(Slip Opinion)              OCTOBER TERM, 2023                                       1

                                       Syllabus

         NOTE: Where it is feasible, a syllabus (headnote) will be released, as is
       being done in connection with this case, at the time the opinion is issued.
       The syllabus constitutes no part of the opinion of the Court but has been
       prepared by the Reporter of Decisions for the convenience of the reader.
       See United States v. Detroit Timber & Lumber Co., 

.


SUPREME COURT OF THE UNITED STATES

                                       Syllabus

 THORNELL, DIRECTOR, ARIZONA DEPARTMENT OF
            CORRECTIONS v. JONES

CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR
                  THE NINTH CIRCUIT

       No. 22–982.      Argued April 17, 2024—Decided May 30, 2024
Respondent Danny Lee Jones was convicted of the premeditated first-
  degree murders of Robert and Tisha Weaver and the attempted pre-
  meditated murder of Robert’s grandmother Katherine Gumina. Ari-
  zona law at the time required the trial court to “impose a sentence of
  death” if it found “one or more” statutorily enumerated “aggravating
  circumstances” and “no mitigating circumstances sufficiently substan-
  tial to call for leniency.” Ariz. Rev. Stat. Ann. §13–703(E). The trial
  court found three aggravating circumstances that applied to both Rob-
  ert’s and Tisha’s murders: Jones committed multiple homicides, §13–
  703(F)(8); he was motivated by “pecuniary” gain, §13–703(F)(5); and
  the murders were “especially heinous, cruel or depraved,” §13–
  703(F)(6). The trial court found an additional aggravating circum-
  stance with respect to Tisha’s murder: she was a young child, §13–
  703(F)(9). The trial court also concluded that Jones had established
  four mitigating circumstances: long-term substance abuse, drug and
  alcohol impairment at the time of the murders, head trauma, and
  childhood abuse. 9 Record 2465. The court concluded that these miti-
  gating circumstances were “not sufficiently substantial to outweigh
  the aggravating circumstances,” so it sentenced Jones to death. Ibid.
  The Arizona Supreme Court affirmed after “review[ing] the entire rec-
  ord” and “independently weighing all of the aggravating and mitigat-
  ing evidence presented.” 

, 

.
     Jones later sought state postconviction review on the theory that de-
  fense counsel was ineffective, but the Arizona courts rejected Jones’s
  claims. Jones next filed a federal habeas petition in District Court and
  reasserted his ineffective-assistance-of-counsel claims. The District
  Court held an evidentiary hearing but ultimately concluded that Jones
2                           THORNELL v. JONES

                                    Syllabus

    could not show prejudice because the additional information he pre-
    sented “ ‘barely. . . alter[ed] the sentencing profile presented to the sen-
    tencing judge.’ ” Jones v. Schriro, 

 (quoting
    Strickland v. Washington, 

). The Ninth Circuit re-
    versed, but this Court vacated that judgment and remanded for the
    Ninth Circuit to determine whether, in light of Cullen v. Pinholster,
    

, it had been proper to consider the new evidence pre-
    sented at the federal evidentiary hearing. See Ryan v. Jones, 

. On reconsideration, the Ninth Circuit again granted habeas re-
    lief. The panel held that it was permissible to consider the new evi-
    dence and concluded that there was a “ ‘reasonable probability’ ” that
    “Jones would not have received a death sentence” if that evidence had
    been presented at sentencing. Jones v. Ryan, 

, 1137.
    Ten judges dissented from the denial of en banc review. One dissent,
    joined by eight judges, asserted that the Ninth Circuit panel flouted
    Strickland by crediting “questionable, weak, and cumulative mitiga-
    tion evidence” as “enough to overcome . . . weight[y] . . . aggravating
    circumstances.” 

.
Held: The Ninth Circuit’s interpretation and application of Strickland
 was in error. Pp. 7–16.
    (a) To succeed on his ineffective-assistance-of-counsel claim, Jones
 must show that counsel provided a “deficient” performance that “prej-
 udiced” him. Strickland, 

. Jones can show prejudice
 only if “there is a reasonable probability that, absent [counsel’s] errors,
 the sentencer . . . would have concluded that the balance of aggravat-
 ing and mitigating circumstances did not warrant death.” 

.
 “A reasonable probability is a probability sufficient to undermine con-
 fidence in the outcome. That requires a substantial, not just conceiv-
 able, likelihood of a different result.” Pinholster, 

 (ci-
 tation and internal quotation marks omitted). To determine whether
 a prisoner satisfies this standard, a court must “consider the totality
 of the evidence before the judge or jury”—both mitigating and aggra-
 vating. Strickland, 

.
    The Ninth Circuit departed from these well-established rules in at
 least three ways. First, it failed adequately to take into account the
 weighty aggravating circumstances. Second, it applied a strange Cir-
 cuit rule that prohibits a court in a Strickland case from assessing the
 relative strength of expert witness testimony. Third, it held that the
 District Court erred by attaching diminished persuasive value to
 Jones’s mental health conditions. See 52 F. 4th, at 1129. Contrary to
 the Ninth Circuit’s suggestion, Eddings v. Oklahoma, 

