Full opinion text
TJOFLAT, Circuit Judge: In April 1992, Travis Hittson and Edward Vollmer, who were enlisted men in the Navy, brutally killed, mutilated, and dismembered their shipmate Conway Ut-terbeck. Hittson confessed to the crime, and in February 1993 he was convicted of murder in the Superior Court of Houston County, Georgia. During the penalty phase of his trial, Hittson tried to show that his co-defendant, Vollmer, had planned the murder and manipulated Hitt-son into helping him carry it out. This strategy fell short and the jury returned a unanimous death sentence, finding as an aggravating factor that the murder “was outrageously or wantonly vile, horrible, or inhuman.” See O.C.G.A. § IT — 10—30(b)(7). After Hittson exhausted his direct appeal and collateral attack remedies in the Georgia courts, he petitioned the United States District Court for the Middle District of Georgia for a writ of habeas corpus pursuant 28 U.S.C. § 2254. In his petition, Hittson presented twenty separate claims for relief. Those relevant to this appeal concern the penalty phase of his trial: (1) The trial court erroneously allowed the State’s psychologist to testify to statements made by Hittson during a court-ordered mental-health examination, in violation of Hittson’s Fifth Amendment right against self-incrimination and Sixth Amendment right to the effective assistance of counsel. (2) Hittson’s attorneys failed to properly present to the jury expert testimony regarding his background and mental condition, thus denying him his Sixth Amendment right to the effective assistance of counsel. And (3) the State withheld exculpatory evidence in violation of the Due Process Clause of the Fourteenth Amendment and the rule of Brady v. Maryland — to wit, a Navy psychiatric report diagnosing Vollmer with severe Antisocial Personality Disorder, and two letters written by Vollmer from jail following his arrest, in which he discussed the murder. The District Court found that Hittson was entitled -to habeas relief from his death sentence based on the State psychologist’s testimony. Hittson v. Humphrey, No. 5:01-cv-384 (MTT), 2012 WL 5497808, at *56 (M.D.Ga. Nov. 13, 2012). The court found that trial court’s allowance of the psychologist’s testimony denied Hittson his Fifth and Sixth Amendment rights under Estelle v. Smith, 451 U.S. 454, 101 S.Ct. 1866, 68 L.Ed.2d 359 (1981), and that the testimony had a “substantial and injurious effect” on the jury’s death sentence and was therefore not harmless, see Brecht v. Abrahamson, 507 U.S. 619, 638, 113 S.Ct. 1710, 1722, 123 L.Ed.2d 353 (1993). The court denied the remainder of Hittson’s claims for relief. On appeal, the State now concedes that the trial court’s admission of the psychologist’s testimony violated Hittson’s constitutional rights and does not appeal the District Court’s ruling on this point — leaving only the question of whether the admission of the testimony was harmless error under Brecht. Hittson also cross-appealed the District Court’s denial of some of his penalty phase challenges. The District Court granted Hittson a certificate of appealability (“COA”) on his Brady claims, and we expanded the COA to include his ineffective-assistance-of-counsel claim — that counsel failed to present expert testimony relating to Hittson’s background and mental condition. We expanded the COA a second time after the Supreme Court decided Trevino v. Thaler, — U.S. -, 133 S.Ct. 1911, 185 L.Ed.2d 1044 (2013) — by which point briefing was already underway in this appeal. Trevino recognized certain circumstances in which a federal court may excuse a habeas petitioner’s failure to properly raise his claims in state court. — U.S. at-, 133 S.Ct. at 1920-21; see also Martinez v. Ryan, — U.S. -, 132 S.Ct. 1309, 1320-21, 182 L.Ed.2d 272 (2012). Before Trevino came down, Hittson sought leave from the District Court to add four new claims to his federal petition — claims that he had not raised in any of his state proceedings. The District Court denied the motion. Because Trevino has some bearing on the District Court’s analysis, we expanded Hittson’s COA to decide: Whether Hittson should be allowed to amend his federal habeas petition to include claims of ineffective assistance of trial counsel which were previously defaulted through prior counsel in state habeas proceedings in light of the United States Supreme Court’s ruling in Trevino v. Thaler.... After reviewing the record and entertaining the parties’ arguments in open court, we (1) reverse the District Court’s grant of habeas relief setting aside Hitt-son’s death sentence based on the State psychologist’s testimony, (2) affirm the District Court’s denial of Hittson’s Brady claims and ineffective-assistance-of-counsel claim, and (3) hold that Trevino does not enable Hittson to raise new claims that he failed to litigate in state court. Part I of this opinion describes the crime, as presented to the jury in the State’s case in chief, and the law enforcement’s investigation. Part II covers Hitt-son’s 1993 trial, his direct appeal to the Georgia Supreme Court, and that court’s refusal to grant him habeas corpus relief. Part III covers the § 2254 proceedings in the United States District Court and its granting of the writ setting aside Hittson’s death sentence. Part IV explains the standard we apply under § 2254 in reviewing the Georgia courts’ denial of Hittson’s constitutional claims. In parts V, VI, and VII, we review and dispose of those claims. Part VIII explains our reasons for concluding Hittson may not rely on Trevino to excuse his procedural default. And we briefly conclude in part IX. I. A. In the spring of 1992, Travis Hittson, Edward Vollmer, and Conway Utterbeck were stationed aboard the USS Forrestal, an aircraft carrier that was based in Pensacola, Florida, at the time. They were all assigned to the electrical division of the engineering department. Vollmer and Hittson were on the same work detail, and Vollmer was Hittson’s Leading Petty Officer. Utterbeck had a different assignment but worked in a similar capacity in the same area of the ship. On Friday, April 3,1992, Vollmer invited Hittson and Utterbeck to come with him to his parents’ house in Warner Robins, Georgia, for the weekend. His parents were out of town. Apparently neither Hittson nor Utterbeck was aware that the other had also been invited until shortly before they left Pensacola. The three men arrived at Vollmer’s parents’ house late Friday evening, but they did not have a key, so they spent the night in a storage shed behind the house. On Saturday, April 4, a friend of Vollmer’s parents came by to check on the house; finding Vollmer and the two others there, he gave them a key. The three sailors spent most of the day on Saturday hanging around the house, but sometime Saturday evening, Hittson and Vollmer went out drinking. They left Utterbeck at the house. Early in the morning of Sunday, April 5, after several hours of drinking, Hittson and Vollmer headed back to the Vollmer residence. According to the statement later given by Hittson to law enforcement, he was very drunk by that time. On the drive back, Vollmer worked Hittson up by telling him that Utterbeck was “going to get us” — that Utterbeck was plotting to kill the two of them — so “we’ve got to get him” by killing him first. At some point— though it is not clear when — Vollmer told Hittson that Utterbeck had a hit list with Hittson’s and Vollmer’s names on