Opinion
GEORGE, J.In People v. Jackson (1980) 28 Cal.3d 264 [618 P.2d 149] (Jackson I), we affirmed a judgment against petitioner Earl Lloyd Jackson (hereafter defendant), who is currently confined in state prison under a sentence of death imposed pursuant to that judgment for the 1977 murder of two elderly women. In 1981, after the judgment on appeal became final, defendant filed a petition for writ of habeas corpus in which he sought relief on a variety of grounds. On November 27, 1981, we issued an order to show cause, subsequently appointed a referee, and after a series of orders adding and eliminating several matters from the referee’s consideration, ultimately directed the referee to take evidence and make findings of fact relating to the following three issues: (1) whether the admissions defendant made to two jailhouse informants, Mark Mikles and Ronald McFarland, deliberately were elicited from defendant at the behest of law enforcement officials so as to render the statements inadmissible at trial under the principles set forth in United States v. Henry (1980) 447 U.S. 264 [65 L.Ed.2d 115, 100 S.Ct. 2183]; (2) whether the prosecution improperly failed to disclose to the defense any inducements offered by state agents to Mikles or McFarland for their testimony at defendant’s trial; and (3) whether defendant’s trial counsel failed to provide adequate representation with respect to the special circumstance allegations or the penalty phase of the trial.
After an extensive evidentiary hearing, the referee found that (1) Mikles and McFarland had not elicited statements from defendant at the behest of law enforcement officials, but (2) state officials had offered inducements to Mikles and McFarland for their testimony that had not been disclosed to the defense, and (3) defendant’s trial counsel had failed to provide adequate representation with respect to both the special circumstance allegations and the penalty phase. The referee also indicated that, in his view, these constitutional violations required reversal of the special circumstance findings and the judgment as to penalty.
Defendant has not challenged the referee’s finding that his admissions to the jailhouse informants were not elicited by law enforcement officials in *585violation of the holding in United States v. Henry, supra, 447 U.S. 264, and the record supports this finding, which accordingly we adopt.1
The Attorney General, however, contests the referee’s findings both with regard to the prosecution’s asserted failure to disclose to the defense the inducements provided to Mikles and McFarland, and with regard to the alleged inadequacy of the legal representation provided by trial counsel. Additionally, the Attorney General argues that even if the referee’s findings on those issues are sustained, they do not provide a sufficient basis for overturning the special circumstance findings or the judgment as to penalty.
After summarizing the facts underlying defendant’s conviction, we analyze the referee’s findings with respect to (1) the prosecution’s alleged failure to disclose inducements made to prosecution witnesses, and (2) the alleged ineffective assistance provided by defendant’s trial counsel with regard to the special circumstance allegations and the penalty phase. “Our standard of review of the referee’s report is settled. The referee’s conclusions of law are subject to independent review, as is his resolution of mixed questions of law and fact. [Citations.] . . . The referee’s findings of fact, though not binding on the court, are given great weight when supported by substantial evidence. The deference accorded factual findings derives from the fact that the referee had the opportunity to observe the demeanor of witnesses and their manner of testifying. [Citation.]” (In re Marquez (1992) 1 Cal.4th 584, 603 [3 Cal.Rptr.2d 727, 822 P.2d 435].)
More than 10 years after our grant of habeas corpus review, and in the aftermath of judicial proceedings beset by extended delay reminiscent of that described in Charles Dickens’s Bleak House, we reject defendant’s claim *586that errors at his 1978-1979 trial require that the judgment sentencing him to death be set aside.2
I. Evidence Received at Trial
In our opinion on defendant’s automatic appeal, we summarized the evidence presented at trial (Jackson I, supra, 28 Cal.3d 264, 283-285) and thus need recount those facts only briefly here.
The evidence disclosed that on 2 separate occasions within a 10-day period, defendant (then 19 years of age), accompanied by 1 or more other persons, burglarized the apartments of 2 elderly women, Mrs. Vernita Curtis, who was 81 years of age, and Mrs. Gladys Ott, who was 90 years of age. Both women resided in the same apartment building in which defendant *587temporarily was staying, and the motive on both occasions apparently was to steal money or other items of value; in both instances, television sets, toasters, and other household or personal items were taken.
At the time of each burglary, the elderly resident was asleep in her apartment and apparently awoke, discovering the intruders while the crime was in progress. The perpetrators responded to the victims’ protests by severely beating the elderly women with blows to the head, neck, and chest. In the first incident, Mrs. Curtis still was alive when discovered by her neighbors but, after four days of hospitalization, died from the severe injuries inflicted upon her. In the second incident, Mrs. Ott was dead when discovered, and appeared to have been beaten, and perhaps strangled, to death. The autopsy of Mrs. Ott revealed, in addition to massive bruises to her face, neck, and body, an extensive vaginal laceration apparently caused by the insertion of a foreign object into her vagina.
On learning that the police were looking for him, defendant went to a police station and agreed to make a tape-recorded statement. After initially denying participation in the crimes, defendant ultimately admitted that he and others had burglarized both apartments. In his statement to the police, however, defendant denied having been the person who inflicted the severe beatings on the victims, claiming with respect to Mrs. Curtis that he simply held her while another participant struck her, and with respect to Mrs. Ott that others inflicted the majority of the blows, that he struck her only once, and that he believed she was alive when he left her apartment.
In addition to introducing defendant’s statement to the police, the prosecution presented a number of witnesses who testified to statements defendant made to them admitting his complicity in the crimes. A neighbor, llena Gaines, testified that when Mrs. Curtis was being removed from her apartment on a stretcher, defendant was standing outside the building and smiled, laughed, and stated “he was the one who did that.’’3 The prosecution also introduced a transcript of the preliminary hearing testimony of Debria Lewis, another acquaintance of defendant, who stated that shortly after the killings defendant pointed to a newspaper article concerning Mrs. Curtis’s murder and stated, “This is what I done.” Lewis stated that when she asked defendant for an explanation, he replied: “If she had just been still—had been still and given him the money, that she would have been walking *588around today.” In this same conversation defendant described the two victims to Lewis as “two old bags [who] were a nuisance and . . . got what they deserved.” The prosecution also called Debra Hall, defendant’s cousin, who testified that defendant had told her, in reference to a news article concerning both victims, that “This is what I did, that it was because I needed some money.”
Finally, in addition to the above evidence, the prosecution called as witnesses the two jailhouse informants, Mikles and McFarland, referred to above. Each informant testified that defendant, in separate conversations with each of them during his confinement after arrest, made detailed admissions as to his actions during the burglaries.4 Both testified that defendant admitted killing the two women and boasted about repeatedly striking Mrs. Ott in the face and forcibly inserting a wine bottle into her vagina.5
The defense did not present any evidence at the guilt phase.
*589On the basis of the foregoing evidence, the jury convicted defendant of two counts of first degree murder and two counts of burglary, finding true the two special circumstance allegations—a burglary-murder special circumstance and a multiple-murder special circumstance—alleged, under the applicable 1977 death penalty law, with respect to the killing of Mrs. Ott.
At the penalty phase, the prosecution introduced evidence that the neck of a wine bottle found close to Mrs. Ott’s body contained two hairs that appeared to be similar to the pubic hairs of the victim, and that there appeared to be dried blood on the neck of the bottle and in the area of the victim’s vagina. Defense counsel cross-examined the prosecution witnesses and made a lengthy closing argument, but again did not introduce any evidence on defendant’s behalf. The jury fixed the penalty at death.
As noted, on appeal we affirmed the judgment in all respects.
II. Inducements Offered to Jailhouse-informant Witnesses
In testifying at defendant’s trial, both Mikles and McFarland stated explicitly, in response to questioning by the deputy district attorney, that they had not received any promises from any law enforcement officials in exchange for their testimony against defendant. Although both witnesses acknowledged currently being either under sentence or facing sentence on a number of charges, they denied that anyone had promised to take any action on their behalf in the event they testified against defendant.
One exchange between the prosecutor and Mikles—the first of the two jailhouse informants to testify at trial—was particularly explicit on this subject. The deputy district attorney questioned Mikles as follows:
“Q. Now, had you ever asked anyone—the sheriffs, District Attorney, police—anything in return for your telling them about the statement that Jackson made to you?
“A. Have I ever been promised anything?
“Q. Well, for example, did you ever tell any officer or DA or sheriff, Hey, I have got something to tell you, but you have to give me something in return? And I will tell you only if you give me something. Anything like that?
*590“A. No. It doesn’t work that way.
“Q. Did you talk to me today for about five minutes around 11:15?
“A. Yeah. I think it was less than that. About a minute or two.
“Q. Is that the first time that you talked to me?
“A. Yes, it is.
“Q. And during that conversation did you ask me to do anything for you?
“A. No, I did not.
“Q. Did I tell you I would do anything or that anyone would do anything for you in exchange for your testifying?
“A. No.
“Q. All right. Now, did anyone, up to the time that you have testified now on this witness stand—did anyone—when I say, ‘anyone,’ I include sheriffs, police, District Attorneys; in other words, anyone in law enforcement—did anyone—probation officers—did anyone promise you anything in exchange for your testifying about the conversation that Jackson had with you?
“A. Just a lot of protection.
“Q. Pardon?
“A. Just a lot of protection.
“Q. Just a lot of protection?
“A. Yeah.
“Q. Is that about all?
“A. That’s it.
“Q. And who, incidentally, promised you protection?
