(Slip Opinion)              OCTOBER TERM, 2017                                       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

 AYESTAS, AKA ZELAYA COREA v. DAVIS, DIRECTOR, 

   TEXAS DEPARTMENT OF CRIMINAL JUSTICE, 

    CORRECTIONAL INSTITUTIONS DIVISION


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

   No. 16–6795. Argued October 30, 2017—Decided March 21, 2018
Petitioner Ayestas was convicted of murder and sentenced to death in a
  Texas state court. He secured new counsel, but his conviction and
  sentence were affirmed on appeal. A third legal team sought, unsuc-
  cessfully, state habeas relief, claiming trial-level ineffective assis-
  tance of counsel but not counsel’s failure to investigate petitioner’s
  mental health and alcohol and drug abuse during the trial’s penalty
  phase. His fourth set of attorneys did raise that failure in a federal
  habeas petition, but because the claim had never been raised in state
  court, the District Court held, it was barred by procedural default.
  That decision was vacated and remanded for reconsideration in light
  of Martinez v. Ryan, 566 U. S. 1—where this Court held that an Ari-
  zona prisoner seeking federal habeas relief could overcome the proce-
  dural default of a trial-level ineffective-assistance-of-counsel claim by
  showing that the claim is substantial and that state habeas counsel
  was also ineffective in failing to raise the claim in a state habeas pro-
  ceeding—and Trevino v. Thaler, 569 U. S. 413—which extended that
  holding to Texas prisoners. Petitioner filed an ex parte motion asking
  the District Court for funding to develop his claim that both his trial
  and state habeas counsel were ineffective, relying on 18 U. S. C.
  §3599(f), which provides, in relevant part, that a district court “may
  authorize” funding for “investigative, expert, or other services . . .
  reasonably necessary for the representation of the defendant.” The
  court found his claim precluded by procedural default and thus de-
  nied his funding request. The Fifth Circuit also rejected the funding
  claim under its precedent: that a §3599(f) funding applicant must
  show that he has a “substantial need” for investigative or other ser-
2                         AYESTAS v. DAVIS

                                Syllabus

 vices, and that funding may be denied when an applicant fails to pre-
 sent “a viable constitutional claim that is not procedurally barred.”
 817 F. 3d 888, 895–896.
Held:
    1. The District Court’s denial of petitioner’s funding request was a
 judicial decision subject to appellate review under the standard juris-
 dictional provisions. Pp. 7–14.
       (a) Title 28 U. S. C. §§1291, 2253, and 1254 confer jurisdiction to
 review decisions made by a district court in a judicial capacity. “Ad-
 ministrative” decisions—about, e.g., facilities, personnel, equipment,
 supplies, and rules of procedure—are “not subject to [this Court’s] re-
 view,” Hohn v. United States, 524 U. S. 236, 245, but the District
 Court’s ruling here does not remotely resemble such decisions. Peti-
 tioner’s request was made by motion in his federal habeas proceed-
 ing, which is indisputably a judicial proceeding. And resolution of
 the funding question requires the application of a legal standard—
 whether the funding is “reasonably necessary” for effective represen-
 tation—that demands an evaluation of petitioner’s prospects of ob-
 taining habeas relief. Pp. 8–10.
       (b) Respondent’s arguments in support of her claim that §3599’s
 funding requests are nonadversarial and administrative are unper-
 suasive. First, that the requests can be decided ex parte does not
 make the proceeding nonadversarial. The habeas proceeding here
 was clearly adversarial. And petitioner and respondent plainly have
 adverse interests on the funding question and have therefore squared
 off as adversaries. The mere fact that a §3599 funding request may
 sometimes be made ex parte is thus hardly dispositive. Second, noth-
 ing in §3599 even hints that the funding decisions may be revised by
 the Director of the Administrative Office of the Courts. Lower court
 cases that appear to have accepted Administrative Office review of
 certain Criminal Justice Act (CJA) payments, even if a proper inter-
 pretation of the CJA, are inapposite.           Finally, the fact that
 §3599(g)(2) requires funding in excess of the generally applicable
 statutory cap to be approved by the circuit’s chief judge or another
 designated circuit judge, instead of by a panel of three, does not make
 the proceeding administrative. If Congress wishes to make certain
 rulings reviewable by a single circuit judge, the Constitution does not
 stand in the way. Pp. 10–14.
    2. The Fifth Circuit did not apply the correct legal standard in af-
 firming the denial of petitioner’s funding request. Section 3599 au-
 thorizes funding for the “reasonably necessary” services of experts,
 investigators, and the like. But the Fifth Circuit’s requirement that
 applicants show a “substantial need” for the services is arguably a
 more demanding standard. Section 3599 appears to use the term
                     Cite as: 584 U. S. ____ (2018)                     3