it. When they pulled into the driveway, Vollmer put on a bulletproof vest and a long trench coat and grabbed a sawed-off shotgun and a .22 caliber handgun from his car. He gave Hittson an aluminum bat that was also in the car and told Hittson that Utterbeck was waiting for them inside the house and was planning to shoot them. Vollmer instructed Hittson to go in first and “get him” and then “get him in the kitchen” — so they would not make a mess on the carpet. When Hittson entered the house, he found Utterbeck asleep in a recliner in the living room. Hittson sneaked up on him and hit him in the head with the bat. Utterbeck woke up and jumped up out of the chair. Hittson hit him in the head again, knocking him to the floor. Utterbeck raised a hand to defend himself, so Hittson hit his hand with the bat and then hit him in the head a third time. The third hit was apparently enough to subdue Utter-beck. Hittson dragged him by his hands into the kitchen, where Vollmer was waiting. Utterbeck was still conscious and asked Hittson, “what did I ever do to you?” Vollmer gave Hittson the .22 pistol and stood on Utterbeck’s hand to keep him from struggling. Utterbeck screamed “no, no,” and begged for his life, but Hittson shot him point blank in the forehead. In his own words, “I had no emotion or nothing on my face. I know I didn’t. I was cold and Vollmer steps on his hand and ... handed me the gun, I shot him.” Hittson and Vollmer stripped Utter-beck’s body, taking the $62 they found in his pockets. They left the body in the kitchen and went to a nearby Waffle House to get something to eat. Upon their return, Vollmer told Hittson that they had to dismember the body and clean up the house to conceal the crime. They initially tried to' cut up the body with a serrated steak knife from the kitchen, but then switched to a hacksaw from the tool shed out back. They also found a piece of slate in the shed, which they placed under the body to avoid scratching up the kitchen floor. Following Vollmér’s directions, Hittson sawed off one of Utterbeck’s hands and began working on sawing off his head, but got sick and had to stop. Vollmer finished sawing off the head, the other hand, and both feet. Vollmer also skinned part of Utterbeck’s arm and chest with a knife and a pair of pliers. The autopsy later showed that Utterbeck’s buttocks and penis were partially skinned and his testicles and rectum were removed. Hitt-son denied performing the sexual mutilation and stated that he had not seen Vollmer do it either. After finishing their grisly task, Hittson and Vollmer wrapped Utterbeck’s torso and severed body parts in plastic bags and left them in the kitchen while they drove to a nearby wooded area to dig a shallow grave. As they were returning to Vollmer’s parents’ house — around 10:30 on Sunday morning — they happened to pull onto the highway in front of a local woman who was traveling in the same direction. The woman took notice of Vollmer’s car, which had an out-of-state license plate and was pulling off of a lightly traveled dirt road that led to an undeveloped tract of land owned by a friend. Suspicious, she wrote down the license plate number and a description of the car, which she later turned over to the Houston County Sheriffs Office after Utterbeck’s torso was discovered on the property two months later. Hittson and Vollmer returned to Vollmer’s parents’ house and began cleaning the blood off the kitchen floor and the living room carpet. Vollmer’s sister-in-law (who lived nearby) came by around noon on Sunday, while they were still cleaning. Vollmer left with her to go grab a bite to eat, without ever letting her inside the house. While they were gone, Hittson kept cleaning. When Vollmer returned, he and Hittson drove back out to the grave to bury Utterbeck’s torso and then went back to the house to finish cleaning. The family friend who had given them the key came by Sunday evening to check on the house again. Hittson had to quickly hide Utter-beck’s clothes and throw a blanket over a lingering blood spot in the living room. When the family friend asked where the third guy was, Vollmer told him that Ut-terbeck was asleep in the back room. Hittson and Vollmer finally finished cleaning up the house sometime Sunday evening, and so they packed up and set out for Pensacola. They put Utterbeck’s severed hands, head, and feet in the trunk of Vollmer’s car, along with a few other pieces of evidence, including Utterbeck’s clothing, his identification card, and the .22 shell casing. They threw Utterbeck’s clothing and ID card in a dumpster close to Vollmer’s parents’ house. Before leaving Warner Robins, they stopped at Vollmer’s sister-in-law’s for about an hour to say goodbye. As they drove back to Pensacola, Vollmer tried to find a good place to dump the remaining body parts, but apparently did not find a spot to his liking. They made it back to Pensacola around 6 a.m. on Monday, April 6. With Utter-beck’s body parts still in Vollmer’s trunk, they drove onto the Navy base and reported for duty aboard the Forrestal. When they got off work that day, they drove to a wooded area outside of Pensacola and buried the body parts in several shallow holes. On their drive back into town, they scattered some remaining pieces of evidence in a few dumpsters. B. When Utterbeck failed to report for roll call on Monday, April 6, the Navy took note of his unauthorized absence but did not further investigate until later that month, when Utterbeck’s mother called his division commander to tell him that she had not heard from her son since the first weekend in April — when he had traveled to Warner Robins with two shipmates. Inquiries aboard the Forrestal led Navy personnel to Hittson and Vollmer. When questioned about Utterbeck’s whereabouts, they confirmed that they had gone to Vollmer’s parents’ house over the April 3 weekend with Utterbeck, but they claimed that they dropped him off at a bar in Pensacola sometime in early morning hours of Monday, April 6. On April 27, 1992, the Naval Investigative Service issued a missing persons alert for Utter-beck, and on May 5 he was declared a Navy deserter. . On June 16, 1992, Utterbeck’s torso was discovered by loggers who were clearing the wooded property near Vollmer’s parents’ house. The loggers called the Houston County Sheriffs Office, who unearthed the torso and sent it to the state crime lab in Atlanta. The autopsy did not reveal the victim’s identity. Upon hearing about the dead body, the local woman, who had months earlier written down Vollmer’s license plate, called the sheriffs office. The plate number she had written down was off by one digit, so the Houston County officials were not able to immediately trace the car to Vollmer. On June 23,1992, after receiving no new leads on Utterbeck’s whereabouts, Navy investigators broadcast a request to other law enforcement agencies for information regarding any unidentified bodies matching Utterbeck’s general description. The Houston County Sheriffs Office responded the same day, informing the Navy that they had unearthed the remains of a white male matching Utterbeck’s characteristics approximately two miles from Vollmer’s parents’ house, with a time of death estimated sometime in early April. Investigators from Houston County and the Navy interviewed Hittson on June 25, 1992. Hittson initially stuck to his story— that he and Vollmer had dropped Utter-beck off at a bar sometime early Monday