PER CURIAM:

Death-row inmate Darryl Brian Barwick appeals the denial of his petition for a writ of habeas corpus pursuant to 28 U.S.C. § 2254 in the United States District Court for the Northern District of Florida. For the following reasons, the district court's order denying Barwick's petition for a writ of habeas corpus is affirmed.

I.

On the morning of March 31, 1986, Rebecca Wendt was sunbathing at her Panama City apartment-complex pool until she returned to her apartment. Around that time, another apartment-complex resident, Suzanna Capers, who also was sunbathing by the pool, observed a man walking around the complex. Capers saw the man she subsequently identified as Darryl Barwick walk towards Wendt's apartment and later from the apartment and into the woods.

That evening, Rebecca Wendt's sister, who was also her roommate, returned home to find Rebecca's body wrapped in a comforter. Investigators called to the scene found bloody footprints and fingerprints throughout the apartment. Rebecca's bathing suit had been displaced, and an autopsy revealed thirty-seven stab wounds to her upper body and several defensive wounds on her hands. The medical examiner reported that death would have occurred within three to ten minutes of the first stab wound. No evidence of sexual contact with the victim was found, but criminal laboratory tests revealed a semen stain on the comforter wrapped around the victim. Further testing indicated that the stain could have been left by two percent of the population and that Barwick fell within that two percent.

When initially questioned, Barwick denied involvement in the murder. But after he was arrested on April 15, 1986, Barwick made a full confession. Barwick told investigators that after he had observed Rebecca sunbathing, he went home, parked his car, got a knife, walked back to Rebecca's apartment complex, walked past her three times, and then followed her into her apartment. Barwick claimed that when he entered Wendt's apartment, he had only intended to steal something, but when Rebecca resisted, he lost control and stabbed her, and continued to stab her repeatedly as they struggled and fell to the floor.

Barwick was then indicted on four counts: (1) first-degree murder; (2) armed burglary; (3) attempted sexual battery; and (4) armed robbery. He was tried by a jury and convicted on all counts. By a 9-3 vote, the jury recommended that Barwick be put to death, and the judge subsequently sentenced Barwick to death.1 On appeal, however, the Florida Supreme Court reversed Barwick's convictions and sentences and remanded for a new trial.2

On the third day of his second trial, a mistrial was declared,3 and a new trial commenced on July 6, 1992. Barwick was again convicted on all counts. This time the jury unanimously recommended Barwick be put to death, and the judge so sentenced him. The trial judge found six aggravators proven beyond a reasonable doubt: (1) previous convictions of violent felonies of sexual battery with force likely to cause death or great bodily harm and burglary of a dwelling with an assault; (2) the murder was committed during an attempted sexual battery; (3) the murder was committed to avoid arrest; (4) the murder was committed for pecuniary gain; (5) the murder was especially heinous, atrocious, or cruel; and (6) the murder was committed in a cold, calculated, and premeditated manner without any pretense of moral justification.4 The trial court found no statutory mitigation, and despite recognizing that Barwick suffered abuse as a child and had some mental deficiencies, it wrote in its sentencing order that there were no non-statutory mitigating factors, either. The Florida Supreme Court affirmed Barwick's convictions and death sentence. Barwick v. State, 660 So.2d 685, 697 (Fla. 1995) (per curiam) ("Barwick II"). The United States Supreme Court denied certiorari on January 22, 1996. Barwick v. Florida, 516 U.S. 1097, 116 S.Ct. 823, 133 L.Ed.2d 766 (1996) ("Barwick III").

On March 17, 1997, Barwick filed an initial motion for post-conviction relief in the state circuit court, and he amended the motion on August 26, 2002, raising twenty-one claims in total. On December 4, 2003, the state circuit court granted an evidentiary hearing on four of the claims, reserved ruling on one, and summarily denied the remainder. In a second amended motion for postconviction relief, Barwick realleged the same twenty-one claims and added two new claims. The state circuit court issued an order denying Barwick's motion on August 28, 2007. Barwick filed an appeal with the Florida Supreme Court. While that appeal was pending, he also filed a petition for a writ of habeas corpus with the Florida Supreme Court. On June 30, 2011, the Florida Supreme Court affirmed Barwick's conviction and death sentence and also denied his motion for a writ of habeas corpus. Barwick v. State, 88 So.3d 85 (Fla.2011) (per curiam) ("Barwick IV").

On May 25, 2012, Barwick filed this federal habeas petition, raising seven issues. The district court denied all of his claims but granted a certificate of appealability ("COA") as to one issue, and a member of this Court expanded the COA to include four other claims, for a total of five claims: (1) whether Barwick's trial counsel rendered ineffective assistance related to mitigation evidence during the penalty phase; (2) whether the district court erred in denying Barwick's federal constitutional ineffective-assistance-of-trial-counsel ("IATC") claim with respect to the alleged failure of counsel to effectively challenge the guilt-phase testimony of state witness Suzanna Capers, which the jury was instructed to consider at the penalty phase; (3) whether the district court erred in denying Barwick's federal constitutional claim with respect to alleged violations of Giglio v. United States, 405 U.S. 150, 92 S.Ct. 763, 31 L.Ed.2d 104 (1972), by allegedly permitting Capers to testify falsely and by emphasizing Capers's allegedly incorrect statements to the jury; (4) whether the district court erred in denying Barwick's federal constitutional challenge to the trial court's rejection of Barwick's childhood abuse as a mitigating circumstance; and (5) whether the district court erred in denying Barwick's federal constitutional challenge to his execution as a "brain damaged, mentally impaired individual."