,
 permits a sentencer to find mitigating evidence unpersuasive.
    Jones argues that a habeas petitioner is entitled to relief whenever
 he or she “presents substantial evidence of the kind that a reasonable
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                               Syllabus

sentencer might deem relevant to the defendant’s moral culpability.”
Brief for Respondent 14. This rule is squarely at odds with the estab-
lished understanding of prejudice under Strickland, which requires a
“reasonable probability” of a different result. Where aggravating fac-
tors greatly outweigh mitigating evidence, there may be no “reasona-
ble probability” of a different result. Pp. 7–9.
   (b) Turning to the issue of prejudice in this case, the mitigating evi-
dence Jones presented at the federal evidentiary hearing “would
barely have altered the sentencing profile presented to the sentencing
judge,” and it is insufficient to show prejudice. Strickland, 

. Pp. 9–13.
     (1) Jones presented evidence that, he claims, shows he suffers
from various mental illnesses. But Arizona courts had already heard
testimony that Jones “suffers from a major mental illness,” likely a
“form of Bipolar Affective Disorder.” 4 Record 1070; 10 id., at 2567.
And they declined to give this evidence much weight because Jones did
not “establish a causal connection between his alleged mental illness
and his conduct on the night of the murders.” 

, 

. Jones’s new evidence did not fix that problem because
Jones’s experts provided no real link between Jones’s disorders and
the murders. Pp. 9–10.
     (2) Next, Jones introduced evidence that he suffers from cognitive
impairment caused by physical trauma that he suffered during his
mother’s pregnancy, at birth, and later in life. But Arizona courts had
already heard extensive evidence about Jones’s head trauma and cog-
nitive impairment and did not find this evidence sufficient to warrant
leniency. 

 The little evidence Jones added at his evidentiary
hearing at most corroborates the testimony that the Arizona courts
already credited, and it would thus provide little benefit. Pp. 11.
     (3) In federal court, Jones also alleged sexual abuse by his grand-
father and physical abuse by his second stepfather. But this evidence
would not help either. Again, the Arizona courts had heard about
many other instances of childhood abuse but concluded they did not
warrant leniency, primarily because the abuse appeared unconnected
to the murders. 185 Ariz., at 490–491, 917 P. 2d, at 219–220; 9 Record
2465. The new allegations are likewise not causally connected and,
at any rate, are uncorroborated. Arizona courts would give such self-
reported and uncorroborated evidence “little . . . mitigating weight.”
State v. Sharp, 

, 

. Pp. 12–13.
     (4) Finally, Jones produced evidence of substance abuse, but his
history of substance abuse was “well-documented” at the time of sen-
tencing, and the Arizona Supreme Court gave this fact “some mitigat-
ing weight,” 

, 

. There is no reasonable
chance Arizona courts would reach a different result on essentially the
4                         THORNELL v. JONES

                                  Syllabus

    same evidence. P. 13.
       (c) The weakness of Jones’s mitigating evidence contrasts sharply
    with the strength of the aggravating circumstances. These circum-
    stances—multiple homicides, cruelty, pecuniary motivation, and mur-
    der of a child—are given great weight in Arizona. The Arizona Su-
    preme Court has repeatedly held that one or more of these aggravating
    circumstances outweighed mitigation evidence—even evidence that
    was “not insubstantial.” State v. Hampton, 

, 

. Conversely, Jones and his amici identify no cases in
    which the Arizona Supreme Court has vacated the judgment of death
    in a case involving multiple murders—let alone all of the aggravating
    circumstances present here. The absence of such a case strongly sug-
    gests that Jones has no reasonable probability of escaping the death
    penalty. Pp. 13–14.
       (d) Contrary to the Ninth Circuit’s conclusion, “the Strickland prej-
    udice analysis conducted by the Supreme Court” in other cases, 52
    F. 4th, at 1131, does not support resentencing here. In those cases,
    defense counsel introduced little, if any, mitigating evidence at the
    original sentencing, and the aggravating circumstances were weaker.
    By contrast, Jones started with much more mitigation evidence, and
    the aggravating circumstances present here are weightier. Had the
    Ninth Circuit engaged in the analysis required by Strickland, it would
    have affirmed the decision of the District Court denying habeas relief.
    Pp. 14–16.

, reversed and remanded.

  ALITO, J., delivered the opinion of the Court, in which ROBERTS, C. J.,
and THOMAS, GORSUCH, KAVANAUGH, and BARRETT, JJ., joined. SO-
TOMAYOR, J., filed a dissenting opinion, in which KAGAN, J., joined. JACK-
SON, J., filed a dissenting opinion.
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                             Opinion of the Court

     NOTICE: This opinion is subject to formal revision before publication in the
     United States Reports. Readers are requested to notify the Reporter of
     Decisions, Supreme Court of the United States, Washington, D. C. 20543,
     [email protected], of any typographical or other formal errors.