morning — but after being confronted with the investigators’ suspicions that they had found Utterbeck’s dismembered body, Hittson confessed that he and Vollmer had murdered Utterbeck and buried him there. In a taped statement given to the investigators — which was later played for the jury — Hittson described the murder, dismemberment, and disposal of the body parts in detail. After confessing, Hittson led investigators to the spot outside Pensacola where the remaining body parts were buried. He also told the investigators where to find the baseball bat, which he and Vollmer had stashed in the rafters of the shed at Vollmer’s parents’ house. Hittson was then taken into custody by the Houston County Sheriffs Office. That same day, Vollmer was arrested in Houston County, at his parents’ house. The next day, investigators executed search warrants for Vollmer’s car and his parents’ house. They found traces of blood and .22 caliber ammunition in the trunk of Vollmer’s car. They recovered the .22 pistol, the aluminum bat, the hacksaw, the piece of slate Hittson and Vollmer used during the dismembering, and other various pieces of evidence from the house, and they found traces of blood on the kitchen floor and baseboard. II. A. A Houston County grand jury returned an indictment on June 30, 1992, charging Hittson and Vollmer with four counts: Count One, malice murder; Count Two, armed robbery; Count Three, aggravated assault; and Count Four, possession of a firearm during the commission of a crime. At arraignment, both defendants pled not guilty, and in September 1992, the Houston County District Attorney filed a notice of the State’s intention to seek the death penalty. The cases against Hittson and Vollmer were severed; at a joint trial, Hittson’s confession, which implicated Vollmer, would technically be introduced against Hittson only, but the spillover effect would deny Vollmer a fair trial. The case against Hittson would be tried first. Hittson’s trial began on February 25, 1993, in the Superior Court of Houston County. During the guilt phase, Hittson’s recorded confession formed the framework for the State’s case, with various experts and lay witnesses confirming the gory details Hittson related and a raft of gruesome autopsy photos showing Utterbeck’s partially-decomposed torso and severed head, hands, and feet. The State rested its case after three days, and Hittson did not put on a defense to contest guilt. On Saturday, February 27, 1993, the jury found Hittson guilty on all counts. The penalty phase of the trial began Monday, March 1. Under Georgia law, to sentence a convicted murderer to death, the jury must return a unanimous verdict finding at least one statutorily defined aggravating factor. See O.C.G.A. § 17-10-31(a). The State, relying on the evidence presented in the guilt phase, pointed to two such factors in support of a death sentence: the murder was committed during the commission of an aggravated battery, see id. § 17-10-30(b)(2), and the murder “was outrageously or wantonly vile, horrible, or inhuman in that it involved torture, depravity of mind, or an aggravated battery to the victim,” see id. § 17-10-30(b)(7). The State did not put on any new evidence during the penalty phase. A Georgia jury must also consider mitigating factors in deciding whether to return a death sentence. Id. § 17-10-30(b). Even if the jury finds an aggravating factor, they may still return a life sentence, with no requirement that they explain their reasons for doing so. Head v. Tho-mason, 276 Ga. 434, 436, 578 S.E.2d 426, 429 (2003). Hittson’s defense against a death sentence took a day and a half; it consisted of the testimony of twenty lay witnesses who either knew Hittson before he joined the Navy or worked with him or supervised him on the Forrestal. The witnesses portrayed Hittson as a good-natured guy who, though somewhat dim-witted, was a hard worker and was eager to please. His shipmates, some of whom shared an apartment with him in Pensacola, testified that Hitt-son drank frequently and heavily and would sometimes do stupid things when drunk. The defense also elicited testimony that Hittson grew up in an unaffeetionate home and was constantly in search of affirmation from others, he occasionally grew depressed because he thought no one could love him, and he would go to great lengths to be accepted by others. Several of his shipmates testified that he was impressionable and gullible and would generally go along with whatever he thought people wanted from him. His supervisors had similar assessments — e.g., “he was just a kid that needed some guidance and direction,” and “he had a very fragile personality and he wanted to fit in.” Lt. Cornelius Mapp, Hittson’s division officer, explained that “Hittson’s the type of person that you can convince that he’d done anything.” In his assessment, Hittson wasn’t capable of such a brutal murder— “If he’s guilty, I think he’s guilty of being in the presence of a crime and he didn’t report it.” In contrast to painting Hittson as the easily-duped kid with a dependent personality, the defense sought to portray Vollmer as a violent sociopath who had plotted the murder and manipulated Hittson into helping him carry it out. Several witnesses testified that Vollmer was intelligent and domineering; one shipmate explained that he “wanted people to think he was in control,” and a friend of Vollmer’s explained that he “liked to play with people’s heads.” The defense submitted letters written by Vollmer that showed him to be arrogant and violent. Shipmates described Vollmer as a “violent guy” who “likes to hold a grudge” and was known to keep his bulletproof vest and aluminum bat in his car and occasionally carry a sawed-off shotgun under his trench coat. The defense laid out evidence that Vollmer had been contemplating murder long before the April 3 weekend. On three or four occasions, Vollmer borrowed a shipmate’s copy of a documentary describing forensic techniques used to detect and solve murders. He read books about murder. He told several people, both before and after the murder, that the best way to dispose of a body was to cut it up. In one of his letters, Vollmer described a detailed plan to murder the boyfriend of a woman he used to be romantically involved with. Regarding Utterbeck, a few witnesses testified that Vollmer did not like him and, prior to the murder, had told shipmates who had disagreements with Utterbeck that he would “take care of’ him for them. No one ever identified a concrete motive for either Vollmer or Hitt-son, but the inference the defense team wanted the jury to draw was that Vollmer had been thinking about killing someone for quite a while, and on that April weekend, Hittson “was led by Mr. Vollmer to do this out of some perverse or demented fantasy that Mr. Vollmer had entertained.” According to the defense’s theory, it was no surprise that someone like Hittson would be vulnerable to manipulation by someone like Vollmer. The narrative they sought to create was “that basically away from the co-defendant, [Hittson] was a pretty harmless guy ... he drank a lot, but, basically, he was sort of a needy kind of harmless little guy, and that Mr. Vollmer was the brains of this operation and basically manipulated [Hittson] into doing something that he would have never done.” One witness during the penalty phase described Hittson as Vollmer’s “sidekick” — his “dog.” In the words of another