that they ought to let him go, that they ought to drive off in the woods somewhere and let him out, and then take the car somewhere and put it like, I think somebody mentioned the ocean.” Id., at 112-113; see also First Tr. 100, 111 (Botsford agreeing that petitioner “was just sorta going along, sorta doing sorta like Stevens was telling him to do”).
Petitioner stated that after he had checked to see if the driver was all right, Stevens returned to where they had stopped the taxicab and told petitioner to drive the car into the pond. Second Tr. 278. Stevens also confessed, but in *803doing so he pointed to petitioner as the more culpable. See Stevens v. State, 242 Ga. 34, 35, 247 S. E. 2d 838, 840 (1978). Stevens stated in his confession that he had not wanted to kill the taxicab driver and had not known that petitioner was planning to drive the automobile into the pond. Ibid. Stevens’ attempt to argue his lesser culpability was his “sole mitigatory defense” at his second sentencing trial. See Stevens v. State, 245 Ga. 583, 585, 266 S. E. 2d 194, 197, cert. denied, 449 U. S. 891 (1980).
The Court disregards this direct conflict between petitioner’s and Stevens’ respective interests and, instead, attempts to minimize the active representation of both defendants by the two lawyer-partners. The Court opines that the “overlap of counsel” did not constitute an “active representation of competing interests” by petitioner’s counsel. Ante, at 783. The Court supports this assertion by blandly relying on its perception of a shortage of lawyers to handle these cases, on its view of the benefits that defendants may derive from joint representation when there is a common defense, and on the assumption that lawyers are aware of their duty of loyalty to clients. Ante, at 783-784. The Court, however, does not identify any record evidence indicating that there were no other lawyers available for appointment. In addition, the other factors are of questionable relevance in this case which did not involve a common defense for the two coindictees and in which counsel did not even consider that a conflict of interest might exist.
The Court also points to the fact that petitioner and Stevens were tried separately and relies on the observation in Cuyler v. Sullivan, 446 U. S., at 347, that separate trials in that case had “reduced the potential for a divergence in [the defendants’] interests.” Ante, at 784. The separate trials in this case, however, did absolutely nothing to reduce the potential for divergence of interests at the two critical stages that petitioner argues were adversely affected by the *804conflict of interest, that is, pretrial plea negotiations and post-trial appeal.9
The Court’s further attempt to disavow the existence of an actual conflict of interest by suggesting strategic reasons for the actions taken by petitioner’s counsel on appeal and in pretrial negotiations is, with all respect, not supported by the record. The Court’s suggestion that counsel’s failure to make a “lesser culpability” argument on appeal was the result of a sound strategic conclusion that the claim was weak, ante, at 784, is sheer speculation. As demonstrated by petitioner’s confession and Botsford’s testimony, the leaser culpability argument certainly did not lack an evidentiary foundation. This speculation that counsel dropped the claim after trial because it was a weak argument for appeal is counterintuitive. The lesser culpability argument would *805have been stronger on appeal than at trial. On appeal, the reviewing court had both cases before it at the same time and thus was in the actual position of being able to compare the cases at the time it reviewed the appropriateness of the sentences imposed.
Moreover, the speculation that counsel dropped the argument on appeal because of its weakness ignores the fact that comparative culpability is directly relevant to the statutorily mandated appellate review of capital cases in Georgia. The State’s statute specifies that the Georgia Supreme Court’s review of capital cases is to include consideration “[w]hether the sentence of death is excessive or disproportionate to the penalty imposed in similar cases, considering both the crime and the defendant.” Ga. Code Ann. § 17—10—35(c)(3) (1982) (emphasis added). The evidence and argument presented at trial concerning petitioner’s role as a follower of Stevens’ directions and petitioner’s lesser involvement in the assaultive behavior prior to the murder would clearly be relevant on appeal under the terms of the statute. Hence, even if counsel did base his decision on the “strategic” reason suggested by the Court,10 that decision was based on an errone*806ous view of the law and thus could not be reasonable.11 See Kimmelman v. Morrison, 477 U. S. 365, 385 (1986) (counsel’s judgment found to be contrary to prevailing professional norms because justifications offered by counsel reflected ignorance of the law or attempt to shift blame for inadequate preparation).