*591“A. The Sheriff’s Department did.”
The relevant exchange between the deputy district attorney and McFarland was briefer but similar in substance:
“Q. Mr. McFarland, is it true that you saw me for the first time last week?
“A. Yes, sir.
“Q. And is it true that no one promised you anything in exchange for your testimony against Mr. Jackson?
“A. Yes, that’s right.
“Q. Now, when you were up in this court last June 23, 1978, when you were convicted by way of being sentenced on the robbery charges of which this Court found you guilty, as you indicated, was I here in court?
“A. No, sir.
“Q. Was there a District Attorney present at the time that you were sentenced and convicted on that date of June 23, ’78?
“A. Yes, sir.
“Q. And did that District Attorney make any statements in your presence to the Court that the sentence should be lenient because you were going to testify in the Jackson case?
“A. No, sir.”
Although both Mikles and McFarland thus testified at defendant’s trial that they had received no promises of assistance from any state officials for their trial testimony, during the course of their testimony in the reference hearing in connection with defendant’s ineffective-assistance-of-counsel claim (discussed below), both Mikles and McFarland made a number of statements that appeared inconsistent with their trial testimony. On defense counsel’s motion, we expanded the scope of the reference hearing, directing the referee to take evidence, and ultimately to make findings, on the question whether any offers or inducements had been made by the prosecution or other state agents for the testimony of either witness and, if so, whether such offers or inducements had been disclosed to the defense.
Based on the evidence presented at the reference hearing, the referee found that inducements had in fact been made by state agents to both Mikles *592and McFarland for their testimony at defendant’s trial and that the prosecution had failed to disclose these inducements to defendant or his trial counsel.
With respect to Mikles, the evidence at the reference hearing revealed that when Mikles contacted members of the sheriff’s department and police department, indicating he had information relevant to defendant’s case, he informed the law enforcement officers that in exchange for his testimony against defendant he wanted assistance in (1) having a six-year sentence, previously imposed on him in Long Beach, recalled and reduced, (2) receiving as little time, or, if possible, no time, on a number of charges then pending against him in Norwalk, and (3) having a potential forty-two-month sentence for a federal parole violation reduced or eliminated. Mikles testified that members of the sheriff’s and police departments promised him that although they could not guarantee any specific results, if he testified for the prosecution in defendant’s case and in other cases in which he claimed he had obtained incriminating evidence against other inmates, they would bring his cooperation to the attention of the judges and deputy district attorneys involved in his cases and use their best efforts to help him achieve his objectives as described above.
Mildes’s account was confirmed by the testimony of a Los Angeles Deputy Sheriff who had acted as Mikles’s principal contact with the officers assigned to the specific crimes as to which Mikles had relevant information. The deputy sheriff testified: “I think it’s one of the standard procedures, if an informant is working for you, that you will let the information be known that he did work and, you know, he provided productive information.” She continued: “What I told Mr. Mikles I would do is if his information was productive information, and it could be used, and we could get a conviction, I would advise the district attorney that was handling his case of his assistance to us.”6
The referee also found, from the evidence presented at the hearing, that after defendant’s trial the inducements promised to Mikles were in fact *593provided to him. The law enforcement officers with whom Mikles had spoken wrote letters and gave statements on Mi kies’s behalf in a number of proceedings, which led to a very significant reduction in the sentences previously imposed on Mikles and to the dismissal of most of the additional charges then pending against him.7
With regard to McFarland, the evidence at the reference hearing indicated that the prosecutor in defendant’s case had promised to write a letter on McFarland’s behalf at the conclusion of defendant’s trial, recommending that the relevant prison authorities permit McFarland to serve his time in Arizona, where his family lived, rather than in California.8
The Attorney General concedes that the evidence presented at the reference hearing supports the referee’s findings that the foregoing offers of assistance or inducements were made to both Mikles and McFarland prior to defendant’s trial and were not disclosed to the defense. The Attorney General argues, however, that (1) the offers or inducements at issue here were not the kind of inducements the prosecution was constitutionally compelled to disclose to the defense, and (2) in any event, the failure to disclose the inducements was not prejudicial.
As the Attorney General acknowledges, in People v. Morris (1988) 46 Cal.3d 1 [249 Cal.Rptr. 119, 756 P.2d 843], this court discussed at some length the legal principles governing the prosecution’s duty to disclose inducements made to prosecution witnesses and to correct misleading statements made by such witnesses with regard to such inducements.
We stated in Morris: “It is well settled that the prosecution has a duty to disclose all substantial material evidence favorable to an accused. [Citations.] That duty exists regardless of whether there has been a request for such evidence [citation] and irrespective of whether the suppression was *594intentional or inadvertent. [Citation.] As the United States Supreme Court in the seminal case of Brady v. Maryland (1963) 373 U.S. 83, 87 [10 L.Ed.2d 215, 218-219, 83 S.Ct. 1194], succinctly stated: ‘[T]he suppression by the prosecution of evidence favorable to an accused . . . violates due process . . . irrespective of the good faith or bad faith of the prosecution.’ [][] The duty to disclose evidence favorable to the accused extends to evidence which may reflect on the credibility of a material witness. [Citation.] As this court said in [People v.] Ruthford [(1975) 14 Cal.3d 399 [121 Cal.Rptr. 261, 534 P.2d 1341, A.L.R.4th 3132]], ‘[Suppression of substantial material evidence bearing on the credibility of a key prosecution witness is a denial of due process . . . .’ [Citation.] [*][] The duty to disclose evidence bearing on the credibility of a prosecution witness manifestly includes any promises or inducements that have been made to obtain the witness’s testimony. As we recently explained in People v. Phillips, [(1985)] 41 Cal.3d [29,] 46 [222 Cal.Rptr. 127, 711 P.2d 423], ‘[s]ince a witness’s credibility depends heavily on his motive for testifying, the prosecution must disclose to the defense and jury any inducements made to a prosecution witness to testify and must also correct any false or misleading testimony by the witness relating to any inducements.' ” (Morris, supra, 46 Cal.3d at pp. 29-30, italics added by Morris.)
In his brief, the Attorney General acknowledges “that under People v. Morris[, supra,] 46 Cal.3d 1, 24-34, the offers made to Mr. McFarland and Mr. Mi kies were inducements which constituted substantial material evidence bearing on the credibility of both witnesses and should have been disclosed to the defense.” The Attorney General argues, however, that the decision in Morris adopted an improper standard for determining whether evidence constitutes “substantial material evidence” which the prosecution is under a constitutional duty to disclose, and he urges us to reconsider this aspect of our decision in Morris.
In Morris, we specifically rejected the People’s contention “that evidence is ‘material’ only if there is a reasonable probability that its disclosure would affect the verdict,” and concluded that “the prosecution’s duty of disclosure extends to all evidence that reasonably appears favorable to the accused, not merely to that evidence which appears likely to affect the verdict.” (Morris, supra, 46 Cal.3d 1, 30, fn. 14, original italics.) The Attorney General contends, however, that Morris's holding on this point overlooked a pertinent passage in the United States Supreme Court’s decision in United States v. Agurs (1976) 427 U.S. 97, 112-113 [49 L.Ed.2d 342, 354-355, 96 S.Ct. 2392], and that Agurs supports the position, explicitly rejected in Morris, that the prosecution has a duty to disclose “only that evidence which has a reasonable probability of affecting the verdict if disclosed.” (See also United *595States v. Bagley (1985) 473 U.S. 667, 681-683 [87 L.Ed.2d 481, 493-495, 105 S.Ct. 3375].)
In the present case, however, we need not determine whether the Morris decision properly interpreted the concept of “substantial material evidence” as discussed in applicable federal authority governing the prosecution’s general constitutional obligation of disclosure, or whether, under that standard, the evidence of inducements in the present case constituted substantial material evidence subject to disclosure. Here, the prosecution’s obligation to disclose the inducements provided to the jailhouse informants rested not simply on the prosecution’s general duty to disclose “all substantial material evidence” to the defendant, but on its distinct and in some respects more basic duty, also explicitly recognized in Agurs, to correct any testimony of its own witnesses which it knew, or should have known, was false or misleading. (See United States v. Agurs, supra, 427 U.S. at pp. 103-104 [49 L.Ed.2d at pp. 349-350], See also Napue v. Illinois (1959) 360 U.S. 264 [3 L.Ed.2d 1217, 79 S.Ct. 1173]; Giglio v. United States (1972) 405 U.S. 150 [31 L.Ed.2d 104, 92 S.Ct. 763].)