witness, “Vollmer was, you know, he liked to tell somebody what to do, and Hittson was the kind of guy, you know, if you’re his friend and ... you tell him something to do, he’ll do it. So Vollmer had somebody to tell what to do and somebody to do it, and Hittson had somebody who ... would tell him what to do.” To further distinguish Hittson from Vollmer, the defense presented testimony that, after that April weekend, their relationship deteriorated. Vollmer continued to be thé “same old guy.” He jokingly told his friends that he had killed Utter-beck and told shipmates that if they shot someone, to shoot them in the heart instead of the head, because head wounds bleed too much. In comparison, Hittson stopped hanging around Vollmer after the murder — they even got in a fight shortly before they were arrested — and Hittson became withdrawn and depressed and began to drink even more. One night after some heavy drinking, Hittson confessed to his best friend, Steven Nix, that Utterbeck “wasn’t ever coming back.” When asked if Hittson appeared remorseful during this conversation, Nix responded, “[l]ooking back now, maybe, he might have been.” To rebut Nix’s testimony that Hittson might have been remorseful, the State called Dr. Robert Storms, the psychologist the State had employed to examine Hitt-son prior to trial, to testify to statements made by Hittson during the examination. Prior to trial, the defense team had Hitt-son examined by a psychologist and psychiatrist and were considering using some of the experts’ findings as mitigation evidence during the penalty phase. To preserve their right to present this evidence, a few weeks before the trial began they filed a Notice of Intent of Defense to Raise Issue of Insanity or Mental Incompetence. See Ga. UnifiSuper. Ct. R. 31.4 (1993) (now Rule 31.5). To allow the State to counter the defense experts’ findings, the trial court granted the State’s motion for an order requiring Hittson to submit to an examination by an expert of the State’s choosing, Dr. Storms. Hittson’s attorneys were allowed to attend the examination, and Hittson signed a form waiving his Miranda rights before talking to Dr. Storms. During the interview, Hittson described Utterbeck as a “hillbilly” and an “asshole.” The defense team eventually decided not to put on any expert opinion testimony of Hittson’s mental condition; instead, they stuck to the lay testimony they had already presented and rested their ease. Nonetheless, the State, in rebuttal, proffered in camera the testimony Dr. Storms would give, as a “lay” witness, about Hittson’s description of Utterbeck-ostensibly to counter Nix’s testimony that Hittson was remorseful. The defense team strenuously objected to the proffer on the grounds that Hittson’s waiver of his Miranda right against self-incrimination was limited to the admission of Dr. Storms’s opinion testimony to rebut the defense experts’ opinions. The court overruled the objection, and Dr. Storms testified before the jury in accordance with his proffer. After stating his name, position, and reason for interviewing Hittson, Dr. Storms testified as follows: Q Now, in the course of ... your interview with [Hittson] did you, at any time, ask him about his opinion, or to give some statement about Mr. Conway Ut-terbeck? A Yes. I wanted to find out about that relationship. Q All right. And if you would, please, state what this defendant said about Conway. A Well, at one point he stated that Mr. Utterbeck was a “hillbilly,” and at another point he stated that he was an “asshole.” Hittson’s attorneys did not cross examine Dr. Storms or present any evidence in surrebuttal. In its closing argument to the jury, the State made reference to the “hillbilly” and “asshole” comments again: [Yjou’ve heard one of the defense witnesses talk about, well, as I think about it now he was remorseful. I think he was remorseful. Well, members of the jury, there’s your remorse. (Referring to easel.) As early, or as late, rather, as three weeks ago this is this defendant’s response when asked about Conway Utterbeck being an innocent human being. Conway was a hillbilly, he was an asshole. Is that remorse? What does your common sense tell you? What does reason tell you? In the defense’s closing argument, Hitt-son’s attorney discounted the comments and sought to mitigate their impact by pointing out Hittson’s cooperation with investigators — he confessed, led investigators to the body parts, and told them where to find the bat. In other words, regardless of how Hittson described Utter-beck, he was clearly overcome with guilt about what he had done — why else would he have confessed and aided investigators in making the case against him? The court charged the jury with their task — that, in considering whether to impose the death penalty, they unanimously find at least one aggravating factor to exist beyond a reasonable doubt. In explaining the requirements for finding that the murder was “outrageously or wantonly vile, horrible, or inhuman,” the court instructed the jury that they must find that the murder involved either “[1] depravity of mind; or [2] torture of the victim prior to the death of the victim; or [3] aggravated battery to the victim prior to the death of the victim.” See O.C.G.A. § 17-10-30(b)(7). The court further clarified that “[djepravity of mind is a reflection of an utterly corrupt, perverted, or immoral state of mind,” and in deciding whether the murder involved such a mindset, the jury could consider “the actions of the defendant prior to and after the commission of the murder,” including whether the defendant “subjected the body of a deceased victim to mutilation.” The jury took all of the evidence from the guilt phase with them into deliberations, including a picture of Utterbeck before the murder; pictures of Utterbeck’s mutilated torso and severed head, hands, and feet; autopsy photos showing the mutilation in great detail; and a diagram of Vollmer’s parents’ house indicating where Hittson hit Utterbeck with the bat, dragged him into the kitchen, and where he was positioned when Hittson shot him. The jury also had the defense’s exhibits from the penalty phase, including the letters written by Vollmer, several pictures of Hittson with his family and as a child, and an art project Hittson made in school. During deliberations, the jury sent the court two questions aimed at whether a “life sentence” actually meant that Hittson would spend the rest of his life in prison. The court responded to both by repeating its original charge, that a life sentence meant Hittson would “serve the remainder of life in the penitentiary.” After approximately four hours, the jury returned a unanimous death sentence. The aggravating circumstance they found was that the murder was “outrageously or wantonly vile, horrible, or inhuman, in that it involved depravity of mind.” The judge imposed Hittson’s death sentence on March 17,1993. In October 1993, Vollmer pled guilty to the- murder count in exchange for a life sentence. He is currently eligible for parole. B. Hittson appealed his convictions and death sentence to the Georgia Supreme Court, asserting a raft of trial court errors; chief among them was the court’s ruling that allowed Dr. Storms to testify in accordance with his proffer. Hittson’s brief to the Supreme Court reiterated his objection at trial, arguing that, to the extent that he waived his privilege against self-incrimination when he signed the