                                Syllabus

  “necessary” to mean something less than essential. Because it makes
  little sense to refer to something as being “reasonably essential,” the
  Court concludes that the statutory phrase calls for the district court
  to determine, in its discretion, whether a reasonable attorney would
  regard the services as sufficiently important, guided by considera-
  tions detailed in the opinion. The term “substantial” in the Fifth Cir-
  cuit’s test, however, suggests a heavier burden. And that court exac-
  erbated the difference by also requiring a funding applicant to
  present “a viable constitutional claim that is not procedurally
  barred.” That rule that is too restrictive after Trevino, see 569 U. S.
  at 429, because, in cases where funding stands a credible chance of
  enabling a habeas petitioner to overcome the procedural default ob-
  stacle, it may be error for a district court to refuse funding. That be-
  ing said, district courts were given broad discretion in assessing fund-
  ing requests when Congress changed the phrase “shall authorize” in
  §3599’s predecessor statute, see 21 U. S. C. §848(q)(9), to “may au-
  thorize” in §3599(f). A funding applicant must not be expected to
  prove that he will be able to win relief if given the services, but the
  “reasonably necessary” test does require an assessment of the likely
  utility of the services requested.
     Respondent’s alternative ground for affirmance—that funding is
  never “reasonably necessary” where a habeas petitioner seeks to pre-
  sent a procedurally defaulted ineffective-assistance-of-trial-counsel
  claim that depends on facts outside the state-court record—remains
  open for the Fifth Circuit to consider on remand. Pp. 14–19.
817 F. 3d 888, vacated and remanded.

   ALITO, J., delivered the opinion for a unanimous Court. SOTOMAYOR,
J., filed a concurring opinion, in which GINSBURG, J., joined.
                       Cite as: 584 U. S. ____ (2018)                              1

                            Opinion of the Court

    NOTICE: This opinion is subject to formal revision before publication in the
    preliminary print of the United States Reports. Readers are requested to
    notify the Reporter of Decisions, Supreme Court of the United States, Wash-
    ington, D. C. 20543, of any typographical or other formal errors, in order
    that corrections may be made before the preliminary print goes to press.


SUPREME COURT OF THE UNITED STATES
                                  _________________

                                  No. 16–6795
                                  _________________


 CARLOS MANUEL AYESTAS, AKA DENNIS ZELAYA

 COREA, PETITIONER v. LORIE DAVIS, DIRECTOR, 

  TEXAS DEPARTMENT OF CRIMINAL JUSTICE, 

    CORRECTIONAL INSTITUTIONS DIVISION

 ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF 

            APPEALS FOR THE FIFTH CIRCUIT

                               [March 21, 2018]


  JUSTICE ALITO delivered the opinion of the Court.
  Petitioner Carlos Ayestas, who was convicted of murder
and sentenced to death in a Texas court, argues that he
was wrongfully denied funding for investigative services
needed to prove his entitlement to federal habeas relief.
Petitioner moved for funding under 18 U. S. C. §3599(f ),
which makes funds available if they are “reasonably nec-
essary,” but petitioner’s motion was denied. We hold that
the lower courts applied the wrong legal standard, and we
therefore vacate the judgment below and remand for
further proceedings.
                              I

                              A

  In 1997, petitioner was convicted of capital murder in a
Texas court. Evidence at trial showed that he and two
accomplices invaded the home of a 67-year-old Houston
woman, Santiaga Paneque, bound her with duct tape and
electrical cord, beat and strangled her, and then made off
with a stash of her belongings.
2                    AYESTAS v. DAVIS