As noted above, at defendant’s trial the deputy district attorney specifically elicited testimony from both Mikles and McFarland affirmatively stating that these witnesses had received no promises from anyone in return for their testimony. Although the prosecutor testified at the reference hearing that at the time of trial he was personally unaware of the promises of assistance that had been made to Mikles by members of the sheriff’s and police departments, the governing federal decisions establish that the trial prosecutor’s lack of personal knowledge of the false and misleading nature of a prosecution witness’s testimony is not controlling. The United States Supreme Court has held that the state’s duty to correct false or misleading testimony by prosecution witnesses applies to testimony which the prosecution knows, or should know, is false or misleading (see United States v. Agurs, supra, 427 U.S. at p. 103 [49 L.Ed.2d at pp. 349-350]), and has concluded this obligation applies to testimony whose false or misleading character would be evident in light of information known to other prosecutors, to the police, or to other investigative agencies involved in the criminal prosecution. (See, e.g., Giglio v. United States, supra, 405 U.S. 150, 154 [31 L.Ed.2d 104, 108-109] [information known to prior prosecutor]; United States v. Bagley, supra, 473 U.S. 667, 670-672 & fn. 4 [87 L.Ed.2d 481, 486-488] [information known to federal investigators]; Barbee v. Warden, Maryland Penitentiary (4th Cir. 1964) 331 F.2d 842, 846 [information known to investigating police officers]. See also Comment, The Prosecutor’s Duty [to] Disclose: From Brady to Agurs and Beyond (1978) 69 J.Crim.L. & Criminology 197, 205-206; 2 LaFave & Israel, Criminal Procedure (1984) *596§ 19.5, pp. 553-534 & fn. 9.) Because in this case the inducements made to Mikles were known to, and indeed had been made by, the investigating officers who brought the informants to the prosecutor’s attention, the prosecution had a duty to correct the false testimony concerning such inducements.9
The Attorney General additionally argues that disclosure of the inducements was not required in this instance because the prosecutor testified at the reference hearing that he had understood the witnesses’s testimony at trial—stating no “promises” had been made to them—to mean only that no promises of “guaranteed results” had been made to them; the Attorney General thus argues that, as so interpreted, the witnesses’s testimony was neither false nor misleading. Their testimony at trial, however, was not explicitly qualified and was apt to be misleading to a lay jury. (See, e.g., United States v. Bagley, supra, 473 U.S. at pp. 683-684 [87 L.Ed.2d at pp. 494-495].) Although promises of “guaranteed results” may not have been made to the informants, the requirement of disclosure is not limited to inducements that take the form of a “guaranteed” benefit. Indeed, a number of recent decisions have observed that there may be an even greater danger that a witness may lie when the potential benefits that may flow from the witness’s testimony are not specified ahead of time, than when the witness has been promised a specified benefit. (See, e.g., Morris, supra, 46 Cal.3d 1, 32; People v. Phillips (1985) 41 Cal.3d 29, 47-48 [222 Cal.Rptr. 127, 711 P.2d 423].)
The recent Morris decision, which involved a similar commitment by law enforcement officers to use their best efforts to assist a prosecution witness in return for his testimony, speaks directly to this point: “‘[U]nless the witness is informed both of the terms of the agreement and that his receipt of the benefit cannot be denied so long as he testified fully and truthfully at the criminal trial, the witness cannot help but believe that his own treatment will depend on how “well” he does. ... [A] prosecutor’s [or police officer’s] insistence that the witness not be informed of the terms of the bargain has the inevitable tendency to lead the witness to color his testimony, so as to receive the most favorable treatment from the prosecutor.’ ” (Morris, supra, 46 Cal.3d at p. 32, italics in original, bracketed phrase added. See also *597United States v. Bagley, supra, 473 U.S. 667, 683 [87 L.Ed.2d 481, 494-495].)
In fact, the testimony at the reference hearing of the deputy sheriff who dealt most directly with Mikles inadvertently revealed that the deputy may well have conveyed to Mikles the improper message that the treatment Mikles would receive would depend on how “well” he performed. As noted above, the deputy sheriff testified: “What I told Mr. Mikles I would do is if his information was productive information, and it could be used, and we could get a conviction, I would advise the district attorney that was handling his case of his assistance to us.” (Italics added.) Past cases establish that the state may not offer a witness an inducement conditioned on the state’s obtaining a conviction based on the witness’s testimony, and that testimony elicited on the basis of such a condition may not properly be admitted at trial. (See, e.g., People v. Green (1951) 102 Cal.App.2d 831 [228 P.2d 867].) The Attorney General contends that the remainder of the deputy sheriff’s testimony at the evidentiary hearing suggests that the deputy may have misspoken in stating she had informed Mikles that the authorities would assist him in attempting to obtain lenient treatment on his own charges only if Jackson were convicted. In any event, it is clear under Morris, supra, 46 Cal.3d 1, that the absence of a “guarantee” to Mikles and McFarland that they would obtain a specified benefit as a result of their testimony provides no basis for relieving the prosecution of its obligation to correct the informants’ false and misleading testimony at trial.
Accordingly, we conclude that because the prosecution should have known of the false and misleading nature of the informants’ testimony, the prosecution was under a constitutional obligation to correct that testimony.
The question remains whether the prosecution’s failure to correct the informants’ false and misleading testimony was prejudicial with regard to the judgment as to guilt, the special circumstance findings, or the judgment as to penalty. In United States v. Agurs, supra, 427 U.S. 97, the United States Supreme Court explained that when the prosecution fails to correct testimony of a prosecution witness which it knows or should know is false and misleading, reversal is required “if there is any reasonable likelihood that the false testimony could have affected the judgment of the jury.” (Id. at p. 103 [49 L.Ed.2d at p. 349].) Accordingly, we apply this standard— which generally has been equated with the “harmless beyond a reasonable *598doubt” standard of Chapman v. California (1967) 386 U.S. 18 [17 L.Ed.2d 705, 87 S.Ct. 824, 24 A.L.R.3d 1065]10—to the facts of the present case.
With regard to the judgment as to defendant’s guilt of two counts of first degree murder and two counts of burglary, reversal clearly is not required. Defendant’s own admissions to the police unquestionably established his guilt of the two burglaries and the two first degree murders on a felony-murder theory, and the testimony of the numerous witnesses other than the jailhouse informants confirmed defendant’s admissions as to his complicity in each of the two separate incidents. Thus, with regard to the judgment as to guilt, there is no reasonable likelihood the false testimony of the jailhouse informants could have affected the jury’s verdict.
With regard to the special circumstance findings, defendant vigorously contends the error was prejudicial. As defendant points out, under the 1977 death penalty statute applicable in this case, both of the special circumstances at issue applied only in the event the trier of fact found the defendant “was personally present during the commission of the act or acts causing [Mrs. Ott’s] death, and with intent to cause death physically aided or committed such act or acts causing death . . . .” (Pen. Code, former § 190.2, subd. (c).) Defendant maintains that because the most detailed evidence concerning his role in the incident involving Mrs. Ott was provided by the two jailhouse informants, there is at least a reasonable likelihood that the prosecution’s failure to reveal and correct the informants’ false testimony could have affected the jury’s verdict as to the special circumstance findings. The referee agreed with defendant’s position on this point.
For a number of reasons, we disagree with the referee’s conclusion. First, defendant, in his own statement to the police, admitted personally participating in the beating of Mrs. Ott, acknowledging that he had hit her once *599when she was lying in her bed. Although defendant did not admit striking the blow or blows that actually caused Mrs. Ott’s death, the special circumstance was properly applicable to defendant even if he only “physically aided” the acts causing death, and his participation in the beating clearly satisfied that element since it helped to bring about the submission of the victim and rendered her less able to resist the attack. Furthermore, although defendant did not admit in his statement to the police that he acted with the intent to cause Mrs. Ott’s death, his statement did acknowledge that he knew when he participated in the brutal beating of the elderly Mrs. Ott that, only a few days earlier, the elderly Mrs. Curtis had died from a similar assault in which defendant also had participated. Thus, defendant’s own statement to the police went a long way toward proving the elements of the special circumstance allegations.
In addition, the testimony of defendant’s neighbors and acquaintances, recounting the numerous statements that defendant made to them shortly after the crimes, clearly established that defendant had the requisite culpability required by the special circumstance allegations. As noted above, the testimony of a neighbor indicated that when Mrs. Curtis was being carried out of the apartment house on a stretcher, defendant stood outside the building, smiled, laughed, and boasted to a neighbor that “he was the one who did that.” (Italics added.) Another acquaintance testified that when asked for an explanation of why he had committed the crimes, defendant stated that if Mrs. Curtis “had just been still—had been still and given him the money, that she would have been walking around today” (italics added), and that defendant had further described the two victims as “two old bags [who] were a nuisance and ... got what they deserved..” (Italics added.) Finally, defendant’s cousin testified that when defendant saw a newspaper article reporting the deaths of the two victims, he stated, “This is what / did, that it was because / needed some money.” (Italics added.)
In view of the strength of the evidence provided by defendant’s own statement to the police and by the numerous noninformant witnesses describing defendant’s statements and demeanor shortly after the crimes, we conclude there is no reasonable likelihood that the prosecution’s failure to correct the false testimony of the jailhouse informants could have affected the jury’s determination as to the special circumstance allegations.
Finally, defendant contends the error in question should be found prejudicial at least with regard to the judgment as to penalty. Defendant points out that (1) the only evidence the prosecution presented at the penalty phase related to the prosecution’s claim that defendant forcibly inserted a wine bottle into Mrs. Ott’s vagina, and (2) the jailhouse informants were the only *600witnesses who testified defendant had admitted committing such an act. Defendant maintains that because the jury’s decision to sentence defendant to death may have been influenced by the shocking and heinous nature of this incident, the prosecution’s failure to disclose and correct the jailhouse informants’ false testimony with regard to the inducements made to them requires that the death penalty be set aside and a new trial ordered as to penalty.
