(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., 200 U. S. 321, 337. 

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 firstdegree murders of Robert and Tisha Weaver and the attempted premeditated murder of Robert’s grandmother Katherine Gumina. Arizona 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 substantial to call for leniency.” Ariz. Rev. Stat. Ann. §13–703(E). The trial 

court found three aggravating circumstances that applied to both Robert’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 circumstance 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 mitigating 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 record” and “independently weighing all of the aggravating and mitigating evidence presented.” 185 Ariz. 471, 492, 917 P. 2d 200, 221. 

Jones later sought state postconviction review on the theory that defense 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 presented “ ‘barely. . . alter[ed] the sentencing profile presented to the sentencing judge.’ ” Jones v. Schriro, 450 F. Supp. 2d 1023, 1043 (quoting 

Strickland v. Washington, 466 U. S. 668, 700). The Ninth Circuit reversed, but this Court vacated that judgment and remanded for the

Ninth Circuit to determine whether, in light of Cullen v. Pinholster, 

563 U. S. 170, it had been proper to consider the new evidence presented at the federal evidentiary hearing. See Ryan v. Jones, 563 U. S. 

932. On reconsideration, the Ninth Circuit again granted habeas relief. The panel held that it was permissible to consider the new evidence 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, 52 F. 4th 1104, 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 mitigation evidence” as “enough to overcome . . . weight[y] . . . aggravating 

circumstances.” Id., at 1155. 

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 “prejudiced” him. Strickland, 466 U. S., at 687. 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 aggravating and mitigating circumstances did not warrant death.” Id., at 695. 

“A reasonable probability is a probability sufficient to undermine confidence in the outcome. That requires a substantial, not just conceivable, likelihood of a different result.” Pinholster, 563 U. S., at 189 (citation 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 aggravating. Strickland, 466 U. S., at 695. 

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 Circuit 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, 455 U. S. 104, 

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 
 

 

 

 

Cite as: 602 U. S. ____ (2024) 3 

Syllabus 

sentencer might deem relevant to the defendant’s moral culpability.” 

Brief for Respondent 14. This rule is squarely at odds with the established understanding of prejudice under Strickland, which requires a 

“reasonable probability” of a different result. Where aggravating factors greatly outweigh mitigating evidence, there may be no “reasonable probability” of a different result. Pp. 7–9.

(b) Turning to the issue of prejudice in this case, the mitigating evidence 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, 466 U. S., 

at 700. 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.” 185 Ariz., at 492, 917 

P. 2d, at 221. 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 cognitive impairment and did not find this evidence sufficient to warrant 

leniency. Ibid. 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 grandfather 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 selfreported and uncorroborated evidence “little . . . mitigating weight.” 

State v. Sharp, 193 Ariz. 414, 425, 973 P. 2d 1171, 1182. Pp. 12–13. 

(4) Finally, Jones produced evidence of substance abuse, but his 

history of substance abuse was “well-documented” at the time of sentencing, and the Arizona Supreme Court gave this fact “some mitigating weight,” 185 Ariz., at 491, 917 P. 2d, at 220. 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 circumstances—multiple homicides, cruelty, pecuniary motivation, and murder of a child—are given great weight in Arizona. The Arizona Supreme Court has repeatedly held that one or more of these aggravating 

circumstances outweighed mitigation evidence—even evidence that 

was “not insubstantial.” State v. Hampton, 213 Ariz. 167, 185, 140 

P. 3d 950, 968. 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 suggests that Jones has no reasonable probability of escaping the death 

penalty. Pp. 13–14. 

(d) Contrary to the Ninth Circuit’s conclusion, “the Strickland prejudice 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. 

52 F. 4th 1104, reversed and remanded. 

ALITO, J., delivered the opinion of the Court, in which ROBERTS, C. J., 

and THOMAS, GORSUCH, KAVANAUGH, and BARRETT, JJ., joined. SOTOMAYOR, J., filed a dissenting opinion, in which KAGAN, J., joined. JACKSON, J., filed a dissenting opinion. 
 