                     Opinion of the Court

   The jury also heard testimony from Henry Nuila regard-
ing an incident that occurred about two weeks after the
murder. Petitioner was drunk at the time, and he re-
vealed to Nuila that he had recently murdered a woman in
Houston. Petitioner then brandished an Uzi machinegun
and threatened to murder Nuila if he did not help peti-
tioner kill his two accomplices. Fortunately for Nuila,
petitioner kept talking until he eventually passed out;
Nuila then called the police, who arrested petitioner, still
in possession of the gun.
   After the jury found petitioner guilty, it was asked to
determine whether he should be sentenced to death or to
life in prison. In order to impose a death sentence, Texas
law required the jury to answer the following three ques-
tions. First, would petitioner pose a continuing threat to
society? Second, had he personally caused the death of the
victim, intended to kill her, or anticipated that she would
be killed? Third, in light of all the evidence surrounding
the crime and petitioner’s background, were there suffi-
cient mitigating circumstances to warrant a sentence of
life without parole instead of death? Tex. Code Crim.
Proc. Ann., Art. 37.071, §§2(b), (e) (Vernon Cum. Supp.
2017). Only if the jury gave a unanimous yes to the first
two questions, and a unanimous no to the third question,
could a death sentence be imposed; otherwise, petitioner
would receive a sentence of life without parole. See
§§2(d)(2), (f )(2), (g).
   In asking the jury to impose a death sentence, the pros-
ecution supplemented the trial record with evidence of
petitioner’s criminal record and his encounter with a man
named Candelario Martinez a few days after the murder.
Martinez told the jury that he was standing in a hotel
parking lot waiting for a friend when petitioner ap-
proached and began to make small talk. Before long,
petitioner pulled out a machinegun and forced Martinez
into a room where two of petitioner’s compatriots were
                  Cite as: 584 U. S. ____ (2018)            3

                      Opinion of the Court

holding Martinez’s friend at knifepoint. Ordered to lie
down on the bathroom floor and await his execution,
Martinez begged for his life while petitioner and his co-
horts haggled about who would carry out the killing.
Finally, petitioner relented, but he threatened to kill
Martinez and his family if he contacted the police. Peti-
tioner then stole Martinez’s truck.
   Petitioner’s trial counsel presented very little mitigation
evidence. This was due, at least in part, to petitioner’s
steadfast refusal for many months to allow his lawyers to
contact his family members, who were living in Honduras
and might have testified about his character and upbring-
ing. Petitioner gave in on the eve of trial, and at that
point, according to the state habeas courts, his lawyers
“made every effort to contact [his] family.” App. 171.
They repeatedly contacted petitioner’s family members
and urged them to attend the trial; they requested that
the U. S. Embassy in Honduras facilitate family members’
travel to the United States; and they met in person with
the Honduran Consulate to seek assistance. But these
efforts were to no avail. Petitioner’s sister told his legal
team that the family would not leave Honduras because
the journey would create economic hardship and because
their father was ill and had killed one of their neighbors.
A defense attorney who spoke to petitioner’s mother testi-
fied that she seemed unconcerned about her son’s situa-
tion. In general, the state habeas courts found, petitioner
“did nothing to assist counsel’s efforts to contact his family
and did not want them contacted by the consulate or
counsel.” Id., at 174.
   In the end, the only mitigation evidence introduced by
petitioner’s trial counsel consisted of three letters from
petitioner’s English instructor. The letters, each two
sentences long, described petitioner as “a serious and
attentive student who is progressing well in English.”
Ibid.
4                    AYESTAS v. DAVIS