II.

When reviewing the denial of a habeas petition, the Court reviews de novo questions of law and mixed questions of law and fact. LeCroy v. Sec'y, Fla. Dep't Corr., 421 F.3d 1237, 1259 (11th Cir.2005). It reviews findings of fact for clear error. Id. Relief is warranted when the state court's resolution of a claim "was contrary to, or involved an unreasonable application of, clearly established Federal law, as determined by the Supreme Court of the United States," or if the ruling "was based on an unreasonable determination of the facts in light of the evidence presented in the State court proceeding." 28 U.S.C. § 2254(d)(1)-(2). We presume a state court's factual determinations to be correct, and the applicant bears the burden of rebutting this presumption by clear and convincing evidence. 28 U.S.C. § 2254(e)(1).

III.

A. Ineffective Assistance

A person challenging a conviction based on ineffectiveness of counsel must show both that his counsel provided deficient assistance and that prejudice resulted. Strickland v. Washington, 466 U.S. 668, 687, 104 S.Ct. 2052, 2064, 80 L.Ed.2d 674 (1984). Deficient assistance means "counsel's representation fell below an objective standard of reasonableness." Id. at 688, 104 S.Ct. at 2064. But a "wide range" of performance meets the standard of "reasonableness," and we apply a "strong presumption" that counsel's representation fell within that range. Id. at 689, 104 S.Ct. at 2065. Only when "counsel made errors so serious that counsel was not functioning as the `counsel' guaranteed ... by the Sixth Amendment" is counsel's assistance deemed to be constitutionally "deficient." Id. at 687, 104 S.Ct. at 2064.

Prejudice occurs when the challenger has shown "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." Id. at 694, 104 S.Ct. at 2068. So even errors that have "some conceivable effect on the outcome of the proceeding" are not enough to show prejudice. Id. at 693, 104 S.Ct. at 2067. Prejudice results only when counsel's errors were "so serious" that they deprived the defendant of a "fair trial, a trial whose result is reliable." Id. at 687, 104 S.Ct. at 2064.

When an IATC claim is based upon a failure to present mitigating evidence, we must consider "whether counsel reasonably investigated possible mitigating factors and made a reasonable effort to present mitigating evidence to the sentencing court." Henyard v. McDonough, 459 F.3d 1217, 1242 (11th Cir.2006) (per curiam). When mental health is at issue, counsel does not offer ineffective assistance when it later becomes apparent that an expert who would have testified more favorably than the expert who was actually called may have existed. See Ward v. Hall, 592 F.3d 1144, 1173 (11th Cir.2010) ("As we have held many times before, `the mere fact a defendant can find, years after the fact, a mental health expert who will testify favorably for him does not demonstrate that trial counsel was ineffective for failing to produce that expert at trial.'" (quoting Davis v. Singletary, 119 F.3d 1471, 1475 (11th Cir.1997))). When evaluating the claim, the court must "consider `the totality of the available mitigation evidence — both that adduced at trial, and the evidence adduced in the habeas proceeding' — and `reweig[h] it against the evidence in aggravation.'" Porter v. McCollum, 558 U.S. 30, 41, 130 S.Ct. 447, 453-54, 175 L.Ed.2d 398 (2009) (per curiam) (quoting Williams v. Taylor, 529 U.S. 362, 397-98, 120 S.Ct. 1495, 1515, 146 L.Ed.2d 389 (2000)).

In short, under Strickland, "[e]ven under de novo review, the standard for judging counsel's representation is a most deferential one." Harrington v. Richter, 562 U.S. 86, 105, 131 S.Ct. 770, 788, 178 L.Ed.2d 624 (2011). Moreover, the Supreme Court has emphasized that the "Strickland standard must be applied with scrupulous care, lest `intrusive post-trial inquiry' threaten the integrity of the very adversary process the right to counsel is meant to serve." Id. (quoting Strickland, 466 U.S. at 690, 104 S.Ct. at 2066).

And in a federal habeas proceeding, we must also apply deference to a state court's rejection of a Strickland claim. See id. Title 28, United States Code, Section 2254(d), amended by the Antiterrorism and Effective Death Penalty Act of 1996 ("AEDPA"), Pub.L. No. 104-132, § 104, 110 Stat. 1214 (1996), sets forth the statutory authority of federal courts to issue habeas corpus relief for persons in state custody:

In applying this standard, the Supreme Court has explained that "even a strong case for relief does not mean the state court's contrary conclusion was unreasonable." Harrington, 562 U.S. at 102, 131 S.Ct. at 786. That is, when evaluating a petitioner's IATC habeas claim,

Id. at 101, 131 S.Ct. at 785.