Again, we conclude that defendant’s claim of prejudice cannot be sustained. To begin with, although defendant seeks to isolate and highlight the incident involving the wine bottle as the principal factor motivating the jury to impose the death penalty, it is far more likely that defendant’s participation in two murders within a ten-day period, and his attitude and demeanor after the killings as reflected in his conduct and statements to his neighbors and acquaintances, played the key role in the jury’s decision as to penalty. As we have seen, numerous witnesses testified that defendant laughed and repeatedly bragged about his role in brutally beating to death the two vulnerable, elderly women, describing the victims as “two old bags [who] were a nuisance and . . . got what they deserved.” (Italics added.) The utter lack of remorse and extreme callousness demonstrated by defendant after the crimes could not help but weigh heavily in the minds of the jury in determining penalty.
Moreover, the jailhouse informants’ testimony was not the only evidence linking defendant to the wine bottle incident. When the police informed defendant, as they questioned him after the crime, that his fingerprints had been found in Mrs. Ott’s residence, defendant volunteered the information that he had touched a wine bottle on a table located next to Mrs. Ott’s bed. Although in his statement to the police defendant did not acknowledge having used the bottle to sexually assault Mrs. Ott, it is apparent the jury reasonably would have drawn that conclusion without reference to the jailhouse informants’ testimony, on the basis of the forensic evidence presented by the prosecution indicating that the wine bottle had been used in that fashion.
Thus, viewing the record as a whole, we conclude there is no reasonable likelihood the prosecution’s failure to disclose and correct the false testimony of the jailhouse informants with regard to the inducements offered them could have affected the jury’s penalty decision.
Accordingly, we conclude that defendant is not entitled to habeas corpus relief on this issue.
*601III. Alleged Incompetence of Counsel in Failing to Investigate the Jailhouse Informants
In addition to finding that the special circumstance findings should be set aside because of the prosecution’s failure to disclose the inducements offered to the informant witnesses, the referee also found that defendant’s trial counsel had failed to provide effective assistance of counsel with regard to the special circumstance allegations and that this failure constituted an independent ground for setting aside the special circumstance findings.
As we have explained in numerous cases following the United States Supreme Court’s decision in Strickland v. Washington (1984) 466 U.S. 668 [80 L.Ed.2d 674, 104 S.Ct. 2052]: “There are two components to a claim by a defendant that his counsel’s assistance was so defective as to require reversal of a conviction or death sentence. . . . ‘First, the defendant must show that counsel’s performance was deficient.’ . . . This requires a showing that ‘counsel’s representation fell below an objective standard of reasonableness.’ ... In evaluating a defendant’s showing of incompetence, we accord great deference to the tactical decisions of trial counsel. ‘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.’ ... [1] The second component requires that the defendant show prejudice resulting from counsel’s alleged deficiencies. ‘It is not enough for the defendant to show that the errors had some conceivable effect on the outcome of the proceeding. ... [1] The defendant must show that there is a reasonable probability that, but for counsel’s unprofessional errors, the result of the proceeding would have been different. A reasonable probability is a probability sufficient to undermine confidence in the outcome.’ ” (In re Marquez, supra, 1 Cal.4th 584, 602-603, citations omitted.) The Attorney General challenges the referee’s ineffective-assistance-of-counsel determination with regard to both of these components, asserting that trial counsel’s performance relating to the special circumstance allegations was not constitutionally deficient, and that, in any event, the requisite degree of prejudice was not established.
In determining that trial counsel provided constitutionally deficient representation with regard to the special circumstance allegations, the referee relied on evidence presented at the evidentiary hearing establishing that trial counsel failed to undertake any investigation of Mikles and McFarland in an attempt to discover evidence that might reveal the informants’ biases or motives to fabricate evidence, even though counsel was aware, several months before trial, of the prosecutor’s intent to call the informants as *602witnesses as to defendant’s guilt and as to the special circumstance allegations.
At the reference hearing, defendant’s trial counsel acknowledged that although the prosecutor had advised him informally well before trial of his intent to call Mikles and McFarland as witnesses, defense counsel intentionally had declined to conduct any investigation of the two informants. Defense counsel explained that although the prosecutor had notified him orally of his intent to call the two informants as witnesses, the prosecutor inadvertently had neglected to include the two informants on a witness list provided to the defense. Defense counsel testified as to his belief that if he could truthfully represent to the trial court that he had failed to undertake any investigation of the informants, the trial court might view his inaction as “detrimental reliance” on the incomplete witness list and might grant a pretrial motion to preclude the two prosecution witnesses from testifying at trial.
Defense counsel did make such a motion at the outset of trial, but the trial court denied the motion when it was disclosed that the defense had actual notice well in advance of trial that the prosecutor planned to call the two informants as witnesses. The court stated that, if necessary, it would grant defense counsel a continuance and funds for an investigator, but there is no indication that defense counsel ever followed up with an investigation at that late date.
The referee, although recognizing the apparent tactical nature of defense counsel’s decision not to undertake any pretrial investigation of Mikles or McFarland, found that no reasonably competent criminal defense attorney would have made such a decision. The referee explained: “In light of the crucial nature of the testimony of Mikles and McFarland on the special circumstance allegations, and the obviously inadvertent nature of the prosecutor’s omission of their names from the witness list furnished [to defense counsel], and the failure of [defense counsel] to seek formal discovery from the prosecution, it is the Referee’s conclusion that no reasonably competent and experienced criminal defense lawyer would consider this failure to investigate a reasonable tactical decision.”
In turning to the question whether counsel’s deficient performance was prejudicial under the Strickland standard with regard to the special circumstance findings, the referee recognized that in this context the prejudice question involved two subsidiary inquiries: (1) what information would a reasonable investigation of the informants have revealed?, and (2) what effect would such information likely have had on the jury’s determination?
*603On the first point, the referee found on the basis of the evidence presented at the hearing that a reasonable investigation of the jailhouse informants would have disclosed a variety of evidence that would have been helpful to the defense in impeaching the informants’ testimony. First, the referee found that such an investigation would have disclosed the inducements, discussed above, that had been sought by, and offered to, both informants in return for their testimony against defendant. Second, the referee found that an investigation of Mikles’s background would have revealed that he was a former member of the Aryan Brotherhood, a White supremacist prison organization, information that could have been useful in demonstrating Mikles’s possible bias against defendant, who is Black. This information also might have raised possible doubts as to the veracity of Mikles’s general claim that defendant had confided in him and the veracity of Mikles’s specific testimony that defendant had made a racist comment concerning the victims in this case. (See, ante, p. 588, fn. 5.) Finally, the referee found that an investigation would have disclosed that the two informants were acquainted with one another and that each was a “trusty” in the same section of the jail and was aware, prior to defendant’s trial, that the other inmate was to testify at that trial. The referee indicated this information would have been useful to demonstrate that the informants had the opportunity to collaborate on their testimony so as to ensure consistency and thereby improve their chances of obtaining the benefits they hoped to receive from law enforcement officers.
With respect to the second point, the referee expressed the view that had information been presented to the jury that would have been disclosed by a proper investigation, “[i]t is reasonable to conclude that the jury would have rejected [the informants’] testimony as false and unbelievable, and found that the prosecution had not proven the special circumstance allegations.” The referee stated in this regard: “Having listened to their testimony and observed their demeanor at the Reference Hearing, it is the Referee’s conclusion that, had the impeachment evidence been presented at petitioner-defendant Jackson’s trial, the jury in all likelihood, would have considered the testimony of McFarland and Mildes as being untrue, with the remaining evidence of the prosecution insufficient to sustain the special circumstance allegations.”
The Attorney General takes issue with each of the referee’s findings related to this claim. First, the Attorney General maintains that defense counsel’s decision not to undertake any investigation of the informants’ backgrounds, while ultimately unsuccessful, was not constitutionally deficient. The Attorney General acknowledges that although courts generally are reluctant to second guess the tactical decisions of counsel, such decisions are not totally immune from scrutiny and may fall below a constitutionally *604minimal standard of competence. (See, e.g., People v. Frierson (1979) 25 Cal.3d 142,166 [158 Cal.Rptr. 281, 599 P.2d 587].) He argues, however, that the referee erred in finding that counsel’s action fell into the latter category.
Additionally, the Attorney General challenges the referee’s conclusions on both points relating to the issue of prejudice. With respect to the question what information would have been uncovered by a reasonable investigation, the Attorney General maintains that (1) defense counsel, a former deputy district attorney in Long Beach, knew at the time of trial that when an informant would cooperate in an investigation, it was the general practice for prosecutors to provide information regarding such cooperation to the judges handling any cases involving the informant, and there is no evidence that a reasonable investigation would have provided defense counsel with additional information, (2) no evidence was presented demonstrating how defense counsel would have learned of Mikles’s membership in the Aryan Brotherhood, and (3) it was unlikely a reasonable investigation would have revealed that Mikles and McFarland had collaborated on their testimony, because neither informant was likely to have cooperated in any such investigation. With respect to the question of the likely effect on the jury’s special circumstance findings, the Attorney General argues that (1) any additional information that an investigation might have uncovered was unlikely to have altered the jury’s assessment of the informants’ testimony, and (2) in any event, even if the jury were to discount the informants’ testimony, there is no reasonable probability that the jury would have arrived at a different conclusion on the special circumstance allegations in view of the testimony provided by the noninformant witnesses.
We conclude there is no need to determine whether counsel’s failure to investigate the background of the jailhouse informants was constitutionally deficient, because we have determined that the ineffective assistance claim can be resolved solely on the basis of the prejudice prong of the Strickland test. As the United States Supreme Court explained in Strickland v. Washington, supra, 466 U.S. 668, 697 [80 L.Ed.2d 674, 699-700], “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 . . . . 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.”
