Strickland pled guilty to three counts of murder and several other charges. He was sentenced to death after a hearing before a judge. He then challenged the sentence on the ground that his attorney provided constitutionally inadequate representation at the sentencing proceeding. In the course of rejecting his claim, the Court set out standards for adjudicating ineffective assistance of counsel claims.]

II

In a long line of cases that includes Powell v. Alabama, 287 U.S. 45 (1932), Johnson v. Zerbst, 304 U.S. 458 (1938), and Gideon v. Wainwright, 372 U.S. 335 (1963), this Court has recognized that the Sixth Amendment right to counsel exists, and is needed, in order to protect the fundamental right to a fair trial. The Constitution guarantees a fair trial through the Due Process Clauses, but it defines the basic elements of a fair trial largely through the several provisions of the Sixth Amendment, including the Counsel Clause:

"In all criminal prosecutions, the accused shall enjoy the right to a speedy and public trial, by an impartial jury of the State and district wherein the crime shall have been committed, which district shall have been previously ascertained by law, and to be informed of the nature and cause of the accusation; to be confronted with the witnesses against him; to have compulsory process for obtaining witnesses in his favor, and to have the Assistance of Counsel for his defence."

Thus, a fair trial is one in which evidence subject to adversarial testing is presented to an impartial tribunal for resolution of issues defined in advance of the proceeding. The right to counsel plays a crucial role in the adversarial system embodied in the Sixth Amendment, since access to counsel's skill and knowledge is necessary to accord defendants the "ample opportunity to meet the case of the prosecution" to which they are entitled.

Because of the vital importance of counsel's assistance, this Court has held that, with certain exceptions, a person accused of a federal or state crime has the right to have counsel appointed if retained counsel cannot be obtained. That a person who happens to be a lawyer is present at trial alongside the accused, however, is not enough to satisfy the constitutional command. The Sixth Amendment recognizes the right to the assistance of counsel because it envisions counsel's playing a role that is critical to the ability of the adversarial system to produce just results. An accused is entitled to be assisted by an attorney, whether retained or appointed, who plays the role necessary to ensure that the trial is fair.

For that reason, the Court has recognized that "the right to counsel is the right to the effective assistance of counsel." Government violates the right to effective assistance when it interferes in certain ways with the ability of counsel to make independent decisions about how to conduct the defense. See, e.g., Geders v. United States, 425 U.S. 80 (1976) (bar on attorney-client consultation during overnight recess); Herring v. New York, 422 U.S. 853 (1975) (bar on summation at bench trial); Brooks v. Tennessee, 406 U.S. 605 (1972) (requirement that defendant be first defense witness); Ferguson v. Georgia, 365 U.S. 570 (1961) (bar on direct examination of defendant). Counsel, however, can also deprive a defendant of the right to effective assistance, simply by failing to render "adequate legal assistance," Cuyler v. Sullivan, 446 U.S., at 344 (actual conflict of interest adversely affecting lawyer's performance renders assistance ineffective).

The Court has not elaborated on the meaning of the constitutional requirement of effective assistance in the latter class of cases--that is, those presenting claims of "actual ineffectiveness." In giving meaning to the requirement, however, we must take its purpose--to ensure a fair trial--as the guide. The benchmark for judging any claim of ineffectiveness must be whether counsel's conduct so undermined the proper functioning of the adversarial process that the trial cannot be relied on as having produced a just result.

III

A convicted defendant's claim that counsel's assistance was so defective as to require reversal of a conviction or death sentence has two components. First, the defendant must show that counsel's performance was deficient. This requires showing that counsel made errors so serious that counsel was not functioning as the "counsel" guaranteed the defendant by the Sixth Amendment. Second, the defendant must show that the deficient performance prejudiced the defense. This requires showing that counsel's errors were so serious as to deprive the defendant of a fair trial, a trial whose result is reliable. Unless a defendant makes both showings, it cannot be said that the conviction or death sentence resulted from a breakdown in the adversary process that renders the result unreliable.

A

As all the Federal Courts of Appeals have now held, the proper standard for attorney performance is that of reasonably effective assistance. The Court indirectly recognized as much when it stated in McMann v. Richardson, 397 U.S., at 770, 771, that a guilty plea cannot be attacked as based on inadequate legal advice unless counsel was not "a reasonably competent attorney" and the advice was not "within the range of competence demanded of attorneys in criminal cases." When a convicted defendant complains of the ineffectiveness of counsel's assistance, the defendant must show that counsel's representation fell below an objective standard of reasonableness.