Setting aside the speculation as to counsel’s motive, it becomes clear that his joint representation of petitioner and Stevens precluded him, as a matter of professional responsibility, from pursuing the lesser culpability argument in petitioner’s appellate brief. It would have been inconsistent with his duty of loyalty to Stevens to argue that the Georgia Supreme Court should reduce petitioner’s sentence to life imprisonment because Stevens was the more culpable defendant who deserved the death sentence for this heinous murder.
It is difficult to imagine a more direct conflict than existed here, where counsel was preparing the appellate brief for petitioner at the same time that he was preparing the appellate brief for Stevens, and where the state statute specifies that one of the roles of that appellate process is to consider the comparative culpability and sentences of defendants involved in similar crimes. Counsel’s abandonment of the *807lesser culpability argument on appeal, the stage at which the two cases would be reviewed contemporaneously, is indicative of the “ ‘struggle to serve two masters.’” See Holloway v. Arkansas, 435 U. S., at 482, quoting Glasser v. United States, 315 U. S., at 75. This record compels a finding that counsel’s representation of the conflicting interests of petitioner and Stevens had an adverse effect on his performance as petitioner’s counsel.
Defense counsel’s representation of conflicting interests also placed him in an untenable position at an earlier stage of the proceedings — during pretrial plea bargaining. The two partners helped each other during that period with their two cases and, as part of the pretrial preparation, petitioner’s counsel talked with both petitioner and Stevens “from the beginning.” App. 32. Counsel was not in a position to negotiate with the prosecution to the detriment of Stevens. Although he asserted that he continually attempted to negotiate with the prosecutor on behalf of petitioner for a sentence of life imprisonment, he conceded that he never offered the prosecutor petitioner’s testimony against Stevens. Id., at 52, 74-75. Certainly, counsel was not reasonable in expecting a plea bargain if he was not offering the prosecutor the most significant bargaining chip he possessed — petitioner’s testimony against Stevens.12
*808c
I also disagree with the Court’s rejection of petitioner’s argument that the actual conflict of interest was aggravated by the widespread knowledge of the cases in the small area from which the jury was drawn. Ante, at 787-788. Juror knowledge that the two cases were being tried by local law part*809ners on inconsistent theories could create a conflict of interest because, in order to preserve the credibility of their argument in either case, the lawyers would have to deny the validity of their contradictory approach in the other. A crucial feature in any case is the credibility of a defendant’s lawyer in the minds of the jury.
The Court’s observation that “the community would have had the same awareness that the theories were inherently inconsistent” if two unaffiliated lawyers had advanced the inconsistent defenses, ante, at 788, may well be true, but it says nothing of the difference that awáreness could make in the community’s view of the cooperating lawyer-partners’ credibility. The Court fails to recognize that, although the credibility of two unaffiliated attorneys presenting inconsistent arguments would not be questioned, the credibility of two local law partners assisting each other in the two cases could well be questioned if it was known that the lawyers working together presented inconsistent theories in the separate cases. Obviously, a jury might suspect that, in one of the cases, the lawyers were pressing an argument they did not believe to be true.
The adverse effect of this conflict on credibility would have been magnified when petitioner’s and Stevens’ cases were remanded for the second sentencing proceeding and the blame-shifting arguments were repeated. By the time of the second sentencing hearing, the verdicts in the original trials and sentencing proceedings had become known to the community.13 Where, as here, the community was aware that *810the same law partners together were representing two defendants in capital cases and that they were arguing inconsistent theories that placed the blame on that defendant who did not happen to be on trial at the moment, the lawyers’ credibility and their effectiveness as counsel were significantly undermined.