                     Opinion of the Court

  The jury unanimously concluded that petitioner should
be sentenced to death, and a capital sentence was im-
posed. Petitioner secured new counsel to handle his ap-
peal, and his conviction and sentence were affirmed by the
Texas Court of Criminal Appeals in 1998. Ayestas v.
State, No. 72,928, App. 115. Petitioner did not seek review
at that time from this Court.
                              B
   While petitioner’s direct appeal was still pending, a
third legal team filed a habeas petition on his behalf in
state court. This petition included several claims of trial-
level ineffective assistance of counsel, but the petition did
not assert that trial counsel were ineffective for failing to
investigate petitioner’s mental health and abuse of alcohol
and drugs. Petitioner’s quest for state habeas relief ended
unsuccessfully in 2008. Ex parte Ayestas, No. WR–69,674–
01 (Tex. Ct. Crim. App., Sept. 10, 2008), 2008 WL 4151814
(per curiam) (unpublished).
   In 2009, represented by a fourth set of attorneys, peti-
tioner filed a federal habeas petition under 28 U. S. C.
§2254, and this time he did allege that his right to the
effective assistance of counsel at trial was violated because
his attorneys failed to conduct an adequate search for
mitigation evidence. As relevant here, petitioner argued
that trial counsel overlooked evidence that he was mentally
ill and had a history of drug and alcohol abuse. Ayestas
v. Thaler, Civ. Action No. H–09–2999 (SD Tex., Jan. 26,
2011), 2011 WL 285138, *4. Petitioner alleged that he had
a history of substance abuse, and he noted that he had
been diagnosed with schizophrenia while the state habeas
proceeding was still pending. See Pet. for Writ of Habeas
Corpus in Ayestas v. Quarterman, No. 4:09–cv–2999 (SD
Tex.), Doc. 1, pp. 21–23. Petitioner claimed that trial
counsel’s deficient performance caused prejudice because
there was a reasonable chance that an adequate investiga-
                 Cite as: 584 U. S. ____ (2018)            5

                     Opinion of the Court

tion would have produced mitigation evidence that would
have persuaded the jury to spare his life.
   Among the obstacles standing between petitioner and
federal habeas relief, however, was the fact that he never
raised this trial-level ineffective-assistance-of-counsel
claim in state court. The District Court therefore held
that the claim was barred by procedural default, Ayestas v.
Thaler, 2011 WL 285138, *4–*7, and the Fifth Circuit
affirmed, Ayestas v. Thaler, 462 Fed. Appx. 474, 482
(2012) (per curiam).
   Petitioner sought review in this Court, and we vacated
the decision below and remanded for reconsideration in
light of two of our subsequent decisions, Martinez v. Ryan,
566 U. S. 1 (2012), and Trevino v. Thaler, 569 U. S. 413
(2013). Ayestas v. Thaler, 569 U. S. 1015 (2013). Martinez
held that an Arizona prisoner seeking federal habeas relief
could overcome the procedural default of a trial-level
ineffective-assistance-of-counsel claim by showing that the
claim is substantial and that state habeas counsel was
also ineffective in failing to raise the claim in a state
habeas proceeding. 566 U. S., at 14. Trevino extended
that holding to Texas prisoners, 569 U. S., at 416–417, and
on remand, petitioner argued that he fell within Trevino
because effective state habeas counsel would have uncov-
ered evidence showing that trial counsels’ investigative
efforts were deficient.
   To assist in developing these claims, petitioner filed an
ex parte motion asking the District Court for $20,016 in
funding to conduct a search for evidence supporting his
petition. He relied on 18 U. S. C. §3599(f ), which provides
in relevant part as follows:
       “Upon a finding that investigative, expert, or other
    services are reasonably necessary for the representa-
    tion of the defendant, whether in connection with is-
    sues relating to guilt or the sentence, the court may
6                    AYESTAS v. DAVIS

                     Opinion of the Court

    authorize the defendant’s attorneys to obtain such
    services on behalf of the defendant and, if so author-
    ized, shall order the payment of fees and expenses
    therefor.”
Petitioner averred that the funds would be used to conduct
an investigation that would show that his trial counsel
and his state habeas counsel were ineffective. Accordingly,
he claimed, the investigation would establish both that
his trial-level ineffective-assistance-of-counsel claim was
not barred by procedural default and that he was entitled
to resentencing based on the denial of his Sixth Amend-
ment right to the effective assistance of trial counsel.
   The District Court refused the funding request and
ultimately denied petitioner’s habeas petition. Ayestas v.
Stephens, Civ. Action No. H–09–2999, (SD Tex., Nov. 18,
2014), 2014 WL 6606498, *6–*7. On the merits of peti-
tioner’s new ineffective-assistance-of-trial-counsel claim,
the District Court held that petitioner failed both prongs
of the Strickland test. See Strickland v. Washington, 466
U. S. 668 (1984). Noting that most of the evidence bearing
on petitioner’s mental health had emerged only after he
was sentenced, the court concluded that petitioner’s trial
lawyers were not deficient in failing to find such evidence
in time for the sentencing proceeding. 2014 WL 6606498,
*5. In addition, the court found that state habeas counsel
did not render deficient performance by failing to investi-
gate petitioner’s history of substance abuse, and that, in
any event, petitioner was not prejudiced at the sentencing
phase of the trial or during the state habeas proceedings
because the potential mitigation evidence at issue would
not have made a difference to the jury in light of “the
extremely brutal nature of [the] crime and [petitioner’s]
history of criminal violence.” Ibid.
   With respect to funding, the District Court pointed to
Fifth Circuit case law holding that a §3599(f ) funding
                     Cite as: 584 U. S. ____ (2018)                  7