More specific guidelines are not appropriate. The Sixth Amendment refers simply to "counsel," not specifying particular requirements of effective assistance. It relies instead on 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. The proper measure of attorney performance remains simply reasonableness under prevailing professional norms.

Representation of a criminal defendant entails certain basic duties. Counsel's function is to assist the defendant, and hence counsel owes the client a duty of loyalty, a duty to avoid conflicts of interest. From counsel's function as assistant to the defendant derive the overarching duty to advocate the defendant's cause and the more particular duties to consult with the defendant on important decisions and to keep the defendant informed of important developments in the course of the prosecution. Counsel also has a duty to bring to bear such skill and knowledge as will render the trial a reliable adversarial testing process.

These basic duties neither exhaustively define the obligations of counsel nor form a checklist for judicial evaluation of attorney performance. In any case presenting an ineffectiveness claim, the performance inquiry must be whether counsel's assistance was reasonable considering all the circumstances. Prevailing norms of practice as reflected in American Bar Association standards and the like, e.g., ABA Standards for Criminal Justice 4- 1.1 to 4-8.6 (2d ed. 1980) ("The Defense Function"), are guides to determining what is reasonable, but they are only guides. No particular set of detailed rules for counsel's conduct can satisfactorily take account of the variety of circumstances faced by defense counsel or the range of legitimate decisions regarding how best to represent a criminal defendant. Any such set of rules would interfere with the constitutionally protected independence of counsel and restrict the wide latitude counsel must have in making tactical decisions. Indeed, the existence of detailed guidelines for representation could distract counsel from the overriding mission of vigorous advocacy of the defendant's cause. Moreover, the purpose of the effective assistance guarantee of the Sixth Amendment is not to improve the quality of legal representation, although that is a goal of considerable importance to the legal system. The purpose is simply to ensure that criminal defendants receive a fair trial.

Judicial scrutiny of counsel's performance must be highly deferential. It is all too tempting for a defendant to second-guess counsel's assistance after conviction or adverse sentence, and it is all too easy for a court, examining counsel's defense after it has proved unsuccessful, to conclude that a particular act or omission of counsel was unreasonable. A fair assessment of attorney performance requires that every effort be made to eliminate the distorting effects of hindsight, to reconstruct the circumstances of counsel's challenged conduct, and to evaluate the conduct from counsel's perspective at the time. Because of the difficulties inherent in making the evaluation, a court must indulge a strong presumption that counsel's conduct falls within the wide range of reasonable professional assistance; that is, the defendant must overcome the presumption that, under the circumstances, the challenged action "might be considered sound trial strategy." There are countless ways to provide effective assistance in any given case. Even the best criminal defense attorneys would not defend a particular client in the same way. See Goodpaster, The Trial for Life: Effective Assistance of Counsel in Death Penalty Cases, 58 N.Y.U.L.Rev. 299, 343 (1983).

The availability of intrusive post-trial inquiry into attorney performance or of detailed guidelines for its evaluation would encourage the proliferation of ineffectiveness challenges. Criminal trials resolved unfavorably to the defendant would increasingly come to be followed by a second trial, this one of counsel's unsuccessful defense. Counsel's performance and even willingness to serve could be adversely affected. Intensive scrutiny of counsel and rigid requirements for acceptable assistance could dampen the ardor and impair the independence of defense counsel, discourage the acceptance of assigned cases, and undermine the trust between attorney and client.

These standards require no special amplification in order to define counsel's duty to investigate, the duty at issue in this case. As the Court of Appeals concluded, strategic choices made after thorough investigation of law and facts relevant to plausible options are virtually unchallengeable; and strategic choices made after less 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.

The reasonableness of counsel's actions may be determined or substantially influenced by the defendant's own statements or actions. Counsel's actions are usually based, quite properly, on informed strategic choices made by the defendant and on information supplied by the defendant. In particular, what investigation decisions are reasonable depends critically on such information. For example, when the facts that support a certain potential line of defense are generally known to counsel because of what the defendant has said, the need for further investigation may be considerably diminished or eliminated altogether. And when a defendant has given counsel reason to believe that pursuing certain investigations would be fruitless or even harmful, counsel's failure to pursue those investigations may not later be challenged as unreasonable. In short, inquiry into counsel's conversations with the defendant may be critical to a proper assessment of counsel's investigation decisions, just as it may be critical to a proper assessment of counsel's other litigation decisions.

B

In certain Sixth Amendment contexts, prejudice is presumed. Actual or constructive denial of the assistance of counsel altogether is legally presumed to result in prejudice. So are various kinds of state interference with counsel's assistance. Prejudice in these circumstances is so likely that case-by-case inquiry into prejudice is not worth the cost. Moreover, such circumstances involve impairments of the Sixth Amendment right that are easy to identify and, for that reason and because the prosecution is directly responsible, easy for the government to prevent.