To prevail on an ineffective-assistance-of-counsel claim, a defendant must demonstrate a significantly greater likelihood of prejudice than a defendant is required to prove in order to prevail when the prosecution has failed to correct perjured testimony: the defendant must establish that there *605is “a reasonable probability” that the error “would have” affected the judgment (see Strickland v. Washington, supra, 466 U.S. 668, 694 [80 L.Ed.2d 674, 697-698]), rather than simply that there is “any reasonable likelihood” that the error “could have” affected the result (see United States v. Agurs, supra, 427 U.S. 97, 103 [49 L.Ed.2d 342, 349-350]). In the preceding section of the opinion, we have concluded that the prosecution’s failure to correct the informants’ false and misleading testimony was not prejudicial under the “any reasonable likelihood” standard. In light of that conclusion, we conclude that defendant similarly has failed to demonstrate reversible error with regard to the ineffective-assistance-of-counsel claim.
It is true the referee found that defense counsel’s assertedly deficient investigation resulted not only in the absence of evidence concerning the informants’ false and misleading testimony with regard to inducements, but also in the failure to discover evidence of Mikles’s former membership in the Aryan Brotherhood and of the opportunity for collaboration between Mi kies and McFarland. Assuming, without deciding, that this evidence would have been discovered by a reasonable investigation and would have been admissible as additional impeachment material at trial,11 counsel’s alleged failing still would not have been prejudicial. As we already have explained, we have concluded in view of the strength of the prosecution’s case based on the evidence other than the testimony of the jailhouse informants, that there is “no reasonable likelihood” the jury’s determination of guilt, special circumstances, or penalty “could have” been affected by the revelation that the informants actually had lied on the witness stand. For the same reasons, we conclude that even taking into consideration the additional evidence that might have been introduced to impeach the informants, prejudice has not been demonstrated under the more demanding prejudice standard applicable to the ineffective-assistance-of-counsel claim.
Accordingly, we conclude that defendant has failed to establish sufficient prejudice to warrant reversal of the special circumstance findings, or of the penalty verdict, based on trial counsel’s failure to conduct an investigation with regard to the jailhouse informants.
IV. Alleged Incompetence of Counsel in Failing to Investigate and Present Mitigating Evidence With Regard to the Circumstances of Defendant’s Childhood
On appeal and in an earlier habeas corpus petition which accompanied the appeal, defendant contended he had been deprived of his constitutional right *606to the effective assistance of counsel at the penalty phase of his trial because defense counsel failed to call any mitigating witnesses on his behalf. In Jackson I, supra, 28 Cal.3d 264, 293-295, we rejected this claim on the ground that defendant had “failed to demonstrate (by his petition for habeas corpus or otherwise) what mitigating evidence, if any” was available to his trial counsel. On that basis, the Jackson I court distinguished our then-recent decision in People v. Frierson, supra, 25 Cal.3d 142, 164-166, where we reversed on similar grounds a judgment as to penalty, because the habeas corpus petition contained declarations from various witnesses revealing the mitigating evidence they would have provided on the defendant’s behalf. We concluded instead, in Jackson I, that the controlling authority was People v. Durham (1969) 70 Cal.2d 171, 191-192 [74 Cal.Rptr. 262, 449 P.2d 198], where we refused to overturn a judgment as to penalty in the absence of a showing of the mitigating evidence that would have been presented but for trial counsel’s allegedly ineffective representation. (Jackson I, supra, 28 Cal.3d at pp. 293-295.) Although one of the dissenting opinions in Jackson I took the position that the record before the court was sufficient to establish there was at least one witness who could have been called by defense counsel—defendant’s elderly grandmother, Mattie Jackson, who had attended the trial daily (see id. at pp. 325-326 (dis. opn. by Mosk, J.))—the majority opinion in Jackson I found that defense counsel had a reasonable tactical basis for not calling Mrs. Jackson as a witness: defense counsel believed she was senile and might prove to be a liability rather than an asset to defendant, because she insisted (despite defendant’s own confession) that defendant was totally innocent of the crimes. (Id. at p. 295.)
Defendant then filed the present habeas corpus proceeding in which, among other contentions, he renewed his claim of ineffective assistance at the penalty phase, supporting that claim with declarations from a substantial number of family members disclosing the mitigating evidence they assertedly would have provided had they been called as witnesses at the penalty phase. We issued an order to show cause and directed that the referee take evidence and make findings with regard to this claim.
At the evidentiary hearing, the defense presented evidence from five members of defendant’s family (in addition to Mattie Jackson), who testified consistently to the very difficult, and often abusive, circumstances of defendant’s young childhood, and who indicated they would have testified on defendant’s behalf at the penalty phase had defendant’s trial counsel so requested. We summarize the testimony of the witnesses as it relates to defendant’s childhood.
(1) Defendant’s father, Alfred Jackson, testified that when defendant was a very young infant, living in Arkansas, he cried all the time; as a result, his *607mother was always angry with him and, according to their landlady, his mother frequently “whoop[ed]” him. As an infant, defendant had a bowel problem that required surgery; after the surgery the doctor who performed the operation kept defendant in the doctor’s own home for four months because the doctor believed defendant was being abused. Defendant’s mother wanted the doctor to keep defendant permanently, but because defendant’s father wanted his son back, defendant was returned to the family home. Shortly thereafter, when defendant was nine months of age, defendant’s mother and father “tore up” their apartment in a fight which took place in defendant’s presence, after which defendant’s mother said she did not wish to live with either defendant or defendant’s father.
Defendant’s father then took defendant to live with Mattie Jackson, defendant’s paternal grandmother, and defendant lived there for the next four years. Although defendant’s mother lived only 40 miles away, she rarely visited defendant. One day, however, defendant’s mother unexpectedly appeared and took defendant away. Two months later, a police officer notified defendant’s father that defendant’s mother had left defendant with a woman in Ohio and had not come back for him for fifteen days.
Shortly thereafter, defendant’s mother remarried, and defendant went to live in the Watts section of Los Angeles with his mother and her new husband, Robert Hackworth, Sr. Defendant’s father testified that he visited his son in Los Angeles when defendant was approximately six years of age. At the time, defendant had sores on his head from some kind of hair-straightening chemical that his mother had applied. In addition, defendant had a two-inch-long scab on his hand which defendant said had resulted from a beating inflicted by his stepfather.
(2) Defendant’s aunt, Freddie Mae Hall, also testified that after defendant was born, defendant’s mother and father did not get along, and because defendant’s mother did not wish to take care of defendant, he went to live with his grandmother from the age of nine months until he was five years of age. When defendant reached that age, he went to live with his mother and her new husband, residing with them for two or three years, until defendant’s mother began bringing defendant to Mrs. Hall and asking her to take him in for varying periods of time, ranging from two weeks to two months. Mrs. Hall testified that defendant’s mother told her that she (defendant’s mother) and defendant’s stepfather fought a lot, and that although defendant’s stepfather paid attention to his own son, Robert Hackworth, Jr., the stepfather did not like defendant and did not wish him to reside in the family home.
Mrs. Hall stated that defendant appeared happy while at her house and liked to play with her daughter, but that just when he would begin to adjust *608to being in her home, his mother would return without notice and take him away. Mrs. Hall stated she never enrolled defendant in school because he was never with her for a long enough period of time. She recalled that on one occasion, defendant’s father paid to enroll him in a military school and bought him new school clothes, but on the day the clothes were purchased defendant’s mother showed up unexpectedly and forcibly took defendant home with her. Mrs. Hall said defendant was “hollering” he did not want to go home with his mother, and told Mrs. Hall he was terrified of going there because his stepfather beat him unmercifully for no reason at all.
Mrs. Hall recounted another incident that occurred when she visited defendant at his mother’s home when he was eight years of age. She testified that on this occasion, the house smelled like human flesh, and she observed skin peeling off the face and neck of defendant’s stepfather. Defendant’s mother explained she had had an argument with her husband and had thrown hot water on him. Defendant, who had been present during the encounter, was cowering in the back room. At that time there were red sores on defendant’s head, and his mother stated she had burned it while using a homemade solution to straighten his hair.
(3) Defendant’s uncle by marriage, John Hall (Freddie Mae Hall’s husband), testified he had accompanied his wife on the visit to defendant’s mother’s home when defendant was eight years of age. He testified the two-room apartment was filthy; roaches were running all over, and there were rat droppings by the door. Defendant’s stepfather was pulling dead skin off his face, and defendant was cowering in a corner of the back room, crying, shaking, and appearing very frightened. Mr. Hall gave defendant some money, and defendant’s stepfather allowed defendant to take his younger half-brother to a nearby store to make a purchase. When the boys returned, however, defendant’s stepfather slapped defendant, stating, “I told you not to get this, boy, you can’t do nothing right.” Defendant’s mother did not intervene.
Mr. Hall also testified that when defendant was eight or nine years of age, defendant hitchhiked to Mr. and Mrs. Hall’s home in Long Beach, telling Mr. Hall defendant’s stepfather had been beating him up and he could not stand it anymore. Defendant stayed with the Halls until his mother found out where he was and took him back home. Mr. Hall said defendant was happy at the Halls but was also confused, because he never knew when his mother was going to come to take him away.
Finally, Mr. Hall testified defendant’s stepfather always treated his own natural son differently from defendant. Although the stepfather showed love *609to his own child, he used angry, cursing language when speaking to defendant.