                         Opinion of the Court

applicant cannot show that investigative services are
“ ‘reasonably necessary’ ” unless the applicant can show
that he has a “ ‘substantial need’ ” for those services. Id.,
at *6. In addition, the court noted that “[t]he Fifth Circuit
upholds the denial of funding” when, among other things,
“a petitioner has . . . failed to supplement his funding
request with a viable constitutional claim that is not
procedurally barred.” Ibid. (internal quotation marks
omitted).
    Given its holding that petitioner’s new ineffective-
assistance-of-counsel claim was precluded by procedural
default, this rule also doomed his request for funding. The
District Court denied petitioner’s habeas petition and
refused to grant him a certificate of appealability (COA).
Id., at *7. On appeal, the Fifth Circuit held that a COA
was not needed for review of the funding issue, but it
rejected that claim for essentially the same reasons as the
District Court, citing both the “substantial need” test and
the rule that funding may be denied when a funding appli-
cant fails to present “a viable constitutional claim that is
not procedurally barred.” Ayestas v. Stephens, 817 F. 3d
888, 895–896 (2016) (internal quotation marks omitted).
With respect to petitioner’s other claims, including his
claim of ineffective assistance of trial counsel, the Fifth
Circuit refused to issue a COA. Id., at 898.
                             C
  We granted certiorari to decide whether the lower courts
applied the correct legal standard in denying the funding
request. 581 U. S. ___ (2017).
                            II
  Before we reach that question, however, we must con-
sider a jurisdictional argument advanced by respondent,
the Director of the Texas Department of Criminal Justice.1
——————
 1 We   also consider a jurisdictional issue not raised by the parties,
8                        AYESTAS v. DAVIS

                         Opinion of the Court

Respondent contends that the District Court’s denial of
petitioner’s funding request was an administrative, not a
judicial, decision and therefore falls outside the scope of
the jurisdictional provisions on which petitioner relied in
seeking review in the Court of Appeals and in this Court.
                           A
  When the District Court denied petitioner’s funding
request and his habeas petition, he took an appeal to the
——————
namely, whether we have jurisdiction even though no COA has yet
been issued. We do not have jurisdiction if jurisdiction was lacking in
the Court of Appeals, and the jurisdiction of a court of appeals to
entertain an appeal from a final order in a habeas proceeding is de-
pendent on the issuance of a COA. See 28 U. S. C. §2253(c)(l); Gonzalez
v. Thaler, 565 U. S. 134, 142 (2012).
   In this case, petitioner appealed an order of the District Court that
denied both his request for funding under 18 U. S. C. §3599 and his
underlying habeas claims. The Court of Appeals denied a COA as to
the merits of his request for habeas relief but held that a COA was not
required insofar as petitioner challenged the District Court’s denial of
funding under §3599. The Fifth Circuit relied on Harbison v. Bell, 556
U. S. 180 (2009), in which a prisoner appealed from an order that
denied counsel under §3599 for a state clemency proceeding but that
did not address the merits of any habeas petition. This Court held that
a COA was not required. Here, petitioner took his appeal from the final
order in his habeas proceeding.
   The parties have not briefed whether that difference between Harbi-
son and the present case is relevant or whether an appeal from a denial
of a §3599 request for funding would fit within the COA framework,
and we find it unnecessary to resolve the issue. Though we take no
view on the merits, we will assume for the sake of argument that the
Court of Appeals could not entertain petitioner’s §3599 claim without
the issuance of a COA.
   We may review the denial of a COA by the lower courts. See, e.g.,
Miller-El v. Cockrell, 537 U. S. 322, 326–327 (2003). When the lower
courts deny a COA and we conclude that their reason for doing so was
flawed, we may reverse and remand so that the correct legal standard
may be applied. See Slack v. McDaniel, 529 U. S. 473, 485–486, 489–
490 (2000). We take that course here. As we will explain, the correct-
ness of the rule applied by the District Court in denying the funding
request was not only debatable; it was erroneous.
                      Cite as: 584 U. S. ____ (2018)                       9