SUPREME COURT OF THE UNITED STATES
                                   _________________

                                   No. 22–982
                                   _________________


        RYAN THORNELL, DIRECTOR, ARIZONA
          DEPARTMENT OF CORRECTIONS,
             PETITIONER v. DANNY LEE
                     JONES
 ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF
            APPEALS FOR THE NINTH CIRCUIT
                                 [May 30, 2024]

  JUSTICE ALITO delivered the opinion of the Court.
  In this case, we review a decision of the Ninth Circuit or-
dering the resentencing of a defendant who, in order to steal
a gun collection, committed three gruesome killings, includ-
ing the cold-blooded murder of a 7-year-old girl. The Ninth
Circuit held that the defendant’s Sixth Amendment right to
the effective assistance of counsel was violated during the
sentencing phase of his capital trial. In reaching this con-
clusion, the Ninth Circuit substantially departed from the
well-established standard articulated by this Court in
Strickland v. Washington, 

 (1984). Among
other things, the Ninth Circuit all but ignored the strong
aggravating circumstances in this case. As a result, we
must reverse the judgment below.
                            I
                           A
  Thirty-two years ago, Danny Lee Jones murdered Robert
Weaver, his 7-year-old daughter Tisha Weaver, and his
grandmother Katherine Gumina. Jones knew that Robert
2                     THORNELL v. JONES

                       Opinion of the Court

owned a $2,000 gun collection, and after spending a day
drinking and talking with Robert, Jones decided he wanted
to steal the guns. He grabbed a baseball bat, beat Robert
into unconsciousness, and headed indoors to find the collec-
tion.
   Once inside, Jones encountered Gumina, who was watch-
ing television, and Tisha, who was coloring in a workbook
before heading to bed. Jones struck Gumina hard enough
to crack her skull, leaving her unconscious on the living
room floor. Tisha apparently watched Jones attack her
great-grandmother and ran to hide under her parents’ bed.
Marks on the carpet show that Jones dragged the girl out
from under the bed before beating her hard enough “to cre-
ate a wound several inches wide, extending from her left
ear to her left cheek.” State v. Jones, 

,

 (1996). Jones then asphyxiated Tisha
with a pillow.
   Jones next began loading Robert’s guns into Gumina’s
car. At that point, Robert regained consciousness. “Blood
smears at the scene showed that [Robert] attempted to run
from” Jones, but Jones “struck [him] in the head several
more times. The last blow . . . was delivered while [Robert]
knelt helplessly on the floor of the garage.” 9 Appellant’s
Excerpts of Record in No. 18–99005 (CA9), p. 2449 (Record).
Jones then skipped town with the guns, using them to pay
for a trip to Las Vegas.
   A short time later, Robert’s wife came home from work
and discovered the gruesome scene. She called 911, but the
first responders found that Robert and Tisha were already
dead. Gumina lived for 17 months before succumbing to her
injuries. Before Gumina died, Jones was charged with two
counts of premeditated first-degree murder and one count
of attempted premeditated first-degree murder, and a jury
found him guilty on all three charges.1
——————
 1 Arizona charged Jones before Gumina’s death and elected not to
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                        Opinion of the Court

                               B
   After Jones was convicted, the trial court proceeded to
sentencing. Under Arizona law at the time, the court was
required to “impose a sentence of death” if it found “one or
more” statutorily enumerated “aggravating circumstances”
and “no mitigating circumstances sufficiently substantial to
call for leniency.” Ariz. Rev. Stat. Ann. §13–703(E) (1993).
   The trial court found three aggravating circumstances
that applied to both Robert’s and Tisha’s murders. First,
Jones committed multiple homicides “during the commis-
sion of the offense.” §13–703(F)(8). Second, he was moti-
vated by “pecuniary” gain, namely, Robert’s guns. §13–
703(F)(5). And third, the murders were “especially heinous,
cruel or depraved.” §13–703(F)(6). With respect to Tisha’s
murder, the court found an additional aggravating circum-
stance: She was a young child. §13–703(F)(9).
   The trial court also heard mitigating evidence. The
presentence report noted that Jones was abused as a child,
began using drugs and alcohol at age 13, suffered brain
trauma at ages 9 and 18, and had received “psychiatric
treatments” as a child. 4 Record 1086–1088. Jones’s second
stepfather, Randy, described Jones’s troubled personal life.
He testified that Jones’s father and first stepfather were
physically abusive, that Jones’s grandfather and uncle had
introduced him to drugs as a preteen, and that Jones had
suffered several head injuries that left him with “con-
stan[t]” headaches. 9 id., at 2522–2526.
   Jones’s counsel also submitted a report by and solicited
testimony from Dr. Jack Potts, a court-appointed forensic
psychiatrist who was later described by counsel as essen-
tially “part of the defense team.” 7 id., at 1831. Dr. Potts
identified several “mitigating factors” that he thought war-
ranted leniency. 4 id., at 1070–1071. First, he noted that
Jones “was reared in a chaotic and at times grossly hostile
——————
amend the indictment after she died.
4                    THORNELL v. JONES