(4) Another of defendant’s paternal aunts, Lucy Mae Trotter, testified that when she lived with defendant at his grandmother’s house, he was a good little boy. She also testified that subsequently, when defendant was approximately seven years of age and living with his mother and stepfather, defendant’s mother called and told her defendant’s stepfather was “beating up” on defendant and had put him in the hospital. Ms. Trotter said defendant’s mother told her that defendant’s stepfather would beat him in order to take money which defendant had earned or in order to force defendant to obtain a job.
(5) Defendant’s half brother, Robert Hackworth, Jr., who was three years younger than defendant, testified that their mother “wasn’t too up to par,” and, for example, would tell the boys that persons were coming to the house to kill them, and then would run out of the house and leave the boys alone.
He also confirmed the testimony of the other witnesses that his father (defendant’s stepfather) repeatedly abused defendant. Defendant’s half brother described one incident, when defendant was approximately eight or nine years of age, in which defendant attempted to intervene in a fight between his mother and his stepfather. Defendant’s stepfather hit defendant on the head with a bottle, sending him to the hospital. On another occasion in which defendant attempted to break up a fight between his mother and his stepfather, his stepfather hit him on the side with a board, again hospitalizing defendant.
Finally, defendant’s half brother testified that, in general, his father treated him much differently from defendant. Although his father often would give him things, the father would give little to defendant. Defendant’s half brother testified that although he felt he was loved in the home, defendant was treated “like a dog.”
The referee found that had defendant’s trial counsel conducted a reasonable investigation of potential mitigating evidence for the penalty phase, he would have discovered all of the above witnesses. The referee further indicated that, in his view, had the witnesses testified at the penalty phase, “[i]t is reasonably probable that . . . the mitigating evidence would have evoked the response in the jury to give [defendant] a life sentence rather than the death penalty.”
The Attorney General acknowledges that a reasonable investigation of potential mitigating evidence for the penalty phase would have *610disclosed the above witnesses who testified in defendant’s behalf at the evidentiary hearing: they were close relatives of defendant who either were already known to defense counsel (Alfred Jackson and Freddie Mae Hall) or readily could have been discovered. The Attorney General maintains, however, that the referee’s conclusion nonetheless is erroneous on three separate grounds. First, he asserts that defense counsel’s testimony at the reference hearing demonstrated that counsel had a reasonable tactical basis for declining to undertake an investigation into defendant’s childhood, and thus that counsel’s representation was not constitutionally deficient. Second, he contends that even if counsel should have conducted such an investigation and should have discovered the foregoing evidence of defendant’s difficult childhood, defense counsel’s testimony at the reference hearing indicates that, for tactical reasons, counsel still would not have introduced that evidence at the penalty phase. The Attorney General maintains that, in view of the state of the law at the time of trial, the failure to introduce such evidence would not have been constitutionally deficient. Third, the Attorney General argues that even if the mitigating evidence that was disclosed at the evidentiary hearing had been introduced at the penalty phase, there is no reasonable probability that the penalty verdict would have been different in light of the nature of the crimes at issue in this case and defendant’s attitude concerning the crimes as revealed by his almost-contemporaneous statements to neighbors and acquaintances.
As noted, the referee’s resolution of mixed questions of law and fact is subject to independent review by this court. (In re Marquez, supra, 1 Cal.4th 584, 603.) “ ‘Mixed questions [in the context of a claim of ineffective assistance of counsel] “include the ultimate issue, whether assistance was ineffective, and its components, whether counsel’s performance was inadequate and whether such inadequacy prejudiced the defense.” ’ ” (Ibid.)
In undertaking our independent review, we turn first to the question whether counsel’s representation was deficient, i.e., whether it “fell below an objective standard of reasonableness.” (Strickland v. Washington, supra, 466 U.S. 668, 688 [80 L.Ed.2d 674, 693-694].) As explained above, “[i]n evaluating a defendant’s showing of incompetence, we accord great deference to the tactical decisions of trial counsel. ‘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.’ [Citation.]” (In re Marquez, supra, 1 Cal.4th 584, 603, italics added.)
At the reference hearing, defendant’s trial counsel testified he was aware at the time of trial, from conversations with defendant’s father and *611defendant’s grandmother, that defendant had had a difficult childhood and may have been abused, but that he (trial counsel) decided, for tactical reasons, not to conduct an investigation of defendant’s background or to present any mitigating evidence at the penalty phase. Counsel explained that he made the decision not to present any mitigating evidence so as to keep from the jury evidence of prior violent conduct committed by defendant, specifically evidence that in 1976, one year before the crimes here at issue, defendant had punched two young women in the face with a closed fist. The trial court had ruled that the prosecution would be precluded from introducing this evidence in its case-in-chief at the penalty phase because the prosecution had failed to give defendant timely notice of its intent to introduce such evidence at the penalty phase (see Pen. Code, § 190.3, j[ 4), and defense counsel explained he believed that were he to present any evidence in mitigation, there was a risk the trial court would permit the prosecution to introduce this evidence of defendant’s prior violent conduct in rebuttal.
Defendant’s trial counsel indicated his strategy at the penalty phase was to emphasize to the jury the inconclusiveness of the evidence that defendant, rather than one or more of his accomplices, had played the primary role in beating the two elderly women so brutally, and counsel stated his belief that the damage to defendant’s case that would result in the event evidence of defendant’s prior violent conduct were admitted at the penalty phase outweighed any benefit defendant might receive from having his family testify in his behalf. In response to a question from defendant’s counsel in the habeas corpus proceedings, defendant’s trial counsel stated he had made a tactical decision not to call any witnesses at the penalty phase “regardless of how many family members that [he] could have found to come to court and testify at the penalty phase, and regardless of how compelling their testimony was concerning [defendant’s] extremely bad experiences as a child.”
The referee found that trial counsel’s tactical decision not to conduct an investigation of defendant’s background and not to present any mitigating evidence “cannot be considered a reasonable decision” under prevailing professional standards. Suggesting that counsel’s tactical decision was based on a misconception concerning the proper scope of rebuttal evidence, the referee found that counsel failed to appreciate that mitigating evidence relating to the abusive treatment defendant received as a child could have been introduced by the defense without opening the door for the prosecution’s introduction of evidence of defendant’s prior violent conduct. Furthermore, the referee suggested that even if defendant’s trial counsel had doubts as to whether the introduction of particular mitigating evidence would open the door for the introduction of evidence of defendant’s prior violent conduct *612in rebuttal, defense counsel’s course of conduct was an unreasonable one because he could have requested an in limine hearing under Evidence Code section 402 and obtained an advance ruling on the evidentiary question.
The Attorney General maintains initially that defense counsel’s failure to undertake an investigation of defendant’s childhood may be sustained as a reasonable tactical decision, but on this point we agree with the referee’s determination. As we explained in our recent decision in In re Marquez, supra, 1 Cal.4th 584, 606: “In some cases, counsel may reasonably decide not to put on mitigating evidence, but to make that decision counsel must understand what mitigating evidence is available. . . .” Here, counsel testified that he decided that evidence of defendant’s prior violent conduct, which he believed would be admissible in rebuttal, would outweigh any mitigating evidence, but he made that determination without conducting any investigation to discover what mitigating evidence was available. As in Marquez, “[counsel’s] decision not to find out. . . cannot be supported as a tactical choice.” (Ibid.)
Thus, we conclude that defendant’s trial counsel, by failing to conduct a reasonable investigation of defendant’s background and childhood to enable him to make an informed decision as to the best manner of proceeding at the penalty phase, failed to provide competent representation under the prevailing professional standards.
The question of prejudice remains. As we already have noted, the Attorney General concedes that had defendant’s trial counsel conducted a reasonable investigation of defendant’s childhood, he would have discovered the evidence of childhood abuse that appellate counsel presented at the reference hearing. The Attorney General maintains, however, that the testimony of defendant’s trial counsel at the reference hearing makes it clear that even had counsel conducted such an investigation and discovered all of the foregoing evidence, trial counsel, for tactical reasons, would not have introduced this evidence at the penalty phase. The Attorney General argues that under these circumstances, there is no reasonable probability that defense counsel’s failure to investigate defendant’s background affected the jury’s penalty determination, because the penalty phase would have been conducted in exactly the same manner in the event trial counsel had conducted such an investigation.
Defendant acknowledges that his trial counsel’s testimony at the reference hearing indicates that counsel would not have called any of defendant’s relatives as witnesses at the penalty phase, even had counsel learned the details of their potential testimony through a more complete investigation. *613Defendant maintains, however, that if his trial counsel, after conducting an investigation and discovering the evidence of childhood abuse defendant had suffered, for tactical reasons had refrained from introducing that evidence at the penalty phase, counsel’s decision not to introduce the mitigating evidence would itself have constituted constitutionally deficient representation, and thus cannot properly serve as a basis for finding that counsel’s failure to investigate was nonprejudicial.
The Attorney General does not suggest that defense counsel’s testimony, that he would not have introduced the mitigating evidence, would render harmless counsel’s initial failure to investigate if the failure to introduce such evidence would itself amount to constitutionally deficient representation. The Attorney General argues, however, that had counsel declined to introduce the mitigating evidence for the tactical reason disclosed at the reference hearing, counsel’s representation would not have fallen below an objective standard of reasonableness and would not have been constitutionally deficient.