D
Finally, I conclude that the trial court in this case erred in failing to inquire into whether petitioner knowingly and voluntarily had waived his constitutional right to conflict-free representation. When this Court, in its opinion in Cuyler v. Sullivan, addressed the question of the state trial court’s duty to make such an inquiry, it specified: “Unless the trial court knows or reasonably should know that a particular conflict exists, the court need not initiate an inquiry.” 446 U. S., at 347 (emphasis added). Here, the trial judge, who appointed the two defense counsel and who presided over both petitioner’s trial and Stevens’ trial, should have known of the conflict from the outset inasmuch as the two confessions, given before the two partners were appointed, were in direct conflict on the question as to which defendant was the prime architect of the crime. In any event, by the time the appeal was taken, the trial court, undoubtedly familiar with the role that comparative culpability plays in appellate review of capital cases under the Georgia statute, was well aware that the primary defense of each defendant against the death sentence was that the other was more culpable. It therefore was the court’s obligation to inquire whether petitioner had consented to the joint representation with the knowledge of the possible conflicts of interests. See Glasser v. United States, 315 U. S., at 71 (“The trial court should protect the right of an accused to have the assistance of coun*811sel”). The court could not properly rely on an assumption that petitioner had given knowing and voluntary consent once the judge became aware of the actual conflict, particularly where he was made aware during the suppression hearing that petitioner was a 17-year-old at the time of the appointment of counsel, had an IQ of 82, functioned at the level of a 12-year-old, and was diagnosed as having psychological problems. First Tr. 244, 245, 247-248.
II
Even if no conflict of interest existed in this case, I would still dissent from the Court’s denial of relief because petitioner was deprived of the effective assistance of counsel in connection with his capital-sentencing proceeding. His counsel failed to investigate mitigating evidence and failed to present any evidence at the sentencing hearing despite the fact that petitioner was an adolescent with psychological problems and apparent diminished mental capabilities. I agree with the Court that the adversarial nature of Georgia’s capital-sentencing proceedings is sufficiently similar to a trial that petitioner’s claim is governed by the same standards that apply to general claims of ineffective assistance of counsel at trial. Ante, at 788; see Strickland v. Washington, 466 U. S., at 686-687. It is also important to “keep in mind that counsel’s function, as elaborated in prevailing professional norms, is to make the adversarial testing process work in the particular case.” Id., at 690. Applying that standard to petitioner’s claim in light of the record of this case yields a finding that the inaction by petitioner’s lawyer was “outside the wide range of professionally competent assistance” and was prejudicial to petitioner. Id., at 690, 692.
In Strickland, this Court specifically addressed counsel’s duty to investigate. It explained:
“[Strategic choices made after thorough investigation of law and facts relevant to plausible options are virtually unchallengeable; and strategic choices made after *812less than complete investigation are reasonable precisely to the extent that reasonable professional judgments support the limitations on investigation. In other words, counsel has a duty to make reasonable investigations or to make a reasonable decision that makes particular investigations unnecessary. In any ineffectiveness case, a particular decision not to investigate must be directly assessed for reasonableness in all the circumstances, applying a heavy measure of deference to counsel’s judgments.” Id., at 690-691.
See also Kimmelman v. Morrison, 477 U. S. 365 (1986). The limitation counsel placed on his investigation of the evidence of petitioner’s mental capabilities and psychological makeup despite the indications that petitioner had problems in these respects was not supported by reasonable professional judgment.
Counsel stated that he based his decision not to move the court for a complete psychological examination of petitioner on his prior experience with the mental hospital where, he assumed, petitioner would be sent for the examination. App. 62-63. He stated that “the results I’ve had with personnel at Central Hospital as far as the defense is concerned . . . hasn’t been good at all.” Id., at 63. He added that he thought that any further examinations would yield the same psychopathic diagnosis reached by the psychologist who had examined petitioner once briefly and primarily to administer an IQ test for purposes of the hearing on whether petitioner’s confession was admissible. Ibid.
Counsel’s failure to request an examination because of what he considered to- be a biased procedure constituted a breakdown in the adversarial process. If in fact the procedure for psychological examinations of an indigent criminal defendant in that jurisdiction was biased, the role of petitioner’s counsel at least was to seek an alternative examination process or to challenge the biased procedure. Counsel’s decision to forgo the psychological examination imperiled *813petitioner’s ability to counter the prosecutor’s argument that he deserved to be executed for his role in the murder and therefore undermined the reliability of the sentencing proceeding. Moreover, such a decision to proceed without the examination in a case in which an adolescent with indications of significant psychological problems and diminished mental capabilities faces the death penalty is contrary to professional norms of competent assistance. The usefulness of a thorough evaluation in a case where there are indications that the capital defendant has problems of that kind is obvious. See Eddings v. Oklahoma, 455 U. S. 104, 116 (1982); cf. Ake v. Oklahoma, 470 U. S. 68 (1985).