One type of actual ineffectiveness claim warrants a similar, though more limited, presumption of prejudice. In Cuyler v. Sullivan, the Court held that prejudice is presumed when counsel is burdened by an actual conflict of interest. In those circumstances, counsel breaches the duty of loyalty, perhaps the most basic of counsel's duties. Moreover, it is difficult to measure the precise effect on the defense of representation corrupted by conflicting interests. Given the obligation of counsel to avoid conflicts of interest and the ability of trial courts to make early inquiry in certain situations likely to give rise to conflicts, see, e.g., Fed.Rule Crim.Proc. 44(c), it is reasonable for the criminal justice system to maintain a fairly rigid rule of presumed prejudice for conflicts of interest. Even so, the rule is not quite the per se rule of prejudice that exists for the Sixth Amendment claims mentioned above. Prejudice is presumed only if the defendant demonstrates that counsel "actively represented conflicting interests" and that "an actual conflict of interest adversely affected his lawyer's performance."

Conflict of interest claims aside, actual ineffectiveness claims alleging a deficiency in attorney performance are subject to a general requirement that the defendant affirmatively prove prejudice. The government is not responsible for, and hence not able to prevent, attorney errors that will result in reversal of a conviction or sentence. Attorney errors come in an infinite variety and are as likely to be utterly harmless in a particular case as they are to be prejudicial. They cannot be classified according to likelihood of causing prejudice. Nor can they be defined with sufficient precision to inform defense attorneys correctly just what conduct to avoid. Representation is an art, and an act or omission that is unprofessional in one case may be sound or even brilliant in another. Even if a defendant shows that particular errors of counsel were unreasonable, therefore, the defendant must show that they actually had an adverse effect on the defense.

It is not enough for the defendant to show that the errors had some conceivable effect on the outcome of the proceeding. Virtually every act or omission of counsel would meet that test, and not every error that conceivably could have influenced the outcome undermines the reliability of the result of the proceeding. Respondent suggests requiring a showing that the errors "impaired the presentation of the defense." That standard, however, provides no workable principle. Since any error, if it is indeed an error, "impairs" the presentation of the defense, the proposed standard is inadequate because it provides no way of deciding what impairments are sufficiently serious to warrant setting aside the outcome of the proceeding.

On the other hand, we believe that a defendant need not show that counsel's deficient conduct more likely than not altered the outcome in the case. This outcome-determinative standard has several strengths. It defines the relevant inquiry in a way familiar to courts, though the inquiry, as is inevitable, is anything but precise. The standard also reflects the profound importance of finality in criminal proceedings. Moreover, it comports with the widely used standard for assessing motions for new trial based on newly discovered evidence. Nevertheless, the standard is not quite appropriate.

Even when the specified attorney error results in the omission of certain evidence, the newly discovered evidence standard is not an apt source from which to draw a prejudice standard for ineffectiveness claims. The high standard for newly discovered evidence claims presupposes that all the essential elements of a presumptively accurate and fair proceeding were present in the proceeding whose result is challenged. An ineffective assistance claim asserts the absence of one of the crucial assurances that the result of the proceeding is reliable, so finality concerns are somewhat weaker and the appropriate standard of prejudice should be somewhat lower. The result of a proceeding can be rendered unreliable, and hence the proceeding itself unfair, even if the errors of counsel cannot be shown by a preponderance of the evidence to have determined the outcome.

In making the determination whether the specified errors resulted in the required prejudice, a court should presume, absent challenge to the judgment on grounds of evidentiary insufficiency, that the judge or jury acted according to law. An assessment of the likelihood of a result more favorable to the defendant must exclude the possibility of arbitrariness, whimsy, caprice, "nullification," and the like. A defendant has no entitlement to the luck of a lawless decisionmaker, even if a lawless decision cannot be reviewed. The assessment of prejudice should proceed on the assumption that the decisionmaker is reasonably, conscientiously, and impartially applying the standards that govern the decision. It should not depend on the idiosyncracies of the particular decisionmaker, such as unusual propensities toward harshness or leniency. Although these factors may actually have entered into counsel's selection of strategies and, to that limited extent, may thus affect the performance inquiry, they are irrelevant to the prejudice inquiry. Thus, evidence about the actual process of decision, if not part of the record of the proceeding under review, and evidence about, for example, a particular judge's sentencing practices, should not be considered in the prejudice determination.