In short, "an unreasonable application of federal law is different from an incorrect application of federal law." Williams, 529 U.S. at 410, 120 S.Ct. at 1522. A state court's determination that a claim lacks merit is reasonable so long as "fairminded jurists could disagree" about whether the state court's determination was correct. Yarborough v. Alvarado, 541 U.S. 652, 664, 124 S.Ct. 2140, 2149, 158 L.Ed.2d 938 (2004). And "[t]he more general the rule, the more leeway courts have in reaching outcomes in case-by-case determinations." Id. Because "[t]he Strickland standard is a general one ... the range of reasonable applications is substantial." Harrington, 562 U.S. at 105, 131 S.Ct. at 788. In sum, "a habeas court must determine what arguments... supported ... the state court's decision ... [and] whether it is possible fairminded jurists could disagree [about whether] those arguments ... are inconsistent with the holding in a prior decision of [the Supreme] Court." Id. at 102, 131 S.Ct. at 786.

1. The Mitigation Claim

Barwick contends that he was denied effective representation at the penalty phase because counsel allegedly failed to adequately present mitigating evidence. Counsel presented seven mental-health experts and seven lay witnesses to detail Barwick's tragic home life, including years of sexual, physical, and mental abuse, as well as to detail Barwick's mental deficiencies, learning disabilities, and psychological problems. Nevertheless, Barwick argues that trial counsel's performance was deficient principally for two reasons: (1) counsel's "kitchen sink approach" — in which counsel presented several experts he knew would not be helpful to Barwick's case in an effort to make the defense appear more trustworthy and forthright to the jury — undermined the proper functioning of the adversarial process by presenting harmful testimony that reduced the collective reliability of the testimony; and (2) counsel relied solely on the investigation conducted by the attorney who represented Barwick in his first trial and failed to uncover additional mitigating evidence that another expert proffered during the post-conviction proceeding. The Florida Supreme Court rejected both of these arguments because Barwick failed to show either deficient performance or prejudice under Strickland. We affirm the district court's denial of Barwick's penalty-phase IATC claim based on his failure to show prejudice without deciding if trial counsel's conduct was deficient. See Strickland, 466 U.S. at 697, 104 S.Ct. at 2069 ("[T]here is no reason for a court deciding an ineffective assistance claim to ... address both components of the inquiry if the defendant makes an insufficient showing on one."). On this record, we cannot say that the Florida Supreme Court engaged in an unreasonable application of federal law.

a.

To explain the basis for our decision, we first review the evidence with respect to both of Barwick's arguments. We begin by summarizing the testimony of the three experts in particular who Barwick asserts counsel should not have presented: Drs. Annis, McClaren, and Warriner.

Dr. Lawrence Annis, a clinical psychologist, testified that he examined Barwick twice in 1986, pursuant to court order. Dr. Annis described various psychological tests that he administered to Barwick, which revealed that Barwick exhibited overall normal intelligence but showed better motor skills than verbal skills. Dr. Annis further testified that although Barwick did not seem to be bipolar or schizophrenic, he did appear to be "seeing the world differently from the way normal people would see it," and he was more sad and anxious than the typical inmate Dr. Annis examined. Additionally, Dr. Annis testified that Barwick exhibited a lot of resentment and anger, which might have resulted from physical abuse he endured as a child at the hands of his father, and that Barwick "showed many of the signs" of a "mentally disordered sex offender."5 Despite these findings, Dr. Annis testified that, in his opinion, Barwick was not insane, nor did he suffer from any mental disease or defect but that he did meet the criteria for an antisocial personality diagnosis, although Dr. Annis did not officially diagnose Barwick with this condition.

Dr. Harry McClaren, a psychologist specializing in forensic psychology, also testified that he examined Barwick pursuant to a court order in 1986. Dr. McClaren administered several psychological tests on Barwick, one of which revealed that Barwick's overall intelligence was in the normal range but that his verbal intelligence was below average. Dr. McClaren testified that Barwick exhibited "a degree of brain dysfunction" and that Barwick "had difficulties in the sexual area ... [which] were related to what happened in this homicide." Furthermore, as part of his examination and assessment, Dr. McClaren testified that he spoke with several members of Barwick's family, including his mother, a sister, and a brother, as well as Barwick's girlfriend, and other people who had interacted with Barwick; in short, Dr. McClaren testified that he did "everything [he] could to understand [Barwick.]" These discussions and his review of other written materials revealed that Barwick's father had abused Barwick as a child, and Dr. McClaren told the jury that this abuse "certainly" could have contributed to Barwick's sexual difficulties. Dr. McClaren stated that he did not believe that Barwick was insane because that conclusion could be drawn only if any mental disease or defect that Barwick had been suffering from was so severe that it rendered him incapable of appreciating right from wrong or conforming his conduct to the law, which Dr. McClaren did not believe to be the case. Nor did Dr. McClaren believe that Barwick was operating under the influence of extreme mental or emotional disturbance at the time of the offense. Finally, Dr. McClaren testified that Barwick exhibited the criteria of a mentally disordered sex offender and that he had diagnosed Barwick with an antisocial personality disorder.