Counsel’s decision not to investigate petitioner’s family or childhood background also was not within the range of professionally reasonable judgment. Viewed as of the. time he decided not to get in touch with any family member or to investigate any place where petitioner had lived, counsel provided inadequate assistance. He relied on petitioner to suggest possible witnesses or mitigating evidence. But his question to petitioner whether he could produce evidence of “anything good about him,” App. 51, hardly could be expected to yield information about petitioner’s childhood and broken home. It is unlikely that in response to that question a defendant would volunteer the facts that his father threw him out of the house, that his mother did the same, that his stepfathers beat him and his mother, or that one stepfather involved him in drugs and alcohol at age 11. All this is mitigating evidence that could be highly relevant. See Eddings v. Oklahoma, 455 U. S., at 107. Furthermore, counsel testified that he spoke with petitioner perhaps “half a dozen times,” the longest being “[pjrobably about an hour.” App. 51. These bare six hours provided counsel little time to discuss possible mitigating evidence for the sentencing proceeding because counsel surely also had to discuss in detail the circumstances surrounding petitioner’s confession which he was challenging and all the other features of the *814guilt/innocence phase of the trial. Moreover, after petitioner’s death sentence was vacated on appeal and the case was remanded, counsel did not perform any further investigation whatsoever during the 9-month period before the second hearing. He simply proceeded in the same manner that had resulted in petitioner’s being sentenced to death at the first hearing. Id., at 71.
The only reason counsel spoke to petitioner’s mother at all was because she sought him out after learning elsewhere that her son was charged with murder. Id., at 83. Even after petitioner’s mother initiated the contact, counsel’s conduct was inexplicable. He testified that he never explained the penalty phase of the trial to petitioner’s mother or what evidence then could be presented. Id., at 50. The Court finds reasonable counsel’s decision not to have petitioner’s mother testify because he concluded that her testimony might be counterproductive in that it might reveal a petty offense petitioner had committed. Ante, at 792. That decision is a prime example, however, of a strategic choice made after less-than-adequate investigation, which therefore is not supported by informed professional judgment. Counsel could not reasonably determine whether presenting character witnesses would pose a risk of disclosing past criminal behavior by petitioner without first determining whether there was any such criminal behavior. Although there is a reference in the record to an incident of shoplifting a candy bar, App. 90-91, and another reference to an automobile accident, id., at 92-93, there is no indication that counsel ever determined whether petitioner in fact had a prior criminal record. The account provided by petitioner’s mother of petitioner’s hitchhiking to Florida to be with her after having been thrown out of his father’s house and having to sell his shoes during the trip to get food, id., at 92, may well have outweighed the relevance of any earlier petty theft.
I also find troubling the fact that defense counsel rejected the assistance of another lawyer (who had known petitioner) *815merely on the basis that the lawyer was black. Id., at 57-58. The lawyer offered to come to Georgia at his own expense to provide what assistance he could. Id., at 86. Counsel thought his assistance might have “an ill effect,” however, on the trial of petitioner who is white. Counsel testified that he and the lawyer agreed that because of his race it was not wise to have the lawyer testify. Id., at 58. I question whether this is a reasonable professional decision. The adversarial duty of petitioner’s counsel was to pursue a means by which to present testimony from such a witness while doing his best to safeguard the trial from racial prejudice. See, e. g., Turner v. Murray, 476 U. S. 28 (1986). Counsel apparently made no effort to investigate possible racial bias of petitioner’s jury. App. 58-59. Like counsel’s abandonment of the psychological investigation because of the suspected unfairness of the examination procedure, his surrender to the perceived risk of racial discrimination without any effort to eliminate that risk is inconsistent with his adversarial role and his responsibility to further the reliability of the court proceeding.