_________________ 

_________________ 

Cite as: 602 U. S. ____ (2024) 1 

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, 

pio@supremecourt.gov, 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 ordering the resentencing of a defendant who, in order to steal 

a gun collection, committed three gruesome killings, including 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 conclusion, the Ninth Circuit substantially departed from the 

well-established standard articulated by this Court in 

Strickland v. Washington, 466 U. S. 668 (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 collection. 

Once inside, Jones encountered Gumina, who was watching 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 create a wound several inches wide, extending from her left 

ear to her left cheek.” State v. Jones, 185 Ariz. 471, 489, 

917 P. 2d 200, 218 (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 

—————— 1Arizona charged Jones before Gumina’s death and elected not to 
 

Cite as: 602 U. S. ____ (2024) 3 

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 commission of the offense.” §13–703(F)(8). Second, he was motivated 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 circumstance: 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 “constan[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 essentially “part of the defense team.” 7 id., at 1831. Dr. Potts 

identified several “mitigating factors” that he thought warranted 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’ childhood,” 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 “contribut[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]” predisposed 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 responsibility” and that he had the “potential for rehabilitation.” 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 entire record” and “independently weighing all of the aggravating and mitigating evidence presented.” Jones, 185 

Ariz., at 492, 917 P. 2d, at 221. 

C 

Jones sought state postconviction review on the theory 

that defense counsel was ineffective. Jones argued that his 

attorney should have retained an independent neuropsychologist, 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.” 
 

Cite as: 602 U. S. ____ (2024) 5 

Opinion of the Court 

7 Record 1950. Jones also claimed that trial counsel failed 

to make a timely request for neurological or neuropsychological 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 28 U. S. C. §2254. The District Court held an 

evidentiary hearing but ultimately concluded that Jones 

could not show prejudice because the additional information he presented “‘barely . . . alter[ed] the sentencing

profile presented to the sentencing judge.’” Jones v. 

Schriro, 450 F. Supp. 2d 1023, 1043 (Ariz. 2006) (quoting 

Strickland, 466 U. S., at 700). The court reached this conclusion based on its assessment of “the credibility of the

parties’ witnesses,” including witnesses introduced by the

State to undercut Jones’s claims. 450 F. Supp. 2d, at 1038.

The Ninth Circuit reversed. See Jones v. Ryan, 583 F. 3d 

626 (2009). But this Court vacated that judgment and remanded for the Ninth Circuit to determine whether, in light

of Cullen v. Pinholster, 563 U. S. 170 (2011), it had been 

proper to consider the new evidence presented at the federal evidentiary hearing. See Ryan v. Jones, 563 U. S. 932 

(2011).

On reconsideration, the Ninth Circuit again granted habeas relief. The panel held that it was permissible to consider the new evidence 2 and concluded that there was a 

—————— 2The panel reasoned that the postconviction review court had not

reached the issue of prejudice, so it could review the issue de novo. Further, “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, 52 F. 4th 1104, 1123 (CA9 2022). Arizona 
 

 

6 THORNELL v. JONES 

Opinion of the Court 

“reasonable probability” that “Jones would not have received a death sentence” if that evidence had been presented at sentencing. Jones v. Ryan, 1 F. 4th 1179, 1196, 

1204 (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, 52 F. 4th 1104, 

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 review court on the Strickland prejudice inquiry. Judge Bennett, 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 “questionable, 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 defendants who have been convicted of the most horrific 

crimes.” Id., at 1137. 

We granted certiorari to review the Ninth Circuit’s interpretation and application of Strickland. 601 U. S. ___ 

(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. 
 

Cite as: 602 U. S. ____ (2024) 7 

Opinion of the Court 

II 

Jones claims that his Sixth Amendment right to the effective assistance of counsel was violated during the sentencing phase of his capital trial. To succeed on such a 

claim, a defendant must show that counsel provided a “deficient” performance that “prejudiced” him. Strickland, 466 

U. S., at 687. 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 balance of aggravating and mitigating circumstances did not 

warrant death.” Id., at 695. “A reasonable probability is a

probability sufficient to undermine confidence in the outcome. That requires a substantial, not just conceivable,

likelihood of a different result.” Pinholster, 563 U. S., at 

189 (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, 466 U. S., at 

697. 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 aggravating. 

Id., at 695. 