Dr. Clell Warriner, a clinical psychologist, testified that he first evaluated Barwick in 1980, when Barwick was just thirteen years old, at the request of an attorney defending Barwick on juvenile charges. By that time, Dr. Warriner told the jury, Barwick had already exposed himself to a girl, had hit another girl after she had called him a name, and had touched a third woman inappropriately. These prior instances of sexual misconduct may have been inadmissible if offered by the government.6 Dr. Warriner further testified that he examined Barwick for a second time three years later, in 1983, this time at the request of an attorney representing Barwick on sexual-battery charges. Although when Dr. Warriner first evaluated Barwick he thought that Barwick could be rehabilitated, Dr. Warriner testified that after having evaluated Barwick a second time, he concluded that Barwick was a psychopathic sexual deviant who was extraordinarily dangerous and incapable of being rehabilitated. Dr. Warriner reached this same conclusion when he examined Barwick for a third time, this time in connection with the crime at issue in this habeas petition. Finally, Dr. Warriner speculated that there were likely other episodes of escalating sexual violence for which Barwick was not caught.

Relevant to Barwick's second argument — that counsel merely relied on the investigation conducted by Barwick's counsel during his first trial7 and should have been able to find an expert to testify more favorably than the experts that he did present — is the testimony of Dr. Hyman Eisenstein, proffered at his post-conviction hearing. Because it is important to understanding our determination today, we summarize Dr. Eisenstein's testimony in some detail.

Dr. Eisenstein first stated that he had testified in dozens of criminal cases in both state and federal court in Florida but noted that he had always testified for the defense.8 He explained that he evaluated Barwick in 2000 and again in 2002 — fourteen and sixteen years after the commission of the crime, during which time Barwick had been incarcerated — and administered numerous psychological tests to Barwick. Based on his examination, Dr. Eisenstein found that Barwick exhibited slightly below-normal intelligence and stronger non-verbal than verbal intelligence. He opined that the difference in these intelligence measures probably informed Dr. McClaren's conclusion that Barwick exhibited some brain dysfunction. In addition, Dr. Eisenstein expressed his belief that Barwick suffered from physical brain damage, particularly in the left temporal region. Overall, Dr. Eisenstein testified that the results of these tests were consistent with the findings of the experts who had previously testified, including Drs. Annis and McClaren.

Besides testing, Dr. Eisenstein spoke with members of Barwick's family, including two brothers, two sisters, and his mother. Dr. Eisenstein described the physical abuse that Barwick and his siblings suffered at the hands of their father, the sexually charged and abnormal nature of the Barwick household, and the emotional abuse that the Barwick children endured as a result of name-calling by Barwick's father. Because of Barwick's mental deficiencies, Dr. Eisenstein opined that Barwick was subjected to additional emotional abuse and was more vulnerable to the abuse that he received than his brothers.

Based on Dr. Eisenstein's examination and review of available information, he diagnosed Barwick with intermittent explosive disorder. According to Dr. Eisenstein, this diagnosis made applicable to Barwick the statutory mitigator that the defendant could not substantially conform his conduct to the requirements of the law. Dr. Eisenstein also testified that he believed Barwick qualified for the extreme-emotional-distress statutory mitigator because "somebody with normal emotional and mental functioning would not commit such acts," and "only ... the extreme form of the emotional or mental impairment ... could explain ... what happened." Also, although Barwick was actually nineteen years old at the time that he committed the crime in this case, Dr. Eisenstein testified that he believed that Barwick was actually "functioning at an early-adolescence stage," somewhere between the ages of 11 and 14, at the time.

On cross-examination, Dr. Eisenstein admitted that he had not asked Barwick several questions regarding what Barwick remembered about the events leading up to the murder, despite earlier testimony that he had tried to collect as much information as possible to understand why Barwick committed the murder. Dr. Eisenstein also conceded that he had not reviewed Barwick's trial testimony and the confession that Barwick had given police regarding why he committed the attack. Moreover, although the trial transcript revealed that Barwick had told his brothers that he killed Rebecca because she had seen his face and he did not want to go back to prison, Dr. Eisenstein did not ask Barwick's brothers about this conversation. During cross-examination, Dr. Eisenstein also acknowledged that he had not reviewed a report prepared by a neurologist who had administered an electroencephalogram (EEG) on Barwick in 1986, which showed that although there was "some slowing" in Barwick's brain, it was a "normal neurologic evaluation." Finally, although Dr. Eisenstein believed that Barwick exhibited four of the seven criteria that inform whether an individual suffers from an antisocial personality disorder, and the presence of only three criteria is necessary to make such a diagnosis, Dr. Eisenstein declined to diagnose Barwick with the disorder.

b.

Turning to the arguments that Barwick advances in this habeas petition, we make a few observations. First, we note that both Drs. Annis and McClaren had testified for the government at both the guilt and penalty phases in Barwick's first trial, and the record indicates that the state would have called at least Dr. McClaren if Barwick's counsel had not. Accordingly, the testimony that Barwick was not insane because he did not suffer from a mental disease or defect sufficient to make this diagnosis, that he knew right from wrong, and that he was not under the influence of extreme mental or emotional disturbance, to which Barwick takes most offense, most likely still would have been presented, and therefore would not have been avoided even if Barwick's counsel had not called these witnesses.9

We also note that Drs. Annis, McClaren and Warriner testified similarly in many respects to the other experts that counsel called, as well as to Dr. Eisenstein, Barwick's preferred expert. For instance, Drs. Annis's and McClaren's findings regarding Barwick's intelligence were consistent with those of Dr. Eisenstein. Similarly, Drs. Annis, McClaren and Eisenstein, as well as several other experts, discussed the abuse that Barwick suffered, which was extensively detailed by the lay witnesses whom Barwick's counsel presented, and each of these experts testified that the abuse could have contributed to Barwick's actions. Barwick took special offense to Dr. Warriner's testimony that Barwick was a psychopathic sexual deviant and that he could not be rehabilitated, but similar testimony was also proffered by two other experts: Dr. Walker and James Beller, a clinical psychologist — neither of whose testimony he challenges.