Miranda waiver form and submitted to the court-ordered examination, that waiver was limited to allowing the State to rebut defense expert testimony of his mental condition. Thus, when the trial court allowed Dr. Storms to testify as a lay witness to rebut Hittson’s evidence of remorse, it went beyond the scope of the waiver and violated Hittson’s Fifth Amendment right against compelled self-incrimination. Hittson also argued that, by ordering him to submit to Dr. Storms’s examination without any notice that his statements could be used against him — even if he did not present expert testimony in his own defense — the trial court denied him any meaningful assistance of counsel in connection with the examination, in violation of the Sixth Amendment. Hittson relied on Estelle v. Smith, 451 U.S. 454, 101 S.Ct. 1866, 68 L.Ed.2d 359 (1981), as the legal basis for both arguments. For convenience, we refer to the Fifth and Sixth Amendment violations based on Dr. Storms’s testimony as Hittson’s “Estelle claims.” In October 1994, the Georgia Supreme Court upheld Hittson’s convictions and death sentence. Hittson v. State, 264 Ga. 682, 449 S.E.2d 586 (1994), cert. denied 514 U.S. 1129, 115 S.Ct. 2005, 131 L.Ed.2d 1005 (1995). In rejecting his Fifth Amendment claim, the court explained that Hitt-son voluntarily waived his privilege against self-incrimination when he signed the Miranda form prior to the examination. Id. at 684-85, 449 S.E.2d 586, 449 S.E.2d at 591-92. And the court found no Sixth Amendment violation because the trial court adequately instructed defense counsel on the scope and nature of the examination and allowed them to observe it and voice objections if necessary. Id. at 685, 449 S.E.2d at 592. C. In December 1995, Hittson petitioned the Superior Court of Butts County, Georgia, for a writ of habeas corpus. See O.C.G.A. § 9-14-42. His petition alleged ineffective assistance of counsel “at virtually every critical stage before and during trial.” The ineffective-assistance claim before us in the immediate appeal — that Hittson’s trial counsel, in the penalty phase of his trial, failed to present mitigating expert testimony regarding his background and mental condition — was among the allegations. The petition also raised a “protective” Brady claim, which generally alleged that the State withheld exculpatory evidence but did not identify the evidence. Hittson’s petition did not include his Estelle claims — because the Georgia Supreme Court rejected the claims on direct appeal, he was precluded from raising them on collateral attack absent an intervening change in the law. See Bruce v. Smith, 274 Ga. 432, 434, 553 S.E.2d 808, 810 (2001). The Superior Court held a two-day evi-dentiary hearing on Hittson’s petition in October 1997. At the close of the hearing, the court denied Hittson’s protective Brady claim because he failed to come forward with any exculpatory evidence the State had withheld at trial. In an order issued in July 1998, the court shaped Hittson’s ineffective-assistance allegations into eight discrete claims and rejected all of them under the standard set forth in Strickland v. Washington, 466 U.S. 668, 687, 104 S.Ct. 2052, 2064, 80 L.Ed.2d 674 (1984). In October 1998, Hittson applied to the Georgia Supreme Court for a certificate of probable cause to appeal (“CPC”), pursuant to O.C.G.A. § 9-14-52. He took issue with the Superior Court’s denial of five of his ineffective-assistance claims. Finding that his arguments lacked “arguable merit,” the Georgia Supreme Court denied the CPC in September 2000. See Ga. Sup. Ct. R. 36. While Hittson’s CPC application was pending, the Georgia Supreme Court decided Nance v. State, 272 Ga. 217, 526 S.E.2d 560 (2000), in which the court explicitly overruled its decision in Hittson’s direct appeal on the following point: [W]hen a defendant must submit to a court-ordered mental health examination because he wishes to present expert mental health testimony at his trial, the State expert may only testify in rebuttal to the testimony of the defense expert or to rebut the testimony of the defendant himself. To the extent Hittson v. State authorized a State expert to testify in response to lay witness testimony that the defendant was remorseful, it is overruled. Id. at 220, 220 n. 2, 526 S.E.2d at 565, 565 n. 2 (citations omitted). Hittson did not seek leave to amend his CPC application to ask the Georgia Supreme Court to consider the effect of Nance on his Estelle claims (which he had not raised in the Butts County Superior Court). However, after the Supreme Court denied his CPC application, Hittson filed a motion for reconsideration, asking the high court to consider the Estelle claims in light of Nance. The Supreme Court summarily denied the motion in January 2001, and the United States Supreme Court denied certiorari review in May 2001, Hittson v. Turpin, 532 U.S. 1052, 121 S.Ct. 2193, 149 L.Ed.2d 1025 (2001). III. A. In January 2002, Hittson petitioned the United States District Court for the Mid-die District of Georgia for a writ of habeas corpus, pursuant to 28 U.S.C. § 2254, setting aside his convictions and death sentence. The petition included most of the claims he presented to the Georgia Supreme Court on direct appeal and to the Butts County Superior Court in his habeas petition, including the Estelle claims, several ineffective-assistance claims, and the protective Brady claim. To allow Hittson to flesh out his Brady claim, the District Court ordered the State to turn over the District Attorney’s file on the Utterbeck murder prosecution. When Hittson’s ha-beas counsel reviewed the file, they discovered a 1991 Navy psychiatric report, which diagnosed Vollmer with Antisocial Personality Disorder, and two letters Vollmer had written from jail that touched on certain aspects of the murder. Because Hittson had not litigated Brady claims based on this evidence in the Butts County Superior Court, the District Court stayed further proceedings to allow Hittson to exhaust the newfound Brady claims in state court. B. Accordingly, in July 2005, Hittson returned to the Butts County Superior Court, filing a second habeas petition. The petition included two new Brady claims, one based on Vollmer’s psychiatric report and the other on the post-arrest letters he wrote from the jail. Hittson also resubmitted his claim that the admission of Dr. Storms’s lay testimony violated his Fifth Amendment right against self-incrimination. Under Georgia law, a state prisoner may only bring a successive habeas petition that raises claims “which could not reasonably have been raised in the original or amended petition.” O.C.G.A. § 9-14-51. Hittson alleged that his new petition was his first opportunity to bring these claims because (a) he didn’t have access to the Brady material until the federal district court ordered discovery of the District Attorney’s file and (b) res judicata barred his Fifth Amendment claim at the time he prosecuted his first habeas petition — it was only after the Supreme Court in Nance overruled its decision rejecting his Fifth Amendment claim in his direct appeal that he was able to assert the claim in a habeas petition. The Superior Court disagreed. Without conducting an evidentiary hearing, the court held that all of Hittson’s claims could have been presented while he was prosecuting his first habeas petition and were thus barred as successive. The Georgia Supreme Court granted a certificate of