The governing legal standard plays a critical role in defining the question to be asked in assessing the prejudice from counsel's errors. When a defendant challenges a conviction, the question is whether there is a reasonable probability that, absent the errors, the factfinder would have had a reasonable doubt respecting guilt. When a defendant challenges a death sentence such as the one at issue in this case, the question is whether there is a reasonable probability that, absent the errors, the sentencer--including an appellate court, to the extent it independently reweighs the evidence--would have concluded that the balance of aggravating and mitigating circumstances did not warrant death.

In making this determination, a court hearing an ineffectiveness claim must consider the totality of the evidence before the judge or jury. Some of the factual findings will have been unaffected by the errors, and factual findings that were affected will have been affected in different ways. Some errors will have had a pervasive effect on the inferences to be drawn from the evidence, altering the entire evidentiary picture, and some will have had an isolated, trivial effect. Moreover, a verdict or conclusion only weakly supported by the record is more likely to have been affected by errors than one with overwhelming record support. Taking the unaffected findings as a given, and taking due account of the effect of the errors on the remaining findings, a court making the prejudice inquiry must ask if the defendant has met the burden of showing that the decision reached would reasonably likely have been different absent the errors.

IV

A number of practical considerations are important for the application of the standards we have outlined. Most important, in adjudicating a claim of actual ineffectiveness of counsel, a court should keep in mind that the principles we have stated do not establish mechanical rules. Although those principles should guide the process of decision, the ultimate focus of inquiry must be on the fundamental fairness of the proceeding whose result is being challenged. In every case the court should be concerned with whether, despite the strong presumption of reliability, the result of the particular proceeding is unreliable because of a breakdown in the adversarial process that our system counts on to produce just results. . . .

Although we have discussed the performance component of an ineffectiveness claim prior to the prejudice component, there is no reason for a court deciding an ineffective assistance claim to approach the inquiry in the same order or even to address both components of the inquiry if the defendant makes an insufficient showing on one. In particular, a court need not determine whether counsel's performance was deficient before examining the prejudice suffered by the defendant as a result of the alleged deficiencies. The object of an ineffectiveness claim is not to grade counsel's performance. If it is easier to dispose of an ineffectiveness claim on the ground of lack of sufficient prejudice, which we expect will often be so, that course should be followed. Courts should strive to ensure that ineffectiveness claims not become so burdensome to defense counsel that the entire criminal justice system suffers as a result.

* * *

Justice MARSHALL, dissenting.

* * *

The opinion of the Court revolves around two holdings. First, the majority ties the constitutional minima of attorney performance to a simple "standard of reasonableness." Second, the majority holds that only an error of counsel that has sufficient impact on a trial to "undermine confidence in the outcome" is grounds for overturning a conviction. I disagree with both of these rulings.

A

My objection to the performance standard adopted by the Court is that it is so malleable that, in practice, it will either have no grip at all or will yield excessive variation in the manner in which the Sixth Amendment is interpreted and applied by different courts. To tell lawyers and the lower courts that counsel for a criminal defendant must behave "reasonably" and must act like "a reasonably competent attorney," is to tell them almost nothing. In essence, the majority has instructed judges called upon to assess claims of ineffective assistance of counsel to advert to their own intuitions regarding what constitutes "professional" representation, and has discouraged them from trying to develop more detailed standards governing the performance of defense counsel. In my view, the Court has thereby not only abdicated its own responsibility to interpret the Constitution, but also impaired the ability of the lower courts to exercise theirs.

The debilitating ambiguity of an "objective standard of reasonableness" in this context is illustrated by the majority's failure to address important issues concerning the quality of representation mandated by the Constitution. It is an unfortunate but undeniable fact that a person of means, by selecting a lawyer and paying him enough to ensure he prepares thoroughly, usually can obtain better representation than that available to an indigent defendant, who must rely on appointed counsel, who, in turn, has limited time and resources to devote to a given case. Is a "reasonably competent attorney" a reasonably competent adequately paid retained lawyer or a reasonably competent appointed attorney? It is also a fact that the quality of representation available to ordinary defendants in different parts of the country varies significantly. Should the standard of performance mandated by the Sixth Amendment vary by locale The majority offers no clues as to the proper responses to these questions.

The majority defends its refusal to adopt more specific standards primarily on the ground that "[n]o particular set of detailed rules for counsel's conduct can satisfactorily take account of the variety of circumstances faced by defense counsel or the range of legitimate decisions regarding how best to represent a criminal defendant." I agree that counsel must be afforded "wide latitude" when making "tactical decisions" regarding trial strategy, but many aspects of the job of a criminal defense attorney are more amenable to judicial oversight. For example, much of the work involved in preparing for a trial, applying for bail, conferring with one's client, making timely objections to significant, arguably erroneous rulings of the trial judge, and filing a notice of appeal if there are colorable grounds therefor could profitably be made the subject of uniform standards.