Thus, as part of the prejudice determination in this case, we must determine whether counsel’s representation would have been constitutionally deficient if, for the tactical purpose expressed at the reference hearing, counsel had refrained from introducing the evidence that would have been discovered by a reasonable investigation.
In defending the reasonableness of counsel’s tactical determination not to introduce such evidence, the Attorney General initially takes issue with the referee’s legal conclusion as to the proper scope of rebuttal evidence at the penalty phase. The Attorney General argues that, contrary to the referee’s conclusion, the prosecution properly could have introduced evidence of defendant’s prior acts of violence on rebuttal, had defendant’s family members testified concerning the physical and psychological abuse inflicted upon defendant when he was a child. In People v. Ramirez (1990) 50 Cal.3d 1158, 1191-1193 [270 Cal.Rptr. 286, 791 P.2d 965], however, we concluded that the trial court in that capital proceeding had erred in permitting the prosecution at the penalty phase to introduce evidence of the defendant’s prior misconduct in response to testimony by the defendant’s mother disclosing the adverse circumstances experienced by the defendant in his early childhood. In Ramirez, we explained that under the limits on rebuttal evidence recognized in this court’s earlier decision in People v. Rodriguez (1986) 42 Cal.3d 730, 792, footnote 24 [230 Cal.Rptr. 667, 726 P.2d 113], the prosecution is not permitted to go beyond the aspects of the defendant’s background on which the defendant has introduced evidence. Thus, when a defendant confines his mitigating evidence to the adverse circumstances of *614his childhood, the prosecution may not “introduce evidence of a course of misconduct that defendant had engaged in throughout his teenage years that did not relate to the mitigating evidence” presented by defendant. (Ramirez, supra, 50 Cal.3d at p. 1193.) Therefore, under the current governing case law, it is now clear that the referee was correct in concluding that defendant’s trial counsel could have introduced evidence of defendant’s abused childhood without opening the door to the prosecution’s introduction of evidence of defendant’s prior violent assault.
Although defense counsel’s understanding of the scope of rebuttal evidence presently can be characterized as mistaken, such an error, in itself, would not necessarily demonstrate that counsel’s performance was constitutionally deficient. The trial in this case preceded the decisions in Rodriguez, supra, 42 Cal.3d 730, and Ramirez, supra, 50 Cal.3d 1158, by many years. Although these decisions applied to the penalty phase of a capital proceeding the preexisting, generally applicable limits on rebuttal evidence, we are aware from our familiarity with the trials conducted in Rodriguez, Ramirez, and other capital cases (see, e.g., People v. Miranda (1987) 44 Cal.3d 57, 119-122 [241 Cal.Rptr. 594, 744 P.2d 1127]) that, before this court specifically addressed and resolved this issue in our Rodriguez and Ramirez decisions, the applicability of the limits on rebuttal evidence to the unusual evidentiary material admissible at the penalty phase of a capital trial was a frequent source of uncertainty for both trial counsel and trial courts. When we eliminate, as we must, the potentially distorting effects of hindsight (see Strickland v. Washington, supra, 466 U.S. 668, 689 [80 L.Ed.2d 674, 694-695]), we conclude that the confusion of defendant’s trial counsel on this legal question at the time of defendant’s trial was not so unreasonable as to demonstrate that a tactical decision not to offer this evidence (or to request a hearing under Evid. Code, § 402), based on such a mistake, would have fallen below the level of constitutionally adequate representation.
Defendant further contends that even if trial counsel’s concern, that introduction of the mitigating evidence would open the door to admission of the prosecution’s evidence of defendant’s prior violent criminal activity, was not unreasonable when viewed from counsel’s perspective at the time of trial, a tactical decision not to present the mitigating evidence nonetheless would fall below a standard of objective reasonableness because such a decision would leave the jury without any mitigating evidence to consider on defendant’s behalf. Although mitigating evidence concerning the circumstances of a defendant’s childhood and background often is of crucial importance at the penalty phase, providing information through which the jury can make an “individualized” determination as to the appropriate sentence (see In re Marquez, supra, 1 Cal.4th 584, 607-609), defense counsel, in determining whether to present such information, properly may take *615into account the detrimental consequences that may result from the introduction of such evidence, including the nature of the evidence that the prosecution may elicit either on cross-examination of the proposed defense witnesses or on rebuttal. (See, e.g., People v. Miranda, supra, 44 Cal.3d 57, 120-122.)
In this case, defendant’s trial counsel explained at the reference hearing why he placed such a high priority on keeping the prosecution from bringing before the jury, either on cross-examination of defendant’s relatives or on rebuttal, the fact that defendant previously had committed violent assaults on two women, repeatedly striking one in the face with his fist. Counsel believed that defendant’s best chance to avoid the death penalty rested on the argument that the jury at least should entertain a “lingering doubt” as to defendant’s role in the underlying offenses, because, in counsel’s view, the evidence did not rule out the possibility that one or more of defendant’s accomplices in the capital crimes had inflicted the bulk of the injuries on the victims. Counsel had relied on a similar argument in urging that the jury reject the special circumstance allegations, and, although the argument had proved unsuccessful in that setting, counsel believed the jury might entertain enough of a “lingering doubt” on this point to lead it to reject a death sentence. Counsel felt that if the jury were to learn that defendant had, on an earlier occasion, personally engaged in similar violent assaults on two women and repeatedly had punched one of the women in the face with a closed fist, any remaining doubt as to defendant’s personal responsibility for the beating deaths of the two elderly victims would have been eliminated.
The transcript of defendant’s trial reveals that in his closing argument at the penalty phase—an argument which we found “reasonable” in Jackson I, supra, 28 Cal.3d 264, 295—defense counsel did, in fact, advance this lingering-doubt argument, maintaining that from the evidence the jury could not know “the degree of participation” of each of the young men who together had engaged in the crimes. Although another attorney reasonably might have made a different tactical decision, we cannot say that defense counsel’s tactics rendered his representation constitutionally deficient. As we have explained, in this context it is appropriate to “accord great deference to the tactical decisions of trial counsel” (In re Marquez, supra, 1 Cal.4th 584, 603), and to make every effort to avoid second-guessing counsel on the basis of hindsight.
Accordingly, we conclude that although defense counsel should have conducted a reasonable investigation of defendant’s childhood, defendant has failed to demonstrate the existence of a reasonable probability that counsel’s failure to do so affected the penalty determination.
*616V. Conclusion
We summarize our conclusions on the issues presented in this proceeding.
1. We conclude that defendant has failed to establish that his admissions to the jailhouse informants were elicited by law enforcement officers in violation of United States v. Henry, supra, 447 U.S. 264.
2. We conclude that defendant has established that law enforcement officers offered inducements to the jailhouse informants for their testimony at defendant’s trial and that the prosecution failed to correct the informants’ false and misleading testimony with regard to such inducements. On the question of prejudice, however, we conclude that the constitutional error was not prejudicial with regard to the judgment as to guilt, the special circumstance findings, or the judgment as to penalty.
3. We conclude there is no need to determine whether defendant’s trial counsel provided deficient representation with regard to the special circumstance allegations, because in any event counsel’s failings in this regard were not prejudicial.
4. We conclude defendant has established that his trial counsel provided deficient representation in failing to investigate the availability of mitigating evidence with regard to defendant’s childhood. We also conclude, however, that counsel’s failure to investigate was not prejudicial in this case, because had counsel conducted such an investigation and discovered the evidence that ultimately was presented at the reference hearing, counsel nonetheless would have refrained, for tactical reasons, from introducing such evidence at the penalty phase. Contrary to defendant’s contention, such a tactical decision would not have constituted deficient representation. Accordingly, there is no reasonable probability that the judgment as to penalty was affected by counsel’s failure to conduct such an investigation.
The order to show cause, issued November 27,1981, in this proceeding, is discharged, and the petition for writ of habeas corpus is denied.
Lucas, C. J., Panelli, J., Arabian, J., and Baxter, J., concurred.
The inquiry on the Henry issue was prompted by a declaration signed by McFarland, submitted with the habeas petition, in which McFarland declared that a member of the sheriff’s department had instructed him to listen carefully and report all conversations with fellow inmates. At the reference hearing, however, McFarland recanted the statements in his declaration and testified that he had signed the declaration at the request of another inmate after being stabbed. In addition, both McFarland and Mikles testified at the reference hearing that all their conversations with Jackson took place before the two inmates had any contact with law enforcement officers concerning the statements, and a deputy sheriff who was in charge of the men’s central jail in Los Angeles testified that the sheriff’s department had a policy not to place inmates for the purpose of eliciting incriminating statements. On the basis of this evidence, the referee found that law enforcement officers at no time, advised McFarland or Mikles to listen to jail inmates and, thus, that the admission of the jailhouse statements allegedly made by defendant to McFarland and Mikles did not violate the principles enunciated in Henry. As noted, defendant does not challenge this finding.
Defendant’s habeas corpus petition raised numerous claims in addition to those on which we ordered a reference hearing. Although our initial order to show cause did not specify the claims as to which we found a prima facie case to have been stated, the parties have confined their briefing and arguments to the issues we referred to the referee. We now specifically deny habeas corpus relief with regard to all claims not explicitly addressed in our opinion.