probable cause to appeal from this decision, vacated the Superior Court’s decision, and remanded the case with instructions that the court conduct an evidentiary hearing. With the benefit of a two-day hearing, the Superior Court again denied habeas relief, in January 2009. In a somewhat convoluted opinion, the court rejected Hitt-son’s Fifth Amendment claim on three separate grounds: (1) The claim was barred by res judicata because the Georgia Supreme Court rejected it on direct appeal, and even though Nance overruled that decision, Nance did not apply retroactively because “Nance did not set forth a new rule of constitutional dimension, but merely narrowed an existing rule of criminal procedure.” (2) The claim was barred by res judicata because, even if Nance applied retroactively, the Supreme Court denied Hittson’s CPC application, and motion for reconsideration of that denial, after Nance was decided. (3) Even if the Fifth Amendment claim was properly before the court, and even if the admission of Dr. Storms’s testimony violated Hittson’s privilege against self-inerimination, it was harmless error in light of the overwhelming evidence in support of the jury’s death sentence. The Superior Court rejected the Brady claims on alternative grounds too. It held that the claim based on Vollmer’s psychiatric report was procedurally defaulted because Hittson’s trial counsel or the attorneys who represented him in his first habeas proceeding could have obtained the report from a source other than the Houston County District Attorney through the exercise of reasonable diligence and Hittson had not shown cause and resulting prejudice to excuse his failure to raise the claim on direct appeal or in his first habeas petition. Even so, the court held that both Brady claims failed on the merits because the Yollmer psychiatric report and Yollmer’s jailhouse letters were cumulative of the mitigation evidence presented during the penalty phase and the evidence supporting a death sentence was overwhelming; thus, even when considered cumulatively, the “withheld” evidence did not create a reasonable probability of a different result. Hittson again sought a certificate of probable cause from the Georgia Supreme Court. He argued that (1) none of his claims could have been raised at any point before he filed his second habeas petition; (2) that the allowance of Dr. Storms’s testimony violated his Fifth and Sixth Amendment rights and the error was not harmless; and (3) that the suppressed Brady material, considered either separately or cumulatively, created a reasonable probability that the jury would have returned a life sentence. The Georgia high court concluded that these arguments lacked arguable merit and summarily denied Hittson’s CPC application in October 2010. The United States Supreme Court denied cer-tiorari review in June 2011. Hittson v. Humphrey, — U.S.-, 131 S.Ct. 3038, 180 L.Ed.2d 858 (2011). C. In July 2011, Hittson returned to the District Court and amended his habeas petition to include his now-exhausted Brady claims. In November 2012, the District Court granted the writ, setting aside Hitt-son’s death sentence based on his Estelle claims. The court found that the trial court’s admission of Dr. Storms’s testimony violated Hittson’s Fifth and Sixth Amendment rights and that the Georgia Supreme Court’s decision on direct appeal (the decision Nance overruled) unreasonably applied Estelle and its progeny in concluding otherwise. Hittson, 2012 WL 5497808, at *30-35. The District Court then applied the harmless-error standard from Brecht v. Abrahamson, 507 U.S. 619, 637-38, 113 S.Ct. 1710, 1721-22, 123 L.Ed.2d 353 (1993), and concluded that Dr. Storms’s testimony had a “substantial and injurious effect” on the jury’s death sentence deliberations. Hittson, 2012 WL 5497808, at *37-40. Accordingly, the court vacated Hittson’s sentence and ordered that the State conduct a new penalty-phase proceeding or impose a lesser sentence. The District Court denied the rest of Hittson’s claims, but granted a COA for his Brady claims. This court then expanded the COA to include one of his ineffective-assistance-of-counsel claims. IV. “We review de novo the grant or denial of a writ of habeas corpus by a district court.” Muhammad v. Sec’y, Fla. Dep’t of Corr., 733 F.3d 1065, 1071 (11th Cir.2013). Thus, we review Hittson’s Estelle claims, Brady claims, and ineffective-assistance claim using the standard established by 28 U.S.C. § 2254, as amended by the Antiterrorism and Effective Death Penalty Act of 1996 (“AEDPA”), Pub.L. No. 104-132, 110 Stat. 214 — the same standard the District Court used. A. Under AEDPA, if a petitioner’s claims have been “adjudicated on the merits in State court,” a federal court cannot grant habeas relief unless the state court’s adjudication of the claims (1) “was contrary to, or involved an unreasonable application of, clearly established Federal law, as determined by the Supreme Court of the United States,” or (2) “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). A state-court decision is “contrary to” federal law if it either “applies a rule that contradicts the governing law set forth in [Supreme Court] cases” — e.g., by applying the wrong legal standard to a particular claim — or “confronts a set of facts that are materially indistinguishable from a decision of [the Supreme] Court and nevertheless arrives at a [different] result.” Williams v. Taylor, 529 U.S. 362, 405-06, 120 S.Ct. 1495, 1519-20, 146 L.Ed.2d 389 (2000). A state-court decision is an “unreasonable application” of Supreme Court precedent if the state court “correctly identifies the governing legal rule but applies it unreasonably to the facts of a particular prisoner’s case.” Id. at 407-08, 120 S.Ct. at 1520. “[A]n unreasonable application of federal law is different from an incorrect application of federal law.” Id. at 410, 120 S.Ct. at 1522. “[S]o long as fairminded jurists could disagree on the correctness of the state court’s decision,” a federal court cannot grant habeas relief. Harrington v. Richter, 562 U.S. 86, 131 S.Ct. 770, 786, 178 L.Ed.2d 624 (2011) (citation and quotation marks omitted). Finally, “AEDPA instructs that, when a federal habeas petitioner challenges the factual basis for a prior state-court decision rejecting a claim, the federal court may overturn the state court’s decision only if it was ‘based on an unreasonable determination of the facts in light of the evidence presented in the State court proceeding.’” Burt v. Titlow, — U.S. -, 134 S.Ct. 10, 15, 187 L.Ed.2d 348 (2013) (quoting 28 U.S.C. § 2254(d)(2)). In such cases, “[t]he prisoner bears the burden of rebutting the state court’s factual findings ‘by clear and convincing evidence.’ ” Id. (quoting 28 U.S.C. § 2254(e)(1)). Like the “unreasonable application” standard in § 2254(d)(1), “a state-court factual determination is not unreasonable merely because the federal ha-beas court would have reached a different conclusion in the first instance.” Wood v. Allen, 558 U.S. 290, 301, 130 S.Ct. 841, 849, 175 L.Ed.2d 738 (2010). “[E]ven if reasonable minds reviewing the record might disagree about the finding in question ... that does not suffice to supersede the [state] court’s determination.” Id. (alterations and quotation marks omitted). B. Thus, AEDPA requires that our analysis of Hittson’s constitutional claims be grounded in the Georgia courts’ adjudication of those claims. Because we are considering multiple claims that were addressed by multiple state courts, it is useful at the outset to explain which state-court decisions we look to for purposes of AEDPA review. Section 2254(d) requires that we defer to the state court’s adjudication of a petitioner’s constitutional claims. As this court has observed, “the state court’s ‘adjudication on the merits,’ which triggers our review under [§ 2254], is the same ‘adjudication of the claim’ that we review for its application of federal law.... Therefore, the highest state court decision reaching the merits of a habeas petitioner’s claim is the relevant state court decision” we review under ÁEDPA. Newland v. Hall, 527 F.3d 1162, 1199 (11th Cir.2008); see also Harris v. Reed, 489 U.S. 255, 263, 109 S.Ct. 1038, 1043, 103 L.Ed.2d 308 (1989) (instructing federal courts to look to the “last state court rendering a judgment in the case” for the state court’s reasons for rejecting a claim). In Hittson’s case, the last state court to pass on the merits of the relevant claims was the Georgia Supreme Court, when it summarily denied a certificate of probable cause to appeal from the Butts County Superior Court’s denial of Hittson’s first, and then second, habeas petition. See Newland, 527 F.3d at 1199. Because the denial of the right to appeal by the state’s highest court does not always constitute an adjudication on the merits, we briefly describe Georgia’s habeas appeals process to reveal why the Georgia Supreme Court’s denial of a CPC in this ease constituted an adjudication on the merits. Georgia habeas petitioners are required to obtain a certificate of probable cause from the Georgia Supreme Court before appealing a superior court decision denying relief. O.C.G.A. § 9-14-52(b). The standard for granting a CPC is set forth in Rule 36 of the Georgia Supreme Court Rules, which provides that “[a] certificate of probable cause to appeal a final judgment in a habeas corpus case involving a criminal conviction will be issued where there is arguable merit.” Ga. Sup.Ct. R. 36 (emphasis added); see also Sears v. Humphrey, 294 Ga. 117, 117, 751 S.E.2d 365, 368 (2013) (explaining that a CPC denial rests on the Supreme Court’s conclusion that a claim lacks “arguable merit”). “In order for the Supreme Court to consider fully the request for a certificate,” § 9-14-52(b) directs the superior court clerk to transfer the record and transcript of the proceedings below to the Supreme Court. As the Supreme Court has explained, the purpose of transcribed eviden-tiary hearings in the superior courts is, at least in part, “to assist the parties in preparing and opposing the application for a certificate of probable cause to appeal” and “to assist the [Supreme] Court in considering the application.” Edwards v. State, 288 Ga. 459, 460, 707 S.E.2d 335, 336 (2011). Therefore, in denying Hittson’s CPC applications to appeal the denial of his first and second habeas petitions, the Supreme Court was not exercising discretionary review akin a denial of a petition for certio-rari review. See generally Ga. Sup.Ct. R. 34. Instead, the court was required to grant a CPC if it found arguable merit to any of the arguments in the application. In concluding that Hittson’s claims lacked arguable merit, the Supreme Court had the benefit of the record from prior proceedings, the transcripts of the hearings held on his habeas petitions, and briefing on the merits of his constitutional claims. Such a standard clearly constitutes an adjudication on the merits for AEDPA purposes. See Johnson v. Williams, — U.S. -, 133 S.Ct. 1088, 1097, 185 L.Ed.2d 105 (2013) (“A judgment is normally said to have been rendered on the merits only if it was delivered after the court heard and evaluated the evidence and the parties’ substantive arguments.” (alteration, emphasis, and quotation marks omitted)). While the Georgia high court denied each CPC without explaining why it found Hittson’s arguments to be meritless, there is no AEDPA requirement that a state court explain its reasons for rejecting a claim; “Section 2254(d) applies even where there has been a summary denial.” Cullen v. Pinholster, — U.S. -, 131 S.Ct. 1388, 1402, 179 L.Ed.2d 557 (2011). “When a federal claim has been presented to a state court and the state court has denied relief, it may be presumed that the state court adjudicated the claim on the merits in the absence of any indication or state-law procedural principles to the contrary.” Richter, 562 U.S. at -, 131 S.Ct. at 784-85. Our task in these situations is to review the record before the Georgia Supreme Court to “determine what arguments or theories supported or, as here, could have supported, the state court’s decision.” Id. at-, 131 S.Ct. at 786. Hittson may only obtain federal habeas relief “by showing there was no reasonable basis for the state court to deny relief.” Id. at-, 131 S.Ct. at 784. With this standard in mind, we turn to Hittson’s constitutional claims. V. We begin with the two Estelle claims. The first Estelle claim is that Hittson’s Fifth Amendment right against self-incrimination was denied when the trial court, over Hittson’s objection, permitted Dr. Storms to testify before the jury in conformance with his in camera proffer. The second claim is that the trial court deprived Hittson of any meaningful assistance of counsel when it ordered him to submit to an examination by Dr. Storms after waiving his Miranda rights. The State now concedes the denial of Hittson’s Fifth and Sixth Amendment rights and, accordingly, does not challenge the District Court’s conclusion, reached under § 2254(d)(1), that the Georgia Supreme Court unreasonably applied Estelle in denying both claims. But that does not end our inquiry. We must decide whether these violations, which yielded Dr. Storms’s testimony, prejudiced Hittson’s defense in the penalty phase so to entitle Hittson to habeas relief. A. In § 2254 proceedings, federal courts must evaluate constitutional errors under the harmless-error standard articulated in Brecht v. Abrahamson, 507 U.S. 619, 113 S.Ct. 1710, 123 L.Ed.2d 353 (1993). As Brecht explained, “[federal] habeas petitioners may obtain plenary review of their constitutional claims, but they are not entitled to habeas relief based on trial error unless they can establish that it resulted in ‘actual prejudice.’ ” Id. at 637, 113 S.Ct. at 1722. To find “actual prejudice,” a federal habeas court must conclude that the error “had substantial and injurious effect or influence in determining the jury’s verdict.” Id. (quoting Kotteakos v. United States, 328 U.S. 750, 776, 66 S.Ct. 1239, 1253, 90 L.Ed. 1557 (1946)). The District Court concluded that Dr. Storms’s testimony had a “substantial and injurious effect” on the jury’s deliberations over Hittson’s sentence. We review this decision de novo; therefore, we review the record to determine if Dr. Storms’s testimony had a “substantial or injurious effect” on the jury’s deliberations. In conducting this review, “[t]he inquiry [is not] merely whether there was enough to support the result, apart from the phase affected by the error. It is rather, even so, whether the error itself had substantial influence.” Kotteakos, 328 U.S. at 764-65, 66 S.Ct. at 1248. If there is “more than a reasonable possibility that the error contributed to the conviction or sentence,” then the error is not harmless. Mansfield v. Sec’y, Fla. Dep’t of Corr., 679 F.3d 1301, 1313 (11th Cir.2012). Because Georgia law requires