dissenting.
The majority has determined that portraying a male teenager as fat, lazy, and choosing liposuction to avoid working out has the same effect on a jury as portraying a male teenager as the sufferer of a genetic disorder that causes underdeveloped testes, gender identity disturbance, and size-DD breasts that required a double mastectomy at age thirteen. Because I conclude that these two scenarios have the potential to yield very different outcomes, I dissent.
There are several points of disagreement between myself and the majority. First, unlike the majority, I do not believe that we need only assume that counsel in this case was deficient; applying Supreme Court and Sixth Circuit precedent, I believe that it is clear that Cornwell’s attorney’s representation at the penalty phase was deficient. As the Supreme Court has stated numerous times, if “counsel ha[ve] not ‘fulfilled] their obligation to conduct a thorough investigation of the defendant’s background,’ ” then counsel’s representation is deficient. See, e.g., Wiggins v. Smith, 539 U.S. 510, 522, 123 S.Ct. 2527, 156 L.Ed.2d 471 (2003) (quoting Williams v. Taylor, 529 U.S. 362, 396, 120 S.Ct. 1495, 146 L.Ed.2d 389 (2000)) (second alteration in Wiggins); see also Dickerson v. Bagley, 453 F.3d 690, 693 (6th Cir.2006) (“[T]he Supreme Court ... has made it clear and come down hard on the point that a thorough and complete mitigation investigation is absolutely necessary in capital cases.”). Moreover, as we have explained, “a partial, but ultimately incomplete, mitigation investigation does not satisfy Strickland’s requirements” for effective counsel. Dickerson, 453 F.3d at 695; see also Johnson v. Bagley, 544 F.3d 592, 602 (6th Cir.2008) (“[A]n unreasonably truncated mitigation investigation is not cured simply because ... some evidence was placed before the jury.”). As the majority begrudgingly admits, in a death penalty case, a thorough mitigation investigation requires counsel to investigate, at the very least, the known medical history of the defendant, including hospitalizations. Maj. Op. at 407; see also Dickerson, 453 F.3d at 693-94.
It is undisputed that counsel in this case was aware that Cornwell as a thirteen-year-old teenager was hospitalized for a double mastectomy, but counsel never bothered to locate those medical records and provide them to Dr. Eisenberg. Under Supreme Court precedent, this is a blatant violation of counsel’s duty. Dickerson, 453 F.3d at 693-94. Given counsel’s failure to satisfy this straightforward requirement, I am unsure why the majority believes “[i]t could be argued ... that a finding that counsel was not deficient would not be an unreasonable application of clearly established law.” Maj. Op. at 408. The majority attempts to ameliorate trial counsel’s failure of the mandatory duty to investigate medical records by asserting that, “trial counsel otherwise did a fairly thorough investigation.” Maj. Op. at 407. However, as our case law makes clear, an “otherwise thorough investigation,” id., is not the same thing as the thorough investigation required by Strickland-, counsel are not given a free pass to *418violate a specific duty in one area of investigation if they diligently investigate other areas, see Dickerson, 453 F.3d at 695 (“[A] partial, but ultimately incomplete, mitigation investigation does not satisfy Strickland’s requirements.”); see also id. (noting that in Harries v. Bell, 417 F.3d 631 (6th Cir.2005), this court concluded that counsel’s performance was deficient when they failed to investigate, among other things, mental health history, “even though counsel had conducted various interviews of the petitioner’s family and acquaintances and had sought other information, including two competency evaluations”). Such a rule would be tantamount to giving a police officer a free pass for violating his duty not to shoot an unarmed suspect, so long as he complied with all other duties he owed to that suspect. Therefore, I conclude that Cornwell’s trial counsel was deficient.
Second, I cannot agree with the majority’s baseless assertion that Cornwell has not shown prejudice resulting from trial counsel’s deficiency. To prove prejudice, a defendant must show that “there is a reasonable probability that, but for counsel’s unprofessional errors, the result of the proceeding would have been different.” Strickland v. Washington, 466 U.S. 668, 694, 104 S.Ct. 2052, 80 L.Ed.2d 674 (1984). I think that Cornwell has met his burden on this issue.