                      Opinion of the Court

environment where physical abuse was too prevalent.” Id.,
at 1069. “The years he had of a relatively ‘normal’ child-
hood,” Dr. Potts opined, were “too late . . . to counter the
earlier abuse.” Id., at 1070. Second, Dr. Potts suggested
that Jones’s “serious head trauma” potentially “con-
tribut[ed] to his behavior.” Id., at 1068, 1071. Third, he
concluded with a “reasonable degree of medical certainty”
that Jones “suffers from a major mental illness,” likely a
“form of Bipolar Affective Disorder.” Id., at 1070; 10 id., at
2567. Fourth, he thought Jones was “genetic[ally]” predis-
posed to “substance abuse” and speculated that Jones
would not have murdered had he been sober. 4 id., at 1070.
Fifth, Dr. Potts believed that Jones felt “remorse and re-
sponsibility” and that he had the “potential for rehabilita-
tion.” Id., at 1070–1071.
   From this evidence, the trial court concluded that Jones
had established four mitigating circumstances: (1) Jones
suffered from long-term substance abuse; (2) that problem
may be caused by genetic factors and head trauma; (3) he
was under the influence of alcohol and drugs at the time of
the murders; and (4) he was abused as a child. 9 id., at
2465. The court concluded that these circumstances were
“not sufficiently substantial to outweigh the aggravating
circumstances,” so it sentenced Jones to death. Ibid. The
Arizona Supreme Court affirmed after “review[ing] the en-
tire record” and “independently weighing all of the aggra-
vating and mitigating evidence presented.” Jones, 

, 

.
                              C
  Jones sought state postconviction review on the theory
that defense counsel was ineffective. Jones argued that his
attorney should have retained an independent neuropsy-
chologist, rather than relying on Dr. Potts. The state court
denied this claim because it “remember[ed]” that Dr. Potts
“was a very good expert” at trial and “was defense oriented.”
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                          Opinion of the Court

7 Record 1950. Jones also claimed that trial counsel failed
to make a timely request for neurological or neuropsycho-
logical testing. But after holding an evidentiary hearing on
this claim, the state court rejected it on the merits. Jones
then unsuccessfully sought review in the Arizona Supreme
Court. Order in State v. Jones, No. CR–00–0512–PC (Feb.
15, 2001); 1 Record 186.
                             D
  Jones next filed a habeas petition in Federal District
Court and reasserted his ineffective-assistance-of-counsel
claims. See 

. The District Court held an
evidentiary hearing but ultimately concluded that Jones
could not show prejudice because the additional infor-
mation he presented “ ‘barely . . . alter[ed] the sentencing
profile presented to the sentencing judge.’ ” Jones v.
Schriro, 

 (Ariz. 2006) (quoting
Strickland, 

). The court reached this con-
clusion based on its assessment of “the credibility of the
parties’ witnesses,” including witnesses introduced by the
State to undercut Jones’s claims. 

.
The Ninth Circuit reversed. See Jones v. Ryan, 

 (2009). But this Court vacated that judgment and re-
manded for the Ninth Circuit to determine whether, in light
of Cullen v. Pinholster, 

 (2011), it had been
proper to consider the new evidence presented at the fed-
eral evidentiary hearing. See Ryan v. Jones, 

(2011).
  On reconsideration, the Ninth Circuit again granted ha-
beas relief. The panel held that it was permissible to con-
sider the new evidence 2 and concluded that there was a
——————
  2 The panel reasoned that the postconviction review court had not

reached the issue of prejudice, so it could review the issue de novo. Fur-
ther, “Jones satisfied the standard for an evidentiary hearing pursuant
to §2254(e)(2)” because he “exercised diligence in pursuing [his] claims
in state court.” Jones v. Ryan, 

, 1123 (CA9 2022). Arizona
6                       THORNELL v. JONES

                         Opinion of the Court

“reasonable probability” that “Jones would not have re-
ceived a death sentence” if that evidence had been pre-
sented at sentencing. Jones v. Ryan, 

 (CA9 2021). The panel’s lengthy opinion made no
mention of the aggravating factors, and it did not consider
the State’s rebuttal evidence.
  Arizona sought en banc review. The Ninth Circuit denied
the State’s petition, but the panel amended its opinion to
mention the aggravating circumstances and to rebuke the
District Court for “weigh[ing] the testimony of [competing]
experts against each other.” Jones v. Ryan, 

,
1128 (2022).
  Ten judges dissented from the denial of en banc review.
Judge Ikuta, joined by two other judges, argued that the
panel should have deferred to the state postconviction re-
view court on the Strickland prejudice inquiry. Judge Ben-
nett, joined by eight others, assumed without deciding that
the panel could consider the new evidence. But he asserted
that the panel flouted Strickland by crediting “questiona-
ble, weak, and cumulative mitigation evidence” as “enough
to overcome . . . weight[y] . . . aggravating circumstances.”
52 F. 4th, at 1155 (dissenting opinion). If not corrected,
Judge Bennett wrote, the panel’s errors would enable
“courts to improperly grant sentencing relief to capital de-
fendants who have been convicted of the most horrific
crimes.” Id., at 1137.
  We granted certiorari to review the Ninth Circuit’s inter-
pretation and application of Strickland. 

(2023).



——————
does not challenge either determination. See Tr. of Oral Arg. 22; Brief
for Petitioner 20, n. 8. So we do not decide whether the Ninth Circuit’s
interpretation of either the postconviction review court’s decision or
§2254(e)(2) is correct.
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                      Opinion of the Court

                               II
   Jones claims that his Sixth Amendment right to the ef-
fective assistance of counsel was violated during the sen-
tencing phase of his capital trial. To succeed on such a
claim, a defendant must show that counsel provided a “de-
ficient” performance that “prejudiced” him. Strickland, 

. When an ineffective-assistance-of-counsel
claim is based on counsel’s performance at the sentencing
phase of a capital case, a defendant is prejudiced only if
“there is a reasonable probability that, absent [counsel’s]
errors, the sentencer . . . would have concluded that the bal-
ance of aggravating and mitigating circumstances did not
warrant death.” 