Furthermore, although Barwick contends that this portion of Dr. Warriner's testimony was harmful and led the jury to conclude that the death penalty was the most appropriate sentence, the same testimony arguably could have supported a finding that Barwick was unable to conform his conduct to the law, that he suffered from a mental disease or defect, or that he was under the influence of extreme mental or emotional disturbance.10 Likewise, despite Barwick's characterization of Dr. Eisenstein's testimony, Dr. Eisenstein's explicit finding that Barwick could not conform his actions to the law could have also have led the jury to believe that Barwick would not have been able to conform his actions to the law if he were sentenced to prison and eventually released and that a death-penalty sentence was appropriate. It is difficult to predict the manner in which a judge and jury will construe mental-health issues and their impact on a defendant's behavior; sometimes such evidence will be viewed as mitigating, and other times it may be construed as damaging. Cf., Suggs v. McNeil, 609 F.3d 1218, 1231 (11th Cir.2010) (pointing out that the use of many different types of evidence at the penalty phase of a capital case is a double-edged sword). Although it is clear from the unanimous jury recommendation that Barwick's counsel's mitigation strategy failed, we remain mindful of the Supreme Court's warning that hindsight should not affect our interpretation of counsel's performance. Strickland, 466 U.S. at 689, 104 S.Ct. at 2065.

Finally, a review of the mitigation testimony offered by the experts called by defense counsel reveals that it was not as inconsistent as Barwick suggests. All of the testimony elicited tells the same basic story: Barwick suffered substantial abuse as a child, this abuse affected his mental state, and Barwick's impaired and abnormal mental state contributed to the crime that he eventually committed. Usually, habeas relief will not be provided under these circumstances. See Holsey v. Warden, Ga. Diagnostic Prison, 694 F.3d 1230, 1266 (11th Cir.2012).

But even if we were to find a Strickland violation based upon the record before us, at this point in the proceedings, that is not enough for Barwick to prevail. Now our role is limited to considering whether the Florida Supreme Court's conclusion that there was not a Strickland violation was reasonable. See Harrington, 562 U.S. at 101, 131 S.Ct. at 785. Stated another way, our job is to determine whether "fairminded jurists could disagree" as to whether the Florida Supreme Court's conclusion was correct, and we are prohibited from upsetting the Florida Supreme Court's ruling so long as that ruling is debatable. See Yarborough, 541 U.S. at 664, 124 S.Ct. at 2149. In this case, it is, so, as the district court concluded, Barwick's habeas petition must be denied.

In its decision denying Barwick's ineffective-assistance-of-trial-counsel claim, the Florida Supreme Court first summarized the testimony proffered by all seven mental-health experts and all seven lay witnesses called by Barwick's counsel at the penalty phase. See Barwick IV, 88 So.3d at 96-99. The Florida Supreme Court also evaluated and compared that evidence to the testimony of Dr. Eisenstein. Id. at 100. It highlighted two main differences between Dr. Eisenstein's testimony and that of the experts presented at trial: (1) Dr. Eisenstein, unlike the trial experts, found the presence of two statutory mitigators (i.e., that Barwick acted under influence of extreme mental or emotional disturbance, and that his capacity to conform his conduct to the requirements of the law was substantially impaired); and (2) Dr. Eisenstein disagreed with the defense experts who in fact diagnosed Barwick with an antisocial personality disorder. Barwick IV, 88 So.3d at 100.11

In rejecting Barwick's penalty-phase IATC claim, the Florida Supreme Court stated that it "has consistently rejected the proposition that trial counsel's performance is deficient simply because a defendant finds an expert, in postconviction proceedings, that will testify more favorably for him." Id. It also explained that Barwick was not prejudiced by counsel's conduct. Id. ("The fact that some testimony proved to be unfavorable to Barwick does not undermine our confidence in the verdict."); see id. at 94 (when setting forth the standard to establish a Strickland violation, stating that "[a] court considering a claim of ineffectiveness of counsel need not make a specific ruling on the performance component of the test when it is clear that the prejudice component is not satisfied").