At the penalty phase, Cornwell was portrayed by his family as a fat, lazy person who took the easy way out of situations, evidenced by his choice to undergo “cosmetic” surgery instead of working out to lose weight. See, e.g., Joint Appendix (“J.A.”) at 2335, 2348, 2349 (Penalty Phase Tr. 5/21/97 at 73, 80, 87) (testimony of LaShonda Cornwell that “[Cornwell] was lazy, you know,” that “[Cornwell] was still like lazy,” even after his surgery, and that “it was like [Cornwell] took his lazy time to do stuff’); J.A. at 2412 (Penalty Phase Tr. 5/21/97 at 150) (testimony of Beverly Corn-well Terry repeatedly referring to Corn-well’s surgery as “cosmetic”). No one utilized and emphasized this image more than the prosecutor. At closing argument, the prosecutor stated: “Did [Cornwell] work out with weights, run, watch what you eat, what all the rest of us have to try and do? No, he went for liposuction. He had a fat reduction. For God’s sake, [Cornwell]’s lazy.” J.A. at 2542 (Penalty Phase Tr. 5/21/97 at 274).
Had Cornwell’s medical records been given to Dr. Eisenberg, the expert hired to aid Cornwell’s mitigation case, he likely would have realized that Cornwell may be suffering from Klinefelter Syndrome, a genetic disorder that causes weight gain, enlarged breasts, language issues, and underdeveloped genitals.1 The fact that the *419post-conviction expert, Dr. Haskins, a forensic psychologist just like Dr. Eisenberg, realized this possibility after reviewing the medical records indicates a strong likelihood that Dr. Eisenberg would have reached this realization. With this knowledge, Dr. Eisenberg could have corrected the image of Cornwell being portrayed by informing the jury that Klinefelter Syndrome was the likely cause of Cornwell’s various problems, not laziness. This information would have allowed the jury to view Cornwell in a much more sympathetic light — not as a teenager who had been lazy and taken the easy road in his life, but as a teenager who suffered the burdens of a genetic disease that he could not control and for which he never received a diagnosis, let alone treatment. Furthermore, evidence of Klinefelter Syndrome would reduce Cornwell’s blameworthiness in a way that the weight-related evidence alone did not. Because this genetic-disorder image creates “a mitigation ease that bears no relation to” the case of laziness presented, Rompilla v. Beard, 545 U.S. 374, 393, 125 S.Ct. 2456, 162 L.Ed.2d 360 (2005), I believe that Cornwell has met his burden of showing prejudice.
The majority contends that “[t]he state courts could reasonably reject an assumption that jurors blame teenagers for their own weight problems and somehow consider those who are overweight or lazy or have cosmetic surgery more deserving of the death penalty than those who are thin or energetic or have surgery related to medical conditions.” Maj. Op. at 409. I find this reasoning odd, given the fact that the prosecutor in this case — a person who likely has significant experience and expertise in regard to what persuades juries— appeared to assume that the jury would be heavily swayed by this fact. Why else would the prosecutor emphasize the issue so conspicuously in his closing argument?2
Because I believe that the jury, as the prosecution hoped, likely viewed Cornwell less sympathetically and placed more culpability on Cornwell than it would have had he not been portrayed as overweight and lazy, I cannot accept the majority’s rationale on this issue. Looking at the case as a whole,
although [I] suppose it is possible that a jury could have heard [all the evidence] and still have decided on the death penalty, that is not the test. It goes without saying that the undiscovered mitigating *420evidence, taken as a whole, might well have influenced the jury’s appraisal of [Cornwell’s] culpability, and the likelihood of a different result if the evidence had gone in is sufficient to undermine confidence in the outcome actually reached at sentencing.