                           Opinion of the Court

Fifth Circuit under 28 U. S. C. §§1291 and 2253, which
grant the courts of appeals jurisdiction to review final
“decisions” and “orders” of a district court.2 And when the
Fifth Circuit affirmed, petitioner sought review in this
Court under §1254, which gives us jurisdiction to review
“[c]ases” in the courts of appeals.3 As respondent correctly
notes, these provisions confer jurisdiction to review deci-
sions made by a district court in a judicial capacity. But
we have recognized that not all decisions made by a fed-
eral court are “judicial” in nature; some decisions are prop-
erly understood to be “administrative,” and in that case they
are “not subject to our review.” Hohn v. United States, 524
U. S. 236, 245 (1998).
   The need for federal judges to make many administra-
tive decisions is obvious. The Federal Judiciary, while
tiny in comparison to the Executive Branch, is neverthe-
less a large and complex institution, with an annual budget
exceeding $7 billion and more than 32,000 employees.
See Administrative Office of the U. S. Courts, The Judici-
ary FY 2018 Congressional Budget Summary Revised 9–
10 (June 2017). Administering this operation requires
many “decisions” in the ordinary sense of the term—
decisions about such things as facilities, personnel,
——————
  2 In relevant part §1291 declares that “[t]he courts of appeals . . . shall
have jurisdiction of appeals from all final decisions of the district courts
of the United States, the United States District Court for the District of
the Canal Zone, the District Court of Guam, and the District Court of
the Virgin Islands, except where a direct review may be had in the
Supreme Court.”
   Similarly, §2253 provides, as relevant, that “[i]n a habeas corpus
proceeding or a proceeding under section 2255 before a district judge,
the final order shall be subject to review, on appeal, by the court of
appeals for the circuit in which the proceeding is held.” §2253(a).
   3 “Cases in the courts of appeals may be reviewed by the Supreme

Court by . . . writ of certiorari granted upon the petition of any party to
any civil or criminal case, before or after rendition of judgment or
decree.” §1254(1).
10                   AYESTAS v. DAVIS

                     Opinion of the Court

equipment, supplies, and rules of procedure. In re Appli-
cation for Exemption from Electronic Pub. Access Fees by
Jennifer Gollan and Shane Shifflett, 728 F. 3d 1033, 1037
(CA9 2013). It would be absurd to suggest that every
“final decision” on any such matter is appealable under
§1291 or reviewable in this Court under §1254. See Hohn,
supra; 15A C. Wright, A. Miller, & E. Cooper, Federal
Practice and Procedure §3903, pp. 134–135 (2d ed. 1992).
Such administrative decisions are not the kind of decisions
or orders—i.e., decisions or orders made in a judicial ca-
pacity—to which the relevant jurisdictional provisions
apply.
   Respondent argues that the denial of petitioner’s fund-
ing request was just such an administrative decision, but
the District Court’s ruling does not remotely resemble the
sort of administrative decisions noted above. Petitioner’s
request was made by motion in his federal habeas proceed-
ing, which is indisputably a judicial proceeding. And as
we will explain, resolution of the funding question re-
quires the application of a legal standard—whether the
funding is “reasonably necessary” for effective representa-
tion—that demands an evaluation of petitioner’s prospects
of obtaining habeas relief. We have never held that a
ruling like that is administrative and thus not subject to
appellate review under the standard jurisdictional provi-
sions.
   Respondent claims that two factors support the conclu-
sion that the funding decision was administrative, but her
argument is unpersuasive.
                             B
  Respondent first argues as follows: Judicial proceedings
must be adversarial; 18 U. S. C. §3599(f ) funding adjudi-
cations are not adversarial because the statute allows
requests to be decided ex parte; therefore, §3599(f ) funding
adjudications are not judicial in nature. This reasoning is
                 Cite as: 584 U. S. ____ (2018)           11