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 mention 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. Determining 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 opinion, it is hard to see how a court could decide how much 

weight to give the defense expert without making a comparative 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, 455 U. S. 104 (1982), but that is not 

so. Eddings held that a sentencer may not “refuse to consider . . . any relevant mitigating evidence.” Id., at 114. It 

did not hold that a sentencer cannot find mitigating evidence unpersuasive. See id., 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 reasonable 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 established understanding of prejudice, which requires a “reasonable probability” of a different result. Imagine a defendant with the worst possible aggravating circumstances, say, 
 

Cite as: 602 U. S. ____ (2024) 9 

Opinion of the Court 

multiple, vulnerable victims; torture; a lengthy record of violent 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 aggravating factors greatly outweigh the mitigating evidence, 

there may be no “reasonable probability” of a different result. 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 mitigating 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 aggravating 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 sentencing. 

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 resulted in a different sentence. 

Arizona courts had already received testimony that Jones

“suffers from a major mental illness,” likely a “form of Bipolar 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 alleged mental illness and his conduct on the night of the 

murders.” Jones, 185 Ariz., at 492, 917 P. 2d, at 221; accord, 

State v. Prince, 226 Ariz. 516, 542, 250 P. 3d 1145, 1171 

(2011) (discounting poor mental health when no “expert 

could establish [the defendant’s] mental state on the night 

of the shootings”); State v. Boggs, 218 Ariz. 325, 343, 185 

P. 3d 111, 129 (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 id., at 506–508; id., 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 between that disorder and violence. Id., at 459. Because none 

of Jones’s experts provided a real link between Jones’s disorders and the murders, their testimony would have done 

him little good in the Arizona courts. See State v. Poyson, 

250 Ariz. 48, 53, 58, 475 P. 3d 293, 298, 303 (2020) (failure

to link mitigating evidence to the crime may diminish its

weight); State v. Stuard, 176 Ariz. 589, 608, n. 12, 863 P. 2d 

881, 900, n. 12 (1993) (“[E]vidence of causation is required 

before mental impairment can be considered a significant 

mitigating factor”). 
 

 

Cite as: 602 U. S. ____ (2024) 11 

Opinion of the Court 

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. 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 biological 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 result 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 contributed 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, 185 Ariz., at 492, 917 P. 2d, at 221 (crediting 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 corroborate any of these injuries.” Jones, 450 F. Supp. 2d, at 

1039, 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 “corroborate[s]” testimony the Arizona courts already credited. 

Jones, 185 Ariz., at 492, 917 P. 2d, at 221. Introducing it 

“would have offered an insignificant benefit, if any at all.” 

Wong v. Belmontes, 558 U. S. 15, 23 (2009) (per curiam). 
 

 

 

12 THORNELL v. JONES 

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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 unconnected 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 alcohol 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 proceedings. 2 id., at 503–504. And his mother and second stepfather 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.” Record 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, 193 Ariz. 414, 425, 973 P. 2d 1171, 1182 

(1999); accord, State v. Gerlaugh, 144 Ariz. 449, 462, 698 

P. 2d 694, 707 (1985).

Jones’s physical-abuse allegation against Randy is not

much more helpful. Granted, his sister seconded his allegation. 4 Record 982–987. But other record evidence contradicts it. For instance, Jones told Dr. Potts that Randy 
 

Cite as: 602 U. S. ____ (2024) 13 

Opinion of the Court 

was “quite stern and a disciplinarian yet certainly not physically abusive.” Id., 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, 185 Ariz. 192, 194, 914 P. 2d 225, 227 (1996); see 

also Gerlaugh, 144 Ariz., at 462, 698 P. 2d, at 707; State v. 

Carriger, 143 Ariz. 142, 153, 692 P. 2d 991, 1002 (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 Respondent 44. But Jones’s history of substantive abuse was

“well-documented” at the time of sentencing. Jones, 185 

Ariz., at 491, 917 P. 2d, at 220. 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 (presentencing report noting that Jones began consuming alcohol and 

using drugs at 13). And that court gave this fact “some mitigating weight.” Jones, 185 Ariz., at 491, 917 P. 2d, at 220. 