Acceptance of the unpleasant likelihood of racial prejudice in such a trial, however, does not justify counsel’s failure to accept assistance from the lawyer in any number of ways, such as investigating petitioner’s childhood background in Indianapolis where the lawyer had known petitioner. Testimony by petitioner’s mother at the federal habeas corpus hearing revealed that when the lawyer was in law school he had worked in a volunteer “big brother” organization for men who spent time with children who did not have a father-son relationship or a big brother. Id., at 85. He was undoubtedly familiar with some of petitioner’s friends and family members there. The affidavits submitted at the federal hearing, 1 Record 139-157, indicate that many of those persons still reside in Indianapolis but were never approached by counsel. In sum, I reluctantly conclude that counsel fell short in his “duty to make reasonable investigations or to *816make a reasonable decision that makes particular investigations unnecessary.” Strickland v. Washington, 466 U. S., at 691. Application of the Strickland standard to this case convinces me that further investigation was compelled constitutionally because there was inadequate information on which a reasonable professional judgment to limit the investigation could have been made.14
Having concluded that the conduct of petitioner’s lawyer in failing to pursue an investigation into petitioner’s psychological problems or into his family and childhood background was professionally unreasonable, given the circumstances known to counsel at the time, I must also address the question whether this inadequate performance prejudiced petitioner. In my view, if more information about this adolescent’s psychological problems, troubled childhood, and unfortunate family history had been available, “there is a reasonable probability that . . . the sentencer — including an appellate court, to the extent it independently re weighs the evidence — would have concluded that the balance of aggravating and mitigating circumstances did not warrant death.” Strickland v. Washington, 466 U. S., at 695.
I cannot refrain from remarking on the similarities between the evidence of petitioner’s childhood and that presented in Eddings v. Oklahoma, 455 U. S., at 107. Recognizing there the force of such evidence in a decision whether an individual should be sentenced to die, this Court held that the death sentence had to be vacated and the case remanded for another sentencing proceeding where the sentencing authority would consider the mitigating evidence. Id., at 115-117. Because the decision not to present such *817evidence to the sentencing authority in petitioner’s case was not supported by reasonable professional judgments, the reliability of the capital-sentencing proceeding was undermined. But for defense counsel’s disinterest in developing any mitigating evidence to permit an informed decision, there is a reasonable possibility that the outcome of the sentencing hearing would have been different. Counsel’s conduct “so undermined the proper functioning of the adversarial process” that the sentencing hearing cannot “be relied on as having produced a just result.” Strickland v. Washington, 466 U. S., at 686.
Ill
Petitioner was denied the effective assistance of counsel guaranteed by the Sixth Amendment due to his trial counsel’s active representation of the conflicting interests of his coindictee. Given the indications of petitioner’s psychological problems and diminished mental capabilities known to petitioner’s lawyer, counsel’s failure to perform an investigation into those problems and into petitioner’s background denied petitioner effective assistance of counsel at his capital-sentencing hearing. Petitioner is entitled to a new trial with conflict-free representation by counsel and to a new capital-sentencing hearing with effective assistance of counsel. I respectfully dissent from this Court’s judgment denying relief.
I agree with the Court’s conclusion, ante, at 782, n. 5, that the Court of Appeals should be affirmed to the extent it held that any impermissible effect of the jury instruction on malice given at the guilt/innoeence phase of trial was harmless beyond a reasonable doubt. See 785 F. 2d 890 (CA11), clarified, 796 F. 2d 1313 (1986). I also agree with the Court’s observation, ante, at 779, n. 1, that petitioner has not advanced here the question of the constitutionality of executing a person for a murder committed while he was a minor, and thus there is no need to address the merits of that issue or the availability of the claim to petitioner in a future proceeding.
In Cuyler v. Sullivan, 446 U. S. 335 (1980), this Court noted that the vast majority of public defender offices have a strong policy against multiple representation and that approximately half never undertake such representation. Id., at 346, n. 11; see also Lowenthal, Joint Representation in Criminal Cases: A Critical Appraisal, 64 Va. L. Rev. 939, 950, and n. 40 (1978). We further observed in Cuyler that the private bar may be less aware of conflicts of interests in such instances. 446 U. S., at 346, n. 11. This observation certainly is supported by the testimony of petitioner’s attorney in this case that he never even considered that a conflict might arise out of the representation of two defendants facing the death penalty for the commission of the same murder. See App. 32-34.
Criminal Rule 44(c) provides in relevant part:
‘Whenever two or more defendants have been jointly charged . . . and are represented by . . . retained or assigned counsel who are associated in the practice of law, the court shall promptly inquire with respect to such joint representation and shall personally advise each defendant of his right to the effective assistance of counsel, including separate representation.”