. “A reasonable probability is a
probability sufficient to undermine confidence in the out-
come. That requires a substantial, not just conceivable,
likelihood of a different result.” Pinholster, 

 (citation and internal quotation marks omitted). This
standard does not require a defendant to show that it is
more likely than not that adequate representation would
have led to a better result, but “[t]he difference” should
matter “only in the rarest case.” Strickland, 

. To determine whether a prisoner satisfies this stand-
ard, a court must “consider the totality of the evidence be-
fore the judge or jury”—both mitigating and aggravating.

.
   The Ninth Circuit departed from these well-established
rules in at least three ways. First, it failed adequately to
take into account the weighty aggravating circumstances in
this case. As noted, the panel’s initial opinion did not men-
tion those circumstances at all. After the State petitioned
for rehearing and 10 judges voted to grant the petition, the
panel issued an amended opinion that at least mentioned
the aggravating circumstances, but it failed to give them
the weight that they would almost certainly be accorded by
an Arizona sentencing judge.
   Second, the Ninth Circuit applied a strange Circuit rule
8                    THORNELL v. JONES

                      Opinion of the Court

that prohibits a court in a Strickland case from assessing
the relative strength of expert witness testimony. See 52
F. 4th, at 1128–1129. This rule is clearly unsound. Deter-
mining whether a defense expert’s report or testimony
would have created a reasonable probability of a different
result if it had been offered at trial necessarily requires an
evaluation of the strength of that report or testimony. And
where a prosecution expert has expressed a contrary opin-
ion, it is hard to see how a court could decide how much
weight to give the defense expert without making a compar-
ative analysis.
   Third, the Ninth Circuit held that the District Court
erred by attaching diminished persuasive value to Jones’s
mental health conditions because it saw no link between
those conditions and Jones’s conduct when he committed
the three murders. See id., at 1129. The Ninth Circuit
seemed to suggest that this conclusion was supported by
Eddings v. Oklahoma, 

 (1982), but that is not
so. Eddings held that a sentencer may not “refuse to con-
sider . . . any relevant mitigating evidence.” 

. It
did not hold that a sentencer cannot find mitigating evi-
dence unpersuasive. See 

 at 114–115 (emphasizing that
“[t]he sentencer . . . may determine the weight to be given
relevant mitigating evidence”).
   Picking up what he takes to be the implications of these
three features of the Ninth Circuit’s analysis, Jones argues
that a habeas petitioner is entitled to relief whenever he or
she “presents substantial evidence of the kind that a rea-
sonable sentencer might deem relevant to the defendant’s
moral culpability.” Brief for Respondent 14. Whether or
not this rule represents a fair extrapolation of the Ninth
Circuit’s reasoning, it is squarely at odds with the estab-
lished understanding of prejudice, which requires a “rea-
sonable probability” of a different result. Imagine a defend-
ant with the worst possible aggravating circumstances, say,
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                      Opinion of the Court

multiple, vulnerable victims; torture; a lengthy record of vi-
olent crime; no remorse; and a vow to kill again if given the
chance. According to Jones, if the defense is able to show
that trial counsel failed to produce any mitigating evidence
that can be characterized as “substantial,” the defendant
must be resentenced. But in such a case, where the aggra-
vating factors greatly outweigh the mitigating evidence,
there may be no “reasonable probability” of a different re-
sult. Thus, Jones’s argument is squarely inconsistent with
Strickland.
                              III
  With the proper understanding of Strickland in mind, we
turn to the prejudice issue in this case. Most of the mitigat-
ing evidence Jones presented at the federal evidentiary
hearing was not new, and what was new would not carry
much weight in Arizona courts. Conversely, the aggravat-
ing factors present here are extremely weighty. As a result,
there is no reasonable probability that the evidence on
which Jones relies would have altered the outcome at sen-
tencing.
                             A
  We begin with the mitigating evidence. In the District
Court, Jones introduced evidence of (1) mental illness,
(2) cognitive impairment caused by a history of head
trauma, (3) childhood abuse, and (4) substance abuse.
Jones claims that this evidence requires resentencing, but
as the District Court aptly observed, this evidence “would
barely have altered the sentencing profile presented to the
sentencing judge,” and it is insufficient to show prejudice.
Strickland, 466 U. S., at 699–700.
                             1
  Jones claims that his newly proffered evidence shows
that he suffers from “PTSD, AD/HD, mood disorder, [and]
bipolar depressive disorder.” Brief for Respondent 45. But
10                   THORNELL v. JONES

                      Opinion of the Court

it is not reasonably likely that this evidence would have re-
sulted in a different sentence.
   Arizona courts had already received testimony that Jones
“suffers from a major mental illness,” likely a “form of Bi-
polar Affective Disorder.” 4 Record 1070; 10 id., at 2567.
Yet they declined to give this evidence much weight because
Jones did not “establish a causal connection between his al-
leged mental illness and his conduct on the night of the
murders.” Jones, 

, 

; accord,
State v. Prince, 

, 

(2011) (discounting poor mental health when no “expert
could establish [the defendant’s] mental state on the night
of the shootings”); State v. Boggs, 

, 

 (2008) (same).
   Jones’s new evidence did not fix that problem. One of
Jones’s experts reiterated that Jones has a mood disorder,
but he did not express an opinion on whether that disorder
affected Jones on the night of the murders. 4 Record 823–
825. Two experts diagnosed Jones with PTSD, but neither
testified that he experienced such symptoms at the time of
the murders. 2 

 at 506–508; 

 at 451–453. Likewise,
no expert linked Jones’s AD/HD to the murders; indeed, one
of the State’s witnesses testified that there is no link be-
tween that disorder and violence. 