Evaluating this ruling under AEDPA's deferential standard, we must affirm the denial of Barwick's petition for habeas corpus relief. For one thing, Barwick's arguments here concern mitigation, not aggravation; accordingly, the five aggravating factors found to support the death-penalty sentence would remain, even if counsel had not presented the testimony of Drs. Annis, McClaren and Warriner. And even though Dr. Eisenstein testified to the presence of two statutory mitigating circumstances and another nonstatutory mitigating circumstance, the Supreme Court has explained that "[t]he sentencer ... may determine the weight to be given relevant mitigating evidence." Eddings v. Oklahoma, 455 U.S. 104, 114-15, 102 S.Ct. 869, 877, 71 L.Ed.2d 1 (1982). In weighing the aggravating evidence against the mitigating testimony of Dr. Eisenstein, the Florida Supreme Court identified perceived shortcomings related to Dr. Eisenstein's testimony, including Dr. Eisenstein's failure to review (1) Barwick's confession to the police, (2) Barwick's confession to his brothers and his father, and (3) the police and sentencing reports pertaining to Barwick's prior rape case. Based on these alleged deficiencies, the Florida Supreme Court reasoned that the government might have been able to create doubt as to the reliability of Dr. Eisenstein's professional opinion, had he testified. See Barwick IV, 88 So.3d at 100. In addition, the record shows that Dr. Eisenstein has previously testified for the defense only. For these reasons, we cannot conclude there is a reasonable probability that the jury would have afforded Dr. Eisenstein's testimony much, if any, weight — at least not sufficient to undermine our confidence in the outcome.

Based upon the events and facts of this case, the fact that the aggravating circumstances would have still greatly out-weighed any mitigating circumstances, and a unanimous jury recommendation, we cannot say that the Florida Supreme Court was unreasonable when it determined that its confidence in the sentence imposed was not undermined by any alleged deficient performance by Barwick's counsel.

2. Failure-to-Impeach Claim

Next, Barwick contends that counsel rendered ineffective assistance at the guilt phase of his trial when he failed to impeach state witness Suzanna Capers. At trial, Capers had testified that when she observed Barwick, she felt suspicious, worried and uneasy:

Shortly after the murder, though, Capers had provided the following deposition testimony:

Based on these excerpts, Barwick argues that Capers's testimony at his third trial was inconsistent with her previous testimony and that his trial counsel should have attempted to impeach her testimony. Moreover, he complains that the prosecution relied on Capers's more damaging statements during its closing argument in the guilt phase of his third trial. The prosecutor stated,

Because the jury was instructed to consider evidence it heard during both the guilt and penalty phases when deciding on its advisory sentence, Barwick contends that the jury erroneously viewed as aggravating evidence a portrayal of him as a "stalking, lurking predator who evaluated possible victims before deliberately selecting one."12

As with his previous IATC claim, to succeed, Barwick needs to show not only that his counsel rendered ineffective assistance under Strickland, but also that the Florida Supreme Court's conclusion that counsel was not ineffective was contrary to or an unreasonable application of clearly established Federal law as determined by the Supreme Court, or that its decision resulted from an unreasonable determination of the facts in light of the evidence presented at trial. See 28 U.S.C. § 2254(d). Barwick cannot carry this heavy burden.

The Florida Supreme Court denied Barwick's IATC claim for failure to impeach Capers because it found that Barwick could not show prejudice. See Barwick IV, 88 So.3d at 96. Specifically, the court said, "Barwick's claim as it relates to the penalty phase of trial also is without merit; the jury returned a unanimous verdict recommending a death sentence, and there exist five valid aggravating circumstances, with minimal mitigating evidence, supporting the sentence." Id.

Thus, the lack of prejudice related to any alleged deficient performance due to the failure of counsel to cross-examine Capers formed the basis for the Florida Supreme Court's ruling, and we are required to pay deference to this determination under 28 U.S.C. § 2254(d). Capers's testimony was at most tangentially related to one aggravating circumstance. To the extent Capers's testimony constituted non-statutory aggravation, there is no reasonable probability that its omission would have changed the outcome of the penalty phase given the unanimous jury verdict for death, five valid and weighty aggravating circumstances, and minimal mitigating evidence supporting the sentence. It would have barely changed Barwick's sentencing profile. Under these circumstances, we cannot say that the Florida Supreme Court unreasonably applied Strickland's prejudice prong when it determined that counsel's failure to cross-examine Capers did not prejudice Barwick.

B. Giglio Claim based on Suzanna Capers's Testimony

The Supreme Court has made clear that "deliberate deception of a court and jurors by the presentation of known false evidence is incompatible with rudimentary demands of justice." Giglio, 405 U.S. at 153, 92 S.Ct. at 766 (citation and quotation marks omitted). Thus, when the prosecution engages in these acts, it may form a basis for either overturning a conviction or sentence. The Florida Supreme Court accurately set forth the rules of law and standards of review that govern the consideration of a Giglio claim as follows:

Barwick IV, 88 So.3d at 103.

Barwick argues that the prosecutor violated Giglio because he knew that the testimony he elicited from Capers and emphasized at closing at Barwick's third trial was allegedly false in that it differed from the testimony she gave at Barwick's first trial and in a deposition she gave nearer in time to the murder. Barwick contends the testimony was material "because the jury did not hear the witness say she had seen an innocent man walking around the complex, mumbling to himself, but instead that she saw a suspicious man who was trying to indicate something to Capers or frighten her in some way." Id. at 105.