The opinion of the Court of Appeals in this case represents one sound attempt to develop particularized standards designed to ensure that all defendants receive effective legal assistance. . . . By refusing to address the merits of these proposals, and indeed suggesting that no such effort is worthwhile, the opinion of the Court, I fear, will stunt the development of constitutional doctrine in this area.

B

I object to the prejudice standard adopted by the Court for two independent reasons. First, it is often very difficult to tell whether a defendant convicted after a trial in which he was ineffectively represented would have fared better if his lawyer had been competent. Seemingly impregnable cases can sometimes be dismantled by good defense counsel. On the basis of a cold record, it may be impossible for a reviewing court confidently to ascertain how the government's evidence and arguments would have stood up against rebuttal and cross-examination by a shrewd, well-prepared lawyer. The difficulties of estimating prejudice after the fact are exacerbated by the possibility that evidence of injury to the defendant may be missing from the record precisely because of the incompetence of defense counsel. In view of all these impediments to a fair evaluation of the probability that the outcome of a trial was affected by ineffectiveness of counsel, it seems to me senseless to impose on a defendant whose lawyer has been shown to have been incompetent the burden of demonstrating prejudice.

Second and more fundamentally, the assumption on which the Court's holding rests is that the only purpose of the constitutional guarantee of effective assistance of counsel is to reduce the chance that innocent persons will be convicted. In my view, the guarantee also functions to ensure that convictions are obtained only through fundamentally fair procedures. The majority contends that the Sixth Amendment is not violated when a manifestly guilty defendant is convicted after a trial in which he was represented by a manifestly ineffective attorney. I cannot agree. Every defendant is entitled to a trial in which his interests are vigorously and conscientiously advocated by an able lawyer. A proceeding in which the defendant does not receive meaningful assistance in meeting the forces of the State does not, in my opinion, constitute due process.

In Chapman v. California, 386 U.S. 18 (1967), we acknowledged that certain constitutional rights are "so basic to a fair trial that their infraction can never be treated as harmless error." Among these rights is the right to the assistance of counsel at trial. In my view, the right to effective assistance of counsel is entailed by the right to counsel, and abridgment of the former is equivalent to abridgment of the latter. I would thus hold that a showing that the performance of a defendant's lawyer departed from constitutionally prescribed standards requires a new trial regardless of whether the defendant suffered demonstrable prejudice thereby.

Even if I were inclined to join the majority's two central holdings, I could not abide the manner in which the majority elaborates upon its rulings. Particularly regrettable are the majority's discussion of the "presumption" of reasonableness to be accorded lawyers' decisions and its attempt to prejudge the merits of claims previously rejected by lower courts using different legal standards.

A

In defining the standard of attorney performance required by the Constitution, the majority appropriately notes that many problems confronting criminal defense attorneys admit of "a range of legitimate" responses. And the majority properly cautions courts, when reviewing a lawyer's selection amongst a set of options, to avoid the hubris of hindsight. The majority goes on, however, to suggest that reviewing courts should "indulge a strong presumption that counsel's conduct" was constitutionally acceptable, and should "appl[y] a heavy measure of deference to counsel's judgments,"

I am not sure what these phrases mean, and I doubt that they will be self-explanatory to lower courts. If they denote nothing more than that a defendant claiming he was denied effective assistance of counsel has the burden of proof, I would agree. But the adjectives "strong" and "heavy" might be read as imposing upon defendants an unusually weighty burden of persuasion. If that is the majority's intent, I must respectfully dissent. The range of acceptable behavior defined by "prevailing professional norms," seems to me sufficiently broad to allow defense counsel the flexibility they need in responding to novel problems of trial strategy. To afford attorneys more latitude, by "strongly presuming" that their behavior will fall within the zone of reasonableness, is covertly to legitimate convictions and sentences obtained on the basis of incompetent conduct by defense counsel.

The only justification the majority itself provides for its proposed presumption is that undue receptivity to claims of ineffective assistance of counsel would encourage too many defendants to raise such claims and thereby would clog the courts with frivolous suits and "dampen the ardor" of defense counsel. I have more confidence than the majority in the ability of state and federal courts expeditiously to dispose of meritless arguments and to ensure that responsible, innovative lawyering is not inhibited. In my view, little will be gained and much may be lost by instructing the lower courts to proceed on the assumption that a defendant's challenge to his lawyer's performance will be insubstantial.