. Because none
of Jones’s experts provided a real link between Jones’s dis-
orders and the murders, their testimony would have done
him little good in the Arizona courts. See State v. Poyson,

, 

 (2020) (failure
to link mitigating evidence to the crime may diminish its
weight); State v. Stuard, 

, 

 (1993) (“[E]vidence of causation is required
before mental impairment can be considered a significant
mitigating factor”).
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                      Opinion of the Court

                                2
   Next, Jones introduced evidence that he suffers from cog-
nitive impairment caused by physical trauma that he suf-
fered during his mother’s pregnancy, at birth, and later in
life. Brief for Respondent 44. But there is no reason to
think that this evidence would have meaningfully changed
how the state court viewed the case.
   Arizona courts had already heard extensive evidence
about Jones’s head trauma and cognitive impairment. For
instance, the sentencing court learned that Jones’s biologi-
cal father knocked his mother down stairs when she was
pregnant with him, 4 Record 1067, 9 id., 2523, that his birth
was traumatic, ibid., and that he was physically abused by
his first stepfather, 4 id., at 1067. The sentencing court
knew that Jones had been knocked unconscious as the re-
sult of three falls during childhood and adolescence and a
mugging in his late teens. Id., at 1068, 1087; 9 id., at 2526,
2528–2529; 10 id., at 2556–2557, 2569, 2580. It also heard
from Dr. Potts that Jones’s head trauma potentially con-
tributed to his behavior. 4 id., at 1068, 1071. Yet it did not
find this evidence sufficient to warrant leniency. And after
reviewing the same evidence, the Arizona Supreme Court
concurred. Jones, 

, 

 (cred-
iting Dr. Potts’s assumption that Jones had brain damage).
   Jones added little on this issue at his evidentiary hearing.
He alleged a few additional head injuries from car accidents
and fights, but “there is no medical documentation to cor-
roborate any of these injuries.” Jones, 

, and n. 11. And though his experts flagged a handful
of poor test scores and grades, Jones’s IQ and standardized
test scores are mostly average. 2 Record 347, 358–376, 379–
399; 3 id., at 798. This vague evidence at most “corrobo-
rate[s]” testimony the Arizona courts already credited.
Jones, 

, 

. Introducing it
“would have offered an insignificant benefit, if any at all.”
Wong v. Belmontes, 

 (2009) (per curiam).
12                  THORNELL v. JONES

                     Opinion of the Court

                               3
   Jones also alleges significant childhood abuse. Brief for
Respondent 44. Again, however, Arizona courts had heard
much on this topic. They knew that Jones’s father abused
his pregnant mother, that his first stepfather beat both of
them, and that his grandfather introduced him to drugs at
a young age. And they received testimony that any period
of normalcy during Jones’s childhood was “too late” and “not
strong enough to counter the earlier abuse.” 4 Record
1069–1070. They nevertheless concluded that this abuse
did not warrant leniency, primarily because it appeared un-
connected to the murders. Jones, 185 Ariz., at 490–491, 917
P. 2d, at 219–220; 9 Record 2465.
   In federal court, Jones added two new allegations. First,
he asserted that the grandfather who introduced him to al-
cohol also sexually abused him. Second, he claimed that his
second stepfather, Randy, physically abused him. It is not
likely that these allegations would have moved the state
court either.
   The sexual-abuse allegation is entirely uncorroborated.
Jones did not mention it until his federal habeas proceed-
ings. 2 

 at 503–504. And his mother and second stepfa-
ther explained that they “never saw any indication that
[Jones] may have been sexually abused by anyone, nor were
they aware of any sexual perpetrators in the family.” Rec-
ord in No. 2:01–cv–00384 (D Ariz., Feb. 13, 2006), ECF Doc.
172–3, p. 49. Arizona courts would give this self-reported
and uncorroborated evidence “little . . . mitigating weight.”
State v. Sharp, 

, 

(1999); accord, State v. Gerlaugh, 

, 

 (1985).
   Jones’s physical-abuse allegation against Randy is not
much more helpful. Granted, his sister seconded his alle-
gation. 4 Record 982–987. But other record evidence con-
tradicts it. For instance, Jones told Dr. Potts that Randy
                  Cite as: 

 (2024)           13

                      Opinion of the Court

was “quite stern and a disciplinarian yet certainly not phys-
ically abusive.” 