Ethical Canon 5-16 of the ABA Code of Professional Responsibility states:
“In those instances in which a lawyer is justified in representing two or more clients having differing interests, it is nevertheless essential that each client be given the opportunity to evaluate his need for representation free of any potential conflict and to obtain other counsel if he so desires. Thus, before a lawyer may represent multiple clients, he should explain fully to each client the implications of the common representation and should accept or continue employment only if the clients consent.”
Disciplinary Rule 5-105(D) states:
“If a lawyer is required to decline employment or to withdraw from employment under a Disciplinary Rule, no partner, or associate, or any other lawyer affiliated with him or his firm, may accept or continue such employment.” See also ABA Model Rules of Professional Conduct 1.7 and 1.10(a) (1984). The American Bar Association, in its Standards for Criminal Justice, explains:
“Except for preliminary matters such as initial hearings or applications for bail, a lawyer or lawyers who are associated in practice should not undertake to defend more than one defendant in the same criminal ease if the *798duty to one of the defendants may conflict with the duty to another. The potential for conflict of interest in representing multiple defendants is so grave that ordinarily a lawyer should decline to act for more than one of several codefendants except in unusual situations when, after careful investigation, it is clear that:
“(i) no conflict is likely to develop;
“(ii) the several defendants give an informed consent to such multiple representation;
“(in) the consent of the defendants is made a matter of judicial record.
“In determining the presence of consent by the defendants, the trial judge should make appropriate inquiries respecting actual or potential conflicts of interest of counsel and whether the defendants fully comprehend the difficulties that an attorney sometimes encounters in defending multiple clients.
“In some instances, accepting or continuing employment by more than one defendant in the same criminal ease is unprofessional conduct.” ABA Standards for Criminal Justice 4-3.5(b) (2d ed. 1979) (emphases in original).
In Strickland v. Washington, 466 U. S. 668 (1984), this Court stated that the Sixth Amendment relies upon the “legal profession’s maintenance of standards sufficient to justify the law’s presumption that counsel will fulfill the role in the adversary process that the Amendment envisions.” Id., at 688. Where, as here, the legal profession’s standards were not followed, no such presumption is appropriate.
Subsequent to petitioner’s trial, the Georgia Supreme Court, exercising its supervisory authority, adopted a rule that in capital cases codefendants must be provided with separate and independent counsel. Fleming v. State, 246 Ga. 90, 270 S. E. 2d 185, cert. denied, 449 U. S. 904 (1980). The court cited the provision in the Code of Professional Responsibility that requires that any lawyer affiliated in a firm with a lawyer who is disqualified must also be disqualified, and thereby indicated that the rule applies to representation by a single attorney or by members of the same firm. 246 Ga., at 93, n. 7, 270 S. E. 2d, at 188, n. 7. The court explained that a rule of separate and independent representation “is especially necessary where the death penalty is sought, because in these cases even a slight conflict, irrelevant to guilt or innocence, may be important in the sentencing phase.” Id., at 93, 270 S. E. 2d, at 188; see also id., at 95, 270 S. E. 2d, at 189 (Bowles, J., concurring) (“No two defendants share *799equal responsibility for a crime. Usually one is more culpable than the other or for any number of reasons has a greater degree of responsibility for what occurred. One may also be more entitled to leniency based on such factors as age, intelligence, motive, background, previous conduct or record, etc. Common counsel eliminates any practical possibility of plea bargaining”). But see id., at 95, 97, 270 S. E. 2d, at 189, 191 (Hill, J., concurring specially) (cautioning that although presumption against joint representation is appropriate, a per se rule against joint representation may not be because capital defendants should be able to waive right to conflict-free representation if it would be to their benefit); id., at 98, 270 S. E. 2d, at 191 (Jordan, P. J., dissenting) (arguing that defendant in that ease should be permitted opportunity to make informed and voluntary waiver of right to conflict-free representation).
What happened in petitioner’s case is therefore unlikely to be repeated in Georgia.