The Florida Supreme Court found that Barwick failed to prove that Capers's testimony was false. It stated, "Barwick does not demonstrate that the witness's testimony as to the facts she observed has changed, only that Ms. Capers's interpretation of those facts differed between her 1986 and 1992 testimony." Id. Under the deferential § 2254(d) standard, we cannot say that the Florida Supreme Court's finding that the statements were not false, nor could they be, because they did not concern objective facts that were either true or not true, but rather subjective opinions that may have evolved,13 is "contrary to" or "an unreasonable application of Federal law," or an "unreasonable determination of the facts in light of the evidence presented." See 28 U.S.C. § 2254(d)(1)-(2).

C. Claim Regarding the Rejection of Childhood Abuse as a Mitigating Factor

Barwick also claims that the sentencing judge improperly failed to consider nonstatutory mitigating evidence presented at the penalty phase related to the child abuse that he suffered. A capital sentencer must consider and give effect to mitigation evidence that is presented. See Eddings, 455 U.S. at 114-15, 102 S.Ct. at 876-77. As the Supreme Court has stated,

Id. at 114-15, 102 S.Ct. at 876-77 (emphasis added; original emphasis omitted).

To support his claim, Barwick relies on a portion of the sentencing order that states, "The court does not find in this case that the abuse received by the defendant as a child is a mitigating circumstance." The Florida Supreme Court found on direct appeal, however, when the sentencing order is read in context, it is clear that the judge did in fact consider the abuse that Barwick endured as a child, satisfying Eddings's requirement. See Barwick II, 660 So.2d at 696. The sentencing order states,

(emphasis added).

When analyzing Barwick's failure to consider mitigation claim, the Florida Supreme Court wrote that "the judge here recognized that the evidence established that Barwick was abused as a child," which the court recognized as "mitigating in nature" and "an appropriate circumstance for the court to consider." Barwick II, 660 So.2d at 696. It also acknowledged that "the trial judge stated that he did not consider Barwick's history of child abuse as a mitigating factor," but nevertheless found that "the judge properly considered evidence of abuse in imposing the death sentence." Id. The Florida Supreme Court emphasized that the sentencing order stated the trial court had "considered and weighed each of the ... statutory and non-statutory mitigating circumstances that are established by the evidence or on which there ha[d] been any significant evidence produced." Id. "This statement indicates that the trial judge weighed the [child abuse] factor as ultimately required... [and therefore] sufficiently considered the mitigating evidence presented on this factor." Id. As Barwick points out, "extensive evidence was presented at Barwick's penalty phase regarding the abuse he endured at the hands of his father."

In light of these circumstances, the relevant question is whether it was objectively unreasonable to conclude, as the Florida Supreme Court did, that the trial judge considered Barwick's child abuse as a mitigating circumstance when it determined his sentence. Id. Keeping in mind that "[a] state court's application of clearly established federal law or its determination of the facts is unreasonable only if no `fairminded jurist' could agree with the state court's determination or conclusion," Holsey, 694 F.3d at 1257 (quoting Harrington, 562 U.S. at 101, 131 S.Ct. at 786), we cannot say the Florida Supreme Court's conclusion that the trial judge considered the abuse is objectively unreasonable when the order is read in its entirety, as the Florida Supreme Court did.

To be sure, the isolated statement on which Barwick relies is troubling to the extent it suggests that the trial court may not have given any consideration to the child abuse as mitigating because Barwick's siblings were also abused and "grew up to be responsible persons," or because Barwick's child abuse did not "result in or contribute to [his] criminal behavior." Barwick II, 660 So.2d at 695-96. Failure to give any consideration to Barwick's child abuse for either of these reasons would be contrary to clearly established federal law. See, e.g., Smith v. Texas, 543 U.S. 37, 45, 125 S.Ct. 400, 405, 160 L.Ed.2d 303 (2004) (rejecting the notion that there must be a specific nexus between defendant's troubled childhood or limited mental capabilities and capital murder before allowing a jury to consider such evidence for mitigation purposes); Eddings, 455 U.S. at 114-15, 102 S.Ct. at 877 (holding a capital sentencer may not give relevant mitigation evidence "no weight by excluding such evidence from ... consideration"). And the sentencing order could have been more carefully written to remove any ambiguity about the trial court's weighing process. For example, the trial court could have said something along the lines of the following: The Court does not find in this case that the abuse received by the defendant as a child is a mitigating circumstance sufficient to outweigh the substantial and numerous aggravating factors. But it is not appropriate for us to rewrite a state trial court's order or a state appellate court's reasoned opinion when evaluating them under § 2254(d).

The most that can be said for the sentencing court's order is that it is open to interpretation. That being so, even under pre-AEDPA habeas jurisprudence, we must give deference to the Florida Supreme Court's resolution of an ambiguity in the state trial court's order unless its resolution is not fairly supported by the record. See Wainwright v. Goode, 464 U.S. 78, 83-85, 104 S.Ct. 378, 381-82, 78 L.Ed.2d 187 (1983). Here, the Florida Supreme Court's factual determination that the trial judge did consider and weigh Barwick's child abuse mitigating evidence is fairly supported by the record and thus entitled to deference.