 at 1067–1068 (emphasis added). On
another occasion well before this litigation, Jones said that
“[a]s far as I’m concerned,” Randy “is my real dad[;] he’s the
only one that has treated me good. He has never hit me or
anything.” Id., at 1020 (emphasis added). Given Jones’s
“obvious motive to fabricate,” Arizona courts would view
this abuse allegation with some “skepticism.” State v.
Medrano, 

, 

 (1996); see
also Gerlaugh, 

, 

; State v.
Carriger, 

, 

 (1984).
And even crediting the allegation, it suffers from the same
weakness that led the Arizona courts to discount Jones’s
other abuse allegations: it is not causally connected to the
murders.
                               4
  Finally, Jones points to evidence of substance abuse,
namely, that his grandfather introduced him to drugs and
alcohol when he was “only nine years old.” Brief for Re-
spondent 44. But Jones’s history of substantive abuse was
“well-documented” at the time of sentencing. Jones, 

, 

. The Arizona Supreme
Court, for instance, recounted that “by the time [Jones] was
17 years old, he had used many types of drugs and was an
alcoholic.” Ibid.; see also 4 Record 1086–1088 (presentenc-
ing report noting that Jones began consuming alcohol and
using drugs at 13). And that court gave this fact “some mit-
igating weight.” Jones, 

, 

.
There is no reasonable chance that those courts would
reach a different result on a second look at essentially the
same evidence.
                          B
  The weakness of Jones’s mitigating evidence contrasts
14                  THORNELL v. JONES

                     Opinion of the Court

sharply with the strength of the aggravating circum-
stances. These circumstances—multiple homicides, cru-
elty, pecuniary motivation, and murder of a child—are
given great weight in Arizona. See State v. Garza, 

, 

 (2007) (multiple-homicides ag-
gravator gets “ ‘extraordinary weight’ ”); Poyson, 

, 

 (the cruelty and pecuniary-motiva-
tion aggravators are “particularly weighty”); State v. New-
ell, 

, 

 (2006) (young age
of the victim is a “compelling aggravating circumstanc[e]”
in favor of the death penalty).
   Indeed, in a host of cases, the Arizona Supreme Court has
held that one or more of these aggravating circumstances
outweighed mitigation evidence—even evidence that was
“not insubstantial.” State v. Hampton, 

,

 (2006) (concluding that the multiple-
homicides aggravator outweighed evidence of a “horren-
dous childhood”); see also Poyson, 250 Ariz., at 57–58, 475
P. 3d, at 302–303 (listing several cases in which the multi-
ple-homicides aggravator alone outweighed all mitigating
circumstances); State v. McKinney, 

, 227, 

 (2018) (cruelty and pecuniary-motivation
aggravators outweighed evidence that a defendant had “en-
dured a horrific childhood” and suffered from mental ill-
ness). Conversely, Jones and his amici identify no cases in
which the Arizona Supreme Court has vacated the judg-
ment of death in a case involving multiple murders—let
alone a case involving all of the aggravating circumstances
present here. The absence of such a case strongly suggests
that Jones has no reasonable probability of escaping the
death penalty.
                            IV
  To justify its contrary conclusion, the Ninth Circuit
pointed to “the Strickland prejudice analysis conducted by
the Supreme Court” in “similar cases.” 52 F. 4th, at 1131.
                 Cite as: 

 (2024)           15

                     Opinion of the Court

In these cases, the Ninth Circuit stated, we found prejudice
when counsel failed to present “classic mitigating evi-
dence,” even though the defendants had committed “brutal
crimes.” 

.
   A review of the precedents cited by the Ninth Circuit
shows that they are very different from the case now before
us. In each of the ineffective-assistance-of-counsel cases on
which the Ninth Circuit relied, this Court found that de-
fense counsel introduced little, if any, mitigating evidence
at the original sentencing. See Porter v. McCollum, 

 (2009) (per curiam); Williams v. Taylor, 

, 395–398 (2000); Rompilla v. Beard, 

 (2005); Wiggins v. Smith, 

, 534–
535 (2003). Jones, by contrast, started with much more mit-
igation. And in most of the other cases, the sentencer found
only a few aggravating circumstances. See Porter, 

 (three aggravators, two of which the sentencing
judge thought “were insufficient to warrant death”); Wil-
liams, 

 (one aggravator); Wiggins, 

 (one aggravator). That is a far cry from the
weighty aggravating circumstances present here. Poyson,

, 

.
                         *    *     *
  When a capital defendant claims that he was prejudiced
at sentencing because counsel failed to present available
mitigating evidence, a court must decide whether it is rea-
sonably likely that the additional evidence would have
avoided a death sentence. This analysis requires an evalu-
ation of the strength of all the evidence and a comparison
of the weight of aggravating and mitigating factors. The
Ninth Circuit did not heed that instruction; rather, it down-
played the serious aggravating factors present here and
overstated the strength of mitigating evidence that differed
very little from the evidence presented at sentencing. Had
the Ninth Circuit engaged in the analysis required by
16                 THORNELL v. JONES

                    Opinion of the Court

Strickland, it would have had no choice but to affirm the
decision of the District Court denying habeas relief. We
therefore reverse the judgment of the Court of Appeals and
remand the case for further proceedings consistent with
this opinion.