The distinction between a prejudice showing and a showing of adverse effect on an attorney’s performance apparently has been difficult for some courts to discern. See generally Note, Conflicts of Interest in the Representation of Multiple Criminal Defendants: Clarifying Cuyler v. Sullivan, 70 Geo. L. J. 1527, 1536-1561 (1982). The Court’s decision in Strickland v. Washington, made clear, however, that demonstrating that a conflict adversely affected counsel’s performance does not equate with the standard applied to general ineffectiveness claims that requires a showing that “there is a reasonable probability that, but for counsel’s unpro*800fessional errors, the result of the proceeding would have been different.” 466 U. S., at 694. The adverse-effect standard is necessary in conflict-of-interest cases to trigger the presumption of prejudice because such a presumption in these cases is of a more limited nature than the automatic presumption of prejudice that arises in cases of actual or constructive denial of the assistance of counsel altogether and cases of state interference with assistance of counsel. Id., at 692.
The transcripts of petitioner’s first trial, including his first sentencing hearing, and of his second sentencing hearing were submitted as Exhibit A and Exhibit C, respectively, to respondent’s answer to petitioner’s federal habeas corpus petition in District Court. See 1 Record, pleading 11. Citations to the transcript of the first trial and hearing are designated “First Tr.” and citations to the second hearing are designated as “Second Tr.”
The great degree of deference the Court accords the lower courts’ conclusions on this matter, ante, at 784-785, and its emphasis on the “heavily fact-based rulings,” ante, at 785, appear misplaced in the analysis of this ease. The question of multiple representation “is a mixed determination of law and fact that requires the application of legal principles to the historical facts,” Cuyler v. Sullivan, 446 U. S., at 342, as are the general ineffectiveness question and the “performance and prejudice components of the ineffectiveness inquiry.” Strickland v. Washington, 466 U. S., at 698.
The fact that defendants are given separate trials may eliminate some problems created by a conflict of interest, but severance does not alleviate numerous other dilemmas faced by lawyers representing two or more defendants charged and indicted together. See Developments in the Law, Conflicts of Interest in the Legal Profession, 94 Harv. L. Rev. 1244, 1380 (1981); Geer, Representation of Multiple Criminal Defendants: Conflicts of Interest and the Professional Responsibilities of the Defense Attorney, 62 Minn. L. Rev. 119, 143-144 (1978). The right to conflict-free representation by counsel in pretrial and appellate proceedings of criminal cases may be as significant as such representation at trial. Id., at 125-127. In an earlier discussion of the hazards of an attorney’s representing more than one coindietee, the Court described the very conflicts that present themselves in this case:
“Joint representation of conflicting interests is suspect because of what it tends to prevent the attorney from doing. For example, in this case it may well have precluded defense counsel. . . from exploring possible plea negotiations and the possibility of an agreement to testify for the prosecution, provided a lesser charge or a favorable sentencing recommendation would be acceptable. Generally speaking, a conflict may also prevent an attorney from challenging the admission of evidence prejudicial to one client but perhaps favorable to another, or from arguing at the sentencing hearing the relative involvement and culpability of his clients in order to minimize the culpability of one by emphasizing that of another.” Holloway v. Arkansas, 435 U. S. 475, 489 (1978).
Contrary to the Court’s speculation, counsel himself did not claim to have dropped the lesser culpability argument because of its weakness. Rather, he stated that he did not raise the issue of the difference in the culpability of the two eoindictees in petitioner’s appellate brief because, although he thought it was the key issue at trial, App. 64, he thought “that was a jury decision based on the evidence,” id., at 53, and that the only way he could see to raise the issue was on the theory of “lack of evidence to sustain the finding of the jury as to the — what punishment to give.” Id., at 54. This basis for the action certainly cannot be considered strategically sound because it reflects an erroneous legal interpretation of appellate review in capital cases in Georgia. By failing to argue on petitioner’s behalf that he was less culpable than Stevens, counsel diminished the reliability of the Georgia Supreme Court’s proportionality review in this case. This Court has held that proportionality review is an important component of the Georgia capital-sentencing system. See Gregg v. Georgia, 428 U. S. 153, 198, 204-206 (1976) (opinion of Stewart, Powell, and Stevens, JJ.). Therefore, even if counsel’s assistance on appeal had not been hindered by *806an actual conflict of interest, one may well question whether his conduct in this regard met the minimal level of professional reasonableness.