Additionally, under AEDPA, we are also obligated to give the Florida Supreme Court's interpretation of the sentencing order the benefit of the doubt. See Renico v. Lett, 559 U.S. 766, 773, 130 S.Ct. 1855, 1862, 176 L.Ed.2d 678 (2010) ("AEDPA... imposes a highly deferential standard for evaluating state-court rulings, and demands that state-court decisions be given the benefit of the doubt." (citations omitted) (quotation marks omitted)); see also Wood v. Allen, 558 U.S. 290, 301, 130 S.Ct. 841, 849, 175 L.Ed.2d 738 (2010) ("[A] state-court factual determination is not unreasonable merely because the federal habeas court would have reached a different conclusion in the first instance."). Because the Florida Supreme Court's conclusion that the trial judge did, in fact, consider Barwick's child abuse as a mitigating circumstance did not involve an unreasonable application of clearly established federal law or an unreasonable determination of the facts, see 28 U.S.C. § 2254(d), Barwick's petition on this claim must be denied.

Finally in this regard, we are also mindful that the Florida Supreme Court concluded that "[a]ny error in articulating the particular mitigating circumstance was harmless." Barwick II, 660 So.2d at 696 (citing Armstrong v. State, 642 So.2d 730 (Fla.1994) (per curiam)). We understand the court's citation to Armstrong to mean that any error in "the trial judge's articulation of how he considered the mitigating circumstances and aggravating circumstances... was harmless beyond a reasonable doubt" because the five valid and weighty aggravating circumstances in this case strongly outweigh the nonstatutory mitigation submitted by Barwick during his penalty phase. See Armstrong, 642 So.2d at 739. There is nothing objectively unreasonable about the Florida Supreme Court's alternative harmless error analysis based on the record in this case.

D. Claim that Executing Barwick is Unconstitutional Because He is Mentally a Minor

Finally, Barwick argues that, while he was nineteen-and-one-half years old at the time that he killed Rebecca Wendt, he presented expert psychological evidence at his post-conviction proceeding that his mental functioning was equivalent to that of an ordinary 11-to-13-year-old person, and his intellectual functioning equivalent to that of an ordinary 12-to-14-year-old person. Thus, he asserts that "[w]hen one considers mental capacity and level of functioning, there is no sustainable rationale for imposing the death penalty [here]... and not upon the class of individuals outlined in [Roper v.] Simmons [, 543 U.S. 551, 568, 125 S.Ct. 1183, 1194, 161 L.Ed.2d 1 (2005)]. See, e.g., City of Cleburne, Texas, et al. v. Cleburne Living Center, Inc., et al., 473 U.S. 432, 439, 105 S.Ct. 3249, 87 L.Ed.2d 313 (1985) ("The Equal Protection Clause of the Fourteenth Amendment commands that no State shall `deny to any person within its jurisdiction the equal protection of the laws,' which is essentially a direction that all persons similarly situated should be treated alike.")."

The Eighth Amendment provides, "Excessive bail shall not be required, nor excessive fines imposed, nor cruel and unusual punishments inflicted." The provision is applicable to the States through the Fourteenth Amendment. Furman v. Georgia, 408 U.S. 238, 239, 92 S.Ct. 2726, 2727, 33 L.Ed.2d 346 (1972) (per curiam). The Supreme Court has looked to "evolving standards of decency" to guide its determination of when the imposition of a particular punishment would be "cruel and unusual." See Trop v. Dulles, 356 U.S. 86, 100-01, 78 S.Ct. 590, 597-98, 2 L.Ed.2d 630 (1958) (plurality opinion).

In Roper v. Simmons, the Supreme Court held that the imposition of the death penalty on those less than eighteen years old would be "cruel and unusual," in violation of the Constitution. 543 U.S. 551, 568, 125 S.Ct. 1183, 1194, 161 L.Ed.2d 1 (2005). The Court rested its holding in part on the fact that several differences exist between juveniles and adults. These differences include a lack of maturity, an underdeveloped sense of responsibility, a greater susceptibility to negative influences and outside pressures, and the fact that juveniles' personality traits are more transitory and less fixed. Id. at 569-70, 125 S.Ct. at 1195-96.

But even if we were to agree with Barwick that sentencing to death one who has reached the chronological age of legal maturity but who possesses the mental and intellectual capabilities of a juvenile would be unconstitutional,14 we can grant relief only if the state court's denial of his claim was contrary to or an unreasonable application of clearly established Federal law. Although the Florida Supreme Court denied this claim as procedurally barred, it nevertheless evaluated Barwick's claim on the merits, stating,

Barwick IV, 88 So.3d at 106.

Setting aside Barwick's procedural default, the district court also addressed the Florida Supreme Court's resolution of the merits of his claim:

We agree with the district court's analysis. We note with regard to whether a state court's application of federal law is unreasonable that this Court has clarified that state courts are not obligated to extend legal principles set forth by the Supreme Court because AEDPA requires only that state courts "fully, faithfully and reasonably follow legal rules already clearly established by the Supreme Court." Hawkins v. Alabama, 318 F.3d 1302, 1307 n. 3 (11th Cir.2003). Accordingly, we cannot say that the Florida Supreme Court's opinion was an unreasonable application of federal law when it considered this claim.

IV.

For the foregoing reasons, the district court's order denying Barwick's petition for habeas corpus is AFFIRMED.