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 circumstances. These circumstances—multiple homicides, cruelty, pecuniary motivation, and murder of a child—are 

given great weight in Arizona. See State v. Garza, 216 Ariz. 

56, 72, 163 P. 3d 1006, 1022 (2007) (multiple-homicides aggravator gets “‘extraordinary weight’”); Poyson, 250 Ariz., 

at 57, 475 P. 3d, at 302 (the cruelty and pecuniary-motivation aggravators are “particularly weighty”); State v. Newell, 212 Ariz. 389, 406, 132 P. 3d 833, 850 (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, 213 Ariz. 167, 185, 

140 P. 3d 950, 968 (2006) (concluding that the multiplehomicides aggravator outweighed evidence of a “horrendous childhood”); see also Poyson, 250 Ariz., at 57–58, 475 

P. 3d, at 302–303 (listing several cases in which the multiple-homicides aggravator alone outweighed all mitigating

circumstances); State v. McKinney, 245 Ariz. 225, 227, 426 

P. 3d 1204, 1206 (2018) (cruelty and pecuniary-motivation

aggravators outweighed evidence that a defendant had “endured a horrific childhood” and suffered from mental illness). 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 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: 602 U. S. ____ (2024) 15 

Opinion of the Court 

In these cases, the Ninth Circuit stated, we found prejudice 

when counsel failed to present “classic mitigating evidence,” even though the defendants had committed “brutal 

crimes.” Id., at 1133. 

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 defense counsel introduced little, if any, mitigating evidence

at the original sentencing. See Porter v. McCollum, 558 

U. S. 30, 41 (2009) (per curiam); Williams v. Taylor, 529 

U. S. 362, 395–398 (2000); Rompilla v. Beard, 545 U. S. 374, 

378, 393 (2005); Wiggins v. Smith, 539 U. S. 510, 515, 534– 

535 (2003). Jones, by contrast, started with much more mitigation. And in most of the other cases, the sentencer found 

only a few aggravating circumstances. See Porter, 558 

U. S., at 42 (three aggravators, two of which the sentencing 

judge thought “were insufficient to warrant death”); Williams, 529 U. S., at 370, 398 (one aggravator); Wiggins, 539 

U. S., at 537 (one aggravator). That is a far cry from the

weighty aggravating circumstances present here. Poyson, 

250 Ariz., at 57, 475 P. 3d, at 302. 

* * * 

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 reasonably likely that the additional evidence would have 

avoided a death sentence. This analysis requires an evaluation 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 downplayed 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: 602 U. S. ____ (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 ignored 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, 558 U. S. 15, 26 (2009) (per curiam), and must

“reweigh the evidence in aggravation against the totality of 

available mitigating evidence,” Wiggins v. Smith, 539 U. S. 

510, 534 (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 settle [a] fact-sensitive issue.” CRST Van Expedited, Inc. v. 

EEOC, 578 U. S. 419, 435 (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, 544 U. S. 709, 718, n. 7 

(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 instance, I respectfully dissent. 
_________________ 

_________________ 

Cite as: 602 U. S. ____ (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 misreading 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, 466 U. S. 668 (1984).

Per our longstanding test for evaluating an ineffectiveassistance-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 circumstances did not warrant death.” Id., at 695. That is precisely 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 assessing the relative strength of expert witness testimony”), with Jones v. 

Ryan, 52 F. 4th 1104, 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, 52 F. 4th 1104, 

1131 (CA9 2022). To assess prejudice, it then reasoned extensively—by analogy—considering precedent where both 

the Circuit and this Court had granted habeas relief even

in the presence of similar aggravators. See id., at 1131– 

1133. 

To be sure, the Ninth Circuit’s discussion of the aggravating factors was concise. But there is no benchmark length 

for any such discussion. Indeed, this Court has granted habeas relief after similarly succinct evaluations of aggravating factors. See, e.g., Porter v. McCollum, 558 U. S. 30, 41– 

42 (2009) (per curiam) (discussing aggravators in one paragraph); Rompilla v. Beard, 545 U. S. 374, 390–393 (2005) 

(no discussion of aggravators); Wiggins v. Smith, 539 U. S. 

510, 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 reviewing that record to begin with. I respectfully dissent.