Counsel’s self-serving declarations that he did not permit his representation of Stevens to affect his representation of petitioner cannot outweigh the conflict revealed by the record itself. Counsel is not a fully disinterested party to this proceeding due to the collateral consequences that could result from a determination that he rendered ineffective assistance of counsel. He certainly has an interest in disavowing any conflict of interest so that he may receive other court appointments that are a source of clients for the criminal defense work of the partners’ practice. App. 44. The approximate $9,000 fee that counsel received in this case for his representation of petitioner was the largest the firm had ever received for a criminal case. Ibid. This payment, along with the payment received by the partner for his court appointment in the Stevens case, went into their firm account. Id., at 31.
The Court discounts counsel’s failure to offer the prosecutor petitioner’s testimony against Stevens by stating that there is no indication that the prosecutor would have been receptive to the offer. Ante, at 785-786. The Court focuses on the strength of the evidence of petitioner’s and Stevens’ guilt and concludes that there is no reason to doubt that the prosecutor refused to discuss the matter prior to the first trial and insisted on seeking the death penalty after the remand of the case. Ante, at 786. This reasoning, however, misses the point of petitioner’s argument. The question is whether the prosecutor would have insisted on seeking the death penalty against petitioner if counsel had attempted to persuade him otherwise by offering him petitioner’s testimony against Stevens.
Although it is easy to assume that the prosecutor would not have indulged in plea bargaining in this case because of the significant evidence of *808guilt, that approach ignores the reality of bargaining in capital cases. The evidence of guilt is not the only factor prosecutors consider. Rather, the relevant factors include the aggravating and mitigating circumstances surrounding the case as well as practical considerations such as the cost of pursuing the death penalty. See Gross & Mauro, Patterns of Death, 37 Stan. L. Rev. 27, 106-107 (1984) (“Since death penalty prosecutions require large allocations of scarce prosecutorial resources, prosecutors must choose a small number of cases to receive this expensive treatment”). Such practical considerations might weigh even more heavily prior to a second capital-sentencing trial on remand from the state appellate court’s reversal of the first death sentence. Furthermore, there may be collateral evidentiary considerations during the pretrial phase that warrant a plea to life imprisonment for one coindictee in exchange for evidence that will strengthen the other case. For example, in this ease, if the prosecutor had thought that there was a likelihood that petitioner’s counsel might prevail on his argument that petitioner’s confession should be suppressed, and if petitioner’s counsel had offered petitioner’s testimony against Stevens, the prosecutor might have decided that rather than risk the possibility of his case against petitioner being destroyed by suppression of his confession, he would permit petitioner to plead to a life sentence in exchange for his testimony against Stevens and pursue the death sentence against Stevens.
Petitioner’s attorney had the duty to serve his role in the adversary system and make an offer on petitioner’s behalf to testify against Stevens if petitioner was willing to do so, and thereby avoid the possibility of being executed. Petitioner’s burden of showing that the conflict of interest adversely affected his counsel’s performance therefore was met. The Court’s suggestion that whether the prosecutor would have accepted such an offer is the determinative factor verges on requiring a showing of prejudice which, of course, is inappropriate in the context of petitioner’s conflict-of-interest claim. See n. 6, supra. Counsel’s complete failure to offer petitioner’s testimony against Stevens in a capital case of this nature where petitioner’s lesser culpability was suggested not only by his own confession but was corroborated by testimony of the key witness, has to be below minimal professional standards.
Counsel testified that there were several newspaper accounts of the proceedings between the first and second sentencing hearings and that he was certain that the people in the community were aware of the sentence received at the first trial. App. 55. The record indicates that 23 out of the 35 persons who were asked during voir dire at the second sentencing hearing whether they had heard about the first trial responded affirmatively. Second Tr. 33-34, 40, 48. Counsel made no effort to question these prospective jurors about the extent of their knowledge of the earlier trials and whether it extended to the theories on which petitioner’s and *810Stevens’ trials had been argued. Counsel also testified, in explanation of his failure to seek a change of venue, that he had expected that the jurors who sat at petitioner’s trial would be aware of all the pretrial proceedings, including an unsuccessful effort for change of venue. App. 54-55.
I agree with the observation in the dissenting opinion in the Court of Appeals that the defense “strategy” to make the prosecutor “prove his ease,” see App. 35, “is tantamount to no strategy at all; and reliance upon such a strategy in a capital sentencing proceeding, as an alternative to investigating and presenting available mitigating evidence, is patently unreasonable.” Burger v. Kemp, 753 F. 2d 930, 946 (CA11 1985).