a jury to unanimously find at least one statutorily defined aggravating factor to return a death sentence, O.C.G.A. § 17-10-31, “habeas relief is warranted in this case if we believe even one of the jurors who voted in favor of the death penalty likely was substantially influenced” by the error, Duest v. Singletary, 997 F.2d 1336, 1339 (11th Cir.1993) (per curiam). Because the error in Hittson’s trial resulted in the improper admission of evidence, we must measure the impact of Dr. Storms’s testimony on the jury in light of the body of evidence before them at the time. See Kotteakos, 328 U.S. at 764, 66 S.Ct. at 1248 (“[Courts] must take account of what the error meant to [the jury], not singled out and standing alone, but in relation to all else that happened.”). We analyze this impact by “looking at several factors, including ‘the importance of the witness’[s] testimony in the prosecution’s case, whether the testimony was cumulative, the presence or absence of evidence corroborating or contradicting the testimony of the witness on material points, ... and, of course, the overall strength of the prosecution’s case.’ ” Mason v. Allen, 605 F.3d 1114, 1123-24 (11th Cir.2010) (per curiam) (quoting Delaware v. Van Arsdall, 475 U.S. 673, 684, 106 S.Ct. 1431, 1438, 89 L.Ed.2d 674 (1986)). B. We begin with the jury’s sentence. The jury found, after deliberating for four hours, that Hittson should be sentenced to death on account of the “outrageously or wantonly vile, horrible, or inhuman” nature of the murder. See O.C.G.A. § 17-10-30(b)(7). The trial court instructed the jury that, in order to rely on this aggravating factor, it must find that the murder was both “outrageously or wantonly vile, horrible, or inhuman” and that it involved “depravity of mind; or torture to the victim prior to the death of the victim; or aggravated battery to the victim prior to the death of the victim.” As the court explained it, “[djepravity of mind is a reflection of an utterly corrupt, perverted, or immoral state of mind,” and in evaluating Hittson’s mindset, the jury could consider his actions “prior to and after the commission of the murder,” including whether he “subjected the body of a deceased victim to mutilation.” It is abundantly clear that the jury could have relied on this aggravating factor in the absence of Dr. Storms’s testimony. The jury heard Hittson’s taped confession, during which he calmly described his role in the murder: how he found Utterbeck (who, according to Vollmer, was planning to ambush them) asleep in the living room, hit Utterbeck in the head with a baseball bat three times, dragged him to the kitchen so as not to make a mess on the living room carpet, and shot him in the forehead while he begged for his life. After stripping Utterbeck’s corpse and leaving it to bleed out on the kitchen floor, Hittson and Vollmer left to grab a bite to eat. Upon their return, they meticulously sawed off Utterbeck’s head, hands, and feet, and at least one of them castrated him, skinned his penis and buttocks, and cut out his rectum. They tossed Utterbeck’s mutilated torso in a shallow grave, spent the better part of a day cleaning his blood off the interior of the house, and headed back to Pensacola with his severed head, hands, and feet in the trunk — stopping off to say “bye” to Vollmer’s sister-in-law on the way out of town. Clearly, the crime itself justified the jury’s conclusion that Hittson carried out an “outrageously or wantonly vile, horrible, or inhuman” murder with “depravity of mind.” While Brecht “does not require a showing that but for the error the jury would have rendered a verdict in favor of the defendant,” Duest, 997 F.2d at 1338, the overwhelming amount of evidence that supports the aggravating factor found by the jury — particularly the post-mortem dismemberment and mutilation, which the court explicitly mentioned in its charge— convinces us that Dr. Storms’s testimony did not meaningfully influence the jury’s reliance on the “vile, horrible, and inhuman” aggravating factor. See Mansfield, 679 F.3d at 1313 (“[T]he erroneous admission of evidence is likely to be harmless under the Brecht standard where there is significant corroborating evidence.... ”). In reaching the opposite conclusion, the District Court explained: Dr. Storms’ testimony that Hittson called Utterbeck an asshole and a hillbilly certainly helped the State prove depravity of mind. The jury was instructed that they could consider Hittson’s actions after the commission of the crime. Dr. Storms’ testimony was the only evidence that months after the crime, and with Vollmer completely out of the picture, Hittson possessed a “corrupt” or “immoral state of mind.” Hittson, 2012 WL 5497808, at *40. We flatly reject the District Court’s conclusion that the jury found Hittson’s statements to Dr. Storms, made long after the crime, to be probative of the “vile, horrible, and inhuman” nature of the murder or his “utterly corrupt, perverted, or immoral” state of mind. The trial court told the jury that, in evaluating Hittson’s mindset during the murder, they should consider whether he committed aggravated battery, torture, or mutilation. The jury heard, from Hittson’s own mouth, a detailed description of how he and Vollmer cut Utter-beck up and stuffed him into garbage bags, and the State paraded a raft of grisly photos before the jury to give life to Hitt-son’s words. In light of the trial court’s instructions and the overwhelming evidence supporting the jury’s aggravating factor, we do not believe that the jury, in faithfully executing their duty, gave any weight to Dr. Storms’s testimony in concluding that Hittson carried out the “vile, horrible, and inhuman” murder with “depravity of mind.” But the aggravating factor merely allowed the jury to return a death sentence. They could have still sentenced Hittson to life imprisonment based on mitigating circumstances, and so we must also assess the effectiveness of Dr. Storms’s testimony as a rebuttal of Hittson’s mitigation evidence — the purpose for which it was admitted. Hittson claims that “Dr. Storms’s testimony was absolutely devastating to Mr. Hittson’s defense ... that Mr. Hittson was remorseful, burdened and ashamed.” Hittson Appellee Br. at 26-27. This argument overstates both the strength of the “remorse” evidence and the ability of Dr. Storms’s testimony to rebut that evidence. Over the course of two days and twenty witnesses, the only mention of remorse during the penalty phase came from Hitt-son’s best friend on the Forrestal, Steven Nix. Nix testified that, when Hittson told him Utterbeck was never coming back, Hittson seemed “kind-of sad, kind-of down, kind-of depressed.” Doc. 74-9, at 43. When asked if Hittson seemed remorseful, Nix responded, “Maybe.... Looking back now, maybe, he might have been.... I didn’t notice it at the time.” Id. at 48. The only other evidence of Hittson’s remorse during trial came from one of the detectives who interviewed Hittson. He testified, during the guilt phase, that prior to confessing: I felt that [Hittson] had possibly been involved in something that he was not extremely proud of, something that he had been a part of that he might not have necessarily been the instigator of; and that there was a possibility that he had been at the wrong place at the wrong time; and that this was something that I wasn’t real sure that he could, he could live with; that it might would be to his best interest