The following claims are denied on the ground they were raised and rejected on appeal (see In re Waltreus (1965) 62 Cal.2d 218, 225 [397 P.2d 1001]): defendant’s claims that (1) he was denied effective assistance of counsel at trial because of counsel’s (i) failure to properly investigate and prepare the case for trial, (ii) failure to prepare and present the defense of diminished capacity based on marijuana intoxication, (iii) failure to pursue formal or informal discovery procedures, (iv) ignorance of basic criminal procedure, (v) failure to bring a motion to exclude Mikles’s testimony regarding defendant’s confession, (vi) failure to make proper motions and objections, and (vii) argument against his client at both the guilt and penalty phases; (2) the trial court erred in refusing to appoint a second attorney to represent defendant; (3) defendant’s confessions were elicited in violation of his federal constitutional rights under Miranda v. Arizona (1966) 384 U.S. 436 [16 L.Ed.2d 694, 86 S.Ct. 1602, 10 A.L.R.3d 974]; (4) the prosecutor committed prejudicial misconduct in requesting that defendant testify in the presence of the jury; (5) defendant was denied due process of law by the prosecution’s use of a previously undisclosed confession made to Mikles; (6) defendant was denied his right to be present in court during proceedings on his motion for mistrial; (7) the trial court erred in admitting the former testimony of two prosecution witnesses; (8) defense counsel’s submission of the penalty phase upon the evidence adduced at the guilt phase was tantamount to a stipulated judgment of death; and (9) the 1977 death penalty law violates both the federal and state constitutional proscriptions against cruel and unusual punishment.
The following claims are denied on the ground they could have and should have been raised on appeal (see In re Terry (1971) 4 Cal.3d 911, 927 [95 Cal.Rptr. 31, 484 P.2d 1375]; In re Dixon (1953) 41 Cal.2d 756, 759 [264 P.2d 513]): defendant’s claims that (1) defendant was denied his state and federal constitutional right to trial by jury, by the exclusion of jurors from the guilt phase because of their opposition to capital punishment; (2) the trial court erroneously excluded five jurors for cause; (3) the prosecutor systematically excluded Black jurors from the jury panel through the exercise of peremptory challenges; and (4) the trial court erred in instructing the jury concerning the felony-murder rule.
Defendant’s claim that he was denied his state and federal constitutional rights on the ground that his case was arbitrarily and capriciously selected for the death penalty is denied on the merits. (See McClesky v. Kemp (1987) 481 U.S. 279 [95 L.Ed.2d 262, 107 S.Ct. 1756].)
On cross-examination, Gaines’s credibility was somewhat impeached when she acknowledged that at the time of the offenses, she had been living with Elton Boyd, who participated with defendant in the burglary of Mrs. Curtis’s apartment and who, in a separate trial, had been convicted of the murder of Mrs. Curtis. The questioning raised the possibility that Gaines may have been biased against defendant because defendant had informed the police of Boyd’s participation in the Curtis offense.
Mikles’s testimony was the more detailed of the two. His account of his principal conversation with defendant was as follows:
“We were waiting to go back to the county jail, and I come over and I sat next to him. And I just went up and I asked him—I said, ‘You had a couple of hot murder cases, a couple of 187’s?’
“He said, ‘Yeah.’
“I says, ‘How do you pick up a couple—a couple murders in a robbery or something?’
“He said, ‘No. I had a burglary.’
“I tell him, ‘How do you turn ... a burglary into a murder?’
“He said, ‘Oh, . . . me and a couple of my partners, you know, we were out going to do this burglary in this apartment complex and we all went in and we were ransacking the house.’
“He was in—he was in the living room, wrapping up the TV. I remember him telling me something about wrapping up a TV wire or something like that, and this old lady comes up in the hallway, and I guess he caught her attention or something, you know, or she might have made some noise. I can’t really remember exactly what caused his attention about it, you know. I can’t foresee anything catching my attention when I am ransacking a house, but he went over and he hit her a couple of times, and I guess she was backing up into the bedroom, and he kept firing on her until she—he knocked her out on the bed.
“So they kept—they were going through the house, and a youngster—I guess there was a youngster, a juvenile or something. I remember, you know, he was telling me one of the guys he sent outside to keep watch, because they were in the pad too long. So he is going—he is in the bedroom, and the lady is making noise. She is waking up. She is screaming or something, so he beats on her a couple of more times you know. How many times I really couldn’t say, till he knocked—till what it appeared, he knocked her out again. She fell down on the bed. So I wasn’t really getting on his case.
“I asked him the question, you know, ‘Why, you know, because she was, you know—she was so old—why pounce on her so much?’
“And he said that when she woke up, you know, he just went off. It just pissed him off so bad, because—because he sick—he beat on her to the point, when he knocked her out again, he told me that he was so hot at her that there was a bottle on the stand next to the bed and he took the bottle and fucked her in her pussy with it, is his exact words to me.”
Although we did not refer to this aspect of the testimony in our prior opinion, Mikles’s trial testimony also contained the only reference at the trial to racial matters. Mikles testified *589that while he and defendant were in a holding tank, he overheard defendant, who is Black, say to a small group of Black inmates: “ ‘So what if I did kill those two old bitches, those two old white bitches?’ ” Mikles commented with regard to this statement: “You know, it was just a little racial thing there, you know, because there is a lot of racial stuff happening in jail, you know . . . .”
On May 20, 1992, shortly before oral argument in this court, defendant requested that we take judicial notice of a number of documents contained in an exhibit submitted by another prisoner in a separate habeas corpus petition filed in the Court of Appeal. Defendant's request described the exhibit as consisting of “an extensive array of correspondence” between Mikles and the deputy sheriff who testified at the reference hearing in this case. Because the accuracy or reliability of the contents of the documents has not been demonstrated, the contents could not properly be given any evidentiary weight in this proceeding (see, e.g., People v. Rubio (1977) 71 Cal.App.3d 757, 766 [139 Cal.Rptr. 750]; Williams v. Hartford Ins. Co. (1983) 147 Cal.App.3d 893, 899 [195 Cal.Rptr. 448]), and we therefore denied the request for judicial notice. In any event, the contents of the documents, even if accurate, add nothing of substance to the evidence that was introduced at the reference hearing held in defendant’s case.
The referee found that as a result of his testimony against defendant and other inmates, Mikles obtained (1) release from a 6-year state prison sentence which previously had been imposed in a Long Beach case, (2) the imposition of a sentence of probation, with no time in custody, on a conviction for multiple robbery counts with a firearm-use allegation, a case in which sentence was pending at the time of defendant’s trial, (3) the lifting of a 42-month federal parole hold, and (4) the “clearing” of pending charges in Long Beach involving approximately 15 robberies.
There was some ambiguity in the testimony as to whether the prosecutor had agreed to write a second letter on McFarland’s behalf, bringing McFarland’s cooperation in defendant’s trial to the attention of the trial judge in McFarland’s case for consideration in connection with McFarland’s sentencing. The Attorney General strongly contests the referee’s finding that the prosecutor had agreed to write such a second letter. We need not and do not resolve the factual question whether it was one or two letters the prosecutor agreed to write on McFarland’s behalf, because we do not believe this discrepancy reasonably could have affected the jury’s assessment of McFarland’s credibility.
As noted, with respect to McFarland, the referee found that the prosecutor himself had promised that, in the event McFarland testified at Jackson’s trial, the prosecutor would write two letters on McFarland’s behalf, one to federal prison authorities in support of McFarland’s desire to have his prison term served in Arizona rather than in California, and the other in an attempt to influence McFarland’s California sentence. Although the Attorney General maintains that the record does not support the referee’s finding with regard to the second letter, the Attorney General concedes that the record does support the finding that the prosecutor agreed to write the first letter in return for McFarland’s testimony, and that under Morris, supra, 46 Cal.3d 1, this inducement should have been disclosed to the jury.
As pointed out by the lead opinion in United States v. Bagley, supra, 473 U.S. 667, 679-680 [87 L.Ed.2d 481, 492-493], footnote 9, “[t]he rule that a conviction obtained by the knowing use of perjured testimony must be set aside if there is any reasonable likelihood that the false testimony could have affected the jury’s verdict derives from Napue v. Illinois, [supra,] 360 U.S. at 271. . . . Napue antedated Chapman v. California, 386 U.S. 18 [17 L.Ed.2d 705, 87 S.Ct. 824, 24 A.L.R.3d 1065] (1967), where the 'harmless beyond a reasonable doubt’ standard was established. The court in Chapman noted that there was little, if any, difference between a rule formulated, as in Napue, in terms of ‘“whether there is a reasonable possibility that the evidence complained of might have contributed to the conviction,” ’ and a rule "’requiring the beneficiary of a constitutional error to prove beyond a reasonable doubt that the error complained of did not contribute to the verdict obtained.” ’ ” The lead opinion in Bagley then stated: “It is therefore clear, as indeed the Government concedes . . . , that this Court’s precedents indicate that the standard of review applicable to the knowing use of perjured testimony is equivalent to the Chapman harmless-error standard.” (473 U.S. at p. 680, fn. 9 [87 L.Ed.2d at pp. 492-493].)
Because we conclude that defendant has failed to establish the requisite degree of prejudice, we have no occasion to decide here what effect, if any, the United States Supreme Court's recent decision in Dawson v. Delaware (1992) 503 U.S._[117 L.Ed.2d 309, 112 S.Ct. 1093] would have on the admissibility, for impeachment purposes, of evidence of Mikles’s former membership in the Aryan Brotherhood.