Rompilla, 545 U.S. at 393, 125 S.Ct. 2456 (emphasis added) (internal quotation marks and citations omitted). Therefore, I would hold that Cornwell has proven his claim of ineffective assistance of counsel and that the state-court decision to the contrary was objectively unreasonable. I would reverse the district court’s denial of habeas relief.
Furthermore, I would hold that the district court abused its discretion by denying Cornwell’s motion for a genetic expert. A request for an expert is a discovery request; thus a district court’s denial of a motion for appointment of an expert is reviewed for abuse of discretion. Lott v. Coyle, 261 F.3d 594, 602 (6th Cir.2001). “A district court may, in the context of a habeas proceeding, permit discovery, provided that the habeas petitioner presents specific allegations showing reason to believe that the facts, if fully developed, may lead the district court to believe that federal habeas relief is appropriate.” Id.
As explained above, I believe that a diagnosis of Klinefelter Syndrome would have a reasonable probability of affecting the outcome of the penalty phase and rendering the state-court finding of no prejudice objectively unreasonable because (1) having a genetic disorder is itself a strong mitigator and was a subject not addressed at the penalty phase, (2) a mitigation case centered on a genetic disorder, as opposed to an overweight individual who is lazy by nature, would induce much more sympathy from the jury, and (3) Klinefelter Syndrome could indeed reduce Cornwell’s blameworthiness, something that the weight-based evidence did not accomplish. Thus, Cornwell has met his burden of showing that “the facts, if fully developed, may lead the district court to believe that federal habeas relief is appropriate.” Id. Therefore, I would hold, at the very least, that Cornwell is entitled to a genetic expert to determine whether he has Klinefel-ter Syndrome and that the district court abused its discretion by holding to the contrary. I respectfully dissent.
. The National Institute of Child Health and Human Development (“Institute”), an organization created by Congress in 1962 to investigate human development throughout the entire life process, states that "Klinefelter syndrome, also known as the XXV condition, is a term used to describe males who have an extra X chromosome in most of their cells. Instead of having the usual XY chromosome pattern that most males have, these men have an XXY pattern.” National Institute of Child Health and Human Development, Klinefelter Syndrome, http:/ /www. nichd.nih.gov/health/topics/ldinefelter— syndrome.cfm (last visited March 6, 2009). The Institute also notes that, "[a]s XXY males enter puberty, they often don't make as much testosterone as other boys. This can lead to a taller, less muscular body, less facial and body hair, and broader hips than other boys. As teens, XXY males may have larger breasts, weaker bones, and a lower energy level than other boys.” Id. Such boys can also have “some kind of language problem, such as learning to talk late, trouble using language to express thoughts and needs, problems reading, and trouble processing what they hear.” Id. Although XXY boys tend to be “quieter, less self-confident, less active, and more helpful and obedient than other boys,” *419during adolescence, "XXY males ... may struggle in school and sports, meaning they may have more trouble 'fitting in' with other kids." Id.
. I agree with the majority that "[o]ur system of justice finds its foundation in the belief that average citizens can and will weigh all the evidence presented to them, follow the law, and reach a well-reasoned verdict.” Maj. Op. at 409. (emphasis added). However, this very idea presumes that a jury is given all the evidence needed to reach a well-reasoned verdict; before one can even begin to talk about whether a jury verdict is well-reasoned, one must first review the evidence presented to the jury. It is this threshold inquiry that we are confronted with in this case: Whether the jury was given all the information it needed to reach a well-reasoned verdict. The answer to this question, in my opinion, is no. Thus, I do not find fault with the jury, but rather I find fault with the wholly inadequate mitigation case that was presented to the jury. To suggest that such a conclusion is "at odds with the guarantees of the Sixth Amendment and the underlying principles of our judicial system,” id. at 409, necessarily implies that all jurists who order new trials based on a failure to present proper evidence to the jury are at odds with the Sixth Amendment. If there is any distrust in this arena, it is a distrust of verdicts rendered by juries who, through fault of counsel or judges, have not been given all the necessary and proper information to weigh in order to reach a verdict. This is a distrust that does not offend the principles of our judicial system, but rather protects those vital principles.