                                           It is so ordered.
                  Cite as: 

 (2024)              1

                    SOTOMAYOR, J., dissenting

SUPREME COURT OF THE UNITED STATES
                          _________________

                           No. 22–982
                          _________________


       RYAN THORNELL, DIRECTOR, ARIZONA
         DEPARTMENT OF CORRECTIONS,
            PETITIONER v. DANNY LEE
                    JONES
 ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF
            APPEALS FOR THE NINTH CIRCUIT
                         [May 30, 2024]

   JUSTICE SOTOMAYOR, with whom JUSTICE KAGAN joins,
dissenting.
   I agree with the Court that “the Ninth Circuit all but ig-
nored the strong aggravating circumstances in this case.”
Ante, at 1. That was error. As part of the prejudice inquiry
for ineffective-assistance-of-counsel claims, courts must
“consider all the evidence—the good and the bad,” Wong v.
Belmontes, 

 (2009) (per curiam), and must
“reweigh the evidence in aggravation against the totality of
available mitigating evidence,” Wiggins v. Smith, 

 (2003).
   The majority unnecessarily goes further and engages in
the reweighing itself. See ante, at 8–14. The record in this
case is complex, contested, and thousands of pages long. In
light of this “extensive record” and “intricate procedural
history, . . . this is not an appropriate case to reach and set-
tle [a] fact-sensitive issue.” CRST Van Expedited, Inc. v.
EEOC, 

 (2016). That is particularly true
when, as here, the majority in the first instance parses a
complex record containing contested medical diagnoses and
disputed allegations of abuse and trauma.
   “It is not the Court’s usual practice to adjudicate either
legal or predicate factual questions in the first instance.”
2                    THORNELL v. JONES

                   SOTOMAYOR, J., dissenting

Ibid.; see also Cutter v. Wilkinson, 

(2005) (“[W]e are a court of review, not first view”). Because
I would vacate the judgment below and remand for the
Ninth Circuit to consider the full record in the first in-
stance, I respectfully dissent.
                      Cite as: 

 (2024)                     1

                         JACKSON, J., dissenting

SUPREME COURT OF THE UNITED STATES
                               _________________

                               No. 22–982
                               _________________


         RYAN THORNELL, DIRECTOR, ARIZONA
           DEPARTMENT OF CORRECTIONS,
              PETITIONER v. DANNY LEE
                      JONES
 ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF
            APPEALS FOR THE NINTH CIRCUIT
                             [May 30, 2024]

   JUSTICE JACKSON, dissenting.
   In its search for legal error in this capital habeas case,
the Court makes many mistakes of its own, including mis-
reading the Ninth Circuit’s opinion.* I write separately to
emphasize a particular misstep: the Court’s conclusion that
“the Ninth Circuit all but ignored the strong aggravating
circumstances in this case.” Ante, at 1. In my view, the
Ninth Circuit’s analysis satisfied its obligations under
Strickland v. Washington, 

 (1984).
   Per our longstanding test for evaluating an ineffective-
assistance-of-counsel claim in a capital case, a court “must
consider the totality of the evidence” and ask “whether
there is a reasonable probability that, absent the [trial
counsel’s] errors, the sentencer . . . would have concluded
that the balance of aggravating and mitigating circum-
stances did not warrant death.” 

. That is pre-
cisely what the Ninth Circuit did here. The panel not only
evaluated the mitigating evidence that Jones’s trial counsel
——————
  *Compare, e.g., ante, at 7–8 (accusing the panel of “appl[ying] a
strange Circuit rule that prohibits a court in a Strickland case from as-
sessing the relative strength of expert witness testimony”), with Jones v.
Ryan, 

, 1129 (CA9 2022) (“This is not to say, of course, that
a district court is prohibited from making credibility determinations”).
2                    THORNELL v. JONES

                     JACKSON, J., dissenting

failed to unearth, it also specifically considered all of the
aggravating factors. See Jones v. Ryan, 

,
1131 (CA9 2022). To assess prejudice, it then reasoned ex-
tensively—by analogy—considering precedent where both
the Circuit and this Court had granted habeas relief even
in the presence of similar aggravators. See 

 at 1131–
1133.
  To be sure, the Ninth Circuit’s discussion of the aggravat-
ing factors was concise. But there is no benchmark length
for any such discussion. Indeed, this Court has granted ha-
beas relief after similarly succinct evaluations of aggravat-
ing factors. See, e.g., Porter v. McCollum, 

, 41–
42 (2009) (per curiam) (discussing aggravators in one para-
graph); Rompilla v. Beard, 

, 390–393 (2005)
(no discussion of aggravators); Wiggins v. Smith, 

, 534–538 (2003) (same). We can hardly fault the Ninth
Circuit for using the same approach that this Court itself
has previously used.
  Thus, to me, the Court’s claim that the Ninth Circuit “all
but ignored” the aggravators, ante, at 1, rings hollow. And
the majority’s real critique does not appear to relate to the
Ninth Circuit’s methodology. Rather, it merely takes issue
with the weight that the Ninth Circuit assigned to each of
the relevant facts. I agree with JUSTICE SOTOMAYOR that
we are not the right tribunal to parse the extensive factual
record in this case in the first instance. That is doubly true
where the Ninth Circuit committed no legal error in review-
ing that record to begin with. I respectfully dissent.