                     Opinion of the Court

flawed.
   It is certainly true that cases and controversies in our
legal system are adversarial in nature, e.g., Bond v. United
States, 564 U. S. 211, 217 (2011); Aetna Life Ins. Co. v.
Haworth, 300 U. S. 227, 240–241 (1937), but here, both
the habeas proceeding as a whole and the adjudication of
the specific issue of funding were adversarial. That the
habeas proceeding was adversarial is beyond dispute. And
on the funding question, petitioner and respondent plainly
have adverse interests and have therefore squared off as
adversaries. The motion for funding was formally noted
as “opposed” on the Disrict Court’s docket. App. 341. That
is not surprising: On one side, petitioner is seeking fund-
ing that he hopes will prevent his execution. On the other,
respondent wants to enforce the judgment of the Texas
courts and to do so without undue delay. Petitioner and
respondent have vigorously litigated the funding question
all the way to this Court.
   In arguing that the funding dispute is nonadversarial,
respondent attaches too much importance to the fact that
the request was made ex parte. As we have noted, the
“ex parte nature of a proceeding has not been thought to
imply that an act otherwise within a judge’s lawful juris-
diction was deprived of its judicial character.” Forrester v.
White, 484 U. S. 219, 227 (1988).
   In our adversary system, ex parte motions are disfa-
vored, but they have their place. See, e.g., Hohn, supra, at
248 (application for COA); Dalia v. United States, 441
U. S. 238, 255 (1979) (application for a search warrant); 50
U. S. C. §1805(a) (application to conduct electronic surveil-
lance for foreign intelligence); 18 U. S. C. §2518(3) (appli-
cations to intercept “wire, oral, or electronic communica-
tions”); 15 U. S. C. §1116(d)(1)(A) (application to seize
certain goods and counterfeit marks involved in violations
of the trademark laws); Fed. Rule Crim. Proc. 17(b) (appli-
cation for witness subpoena); Fed. Rule Crim. Proc. 47(c)
12                    AYESTAS v. DAVIS

                      Opinion of the Court

(generally recognizing ex parte motions and applications);
Ullmann v. United States, 350 U. S. 422, 423–424, 434
(1956) (application for an order granting a witness immun-
ity in exchange for self-incriminating testimony); United
States v. Monsanto, 491 U. S. 600, 603–604 (1989) (motion
to freeze defendant’s assets pending trial).
   Thus, the mere fact that a §3599 funding request may
sometimes be made ex parte is hardly dispositive. See
Hohn, 524 U. S., at 249; Tutun v. United States, 270 U. S.
568, 577 (1926).
                               C
  Respondent’s second argument is based on the vener-
able principle “that Congress cannot vest review of the
decisions of Article III courts in” entities other than “supe-
rior courts in the Article III hierarchy.” Plaut v. Spend-
thrift Farm, Inc., 514 U. S. 211, 218–219 (1995) (citing
Hayburn’s Case, 2 Dall. 409 (1792)). Respondent claims
that §3599 funding decisions may be revised by the Direc-
tor of the Administrative Office of the Courts and that this
shows that such decisions must be administrative. This
argument, however, rests on a faulty premise. Nothing in
§3599 even hints that review by the Director of the Ad-
ministrative Office is allowed.
  Respondent’s argument rests in part on a handful of old
lower court cases that appear to have accepted Adminis-
trative Office review of Criminal Justice Act of 1964 (CJA)
payments that had been authorized by a District Court
and approved by the chief judge of the relevant Circuit.
See United States v. Aadal, 282 F. Supp. 664, 665 (SDNY
1968); United States v. Gast, 297 F. Supp. 620, 621–622
(Del. 1969); see also United States v. Hunter, 385 F. Supp.
358, 362 (DC 1974). The basis for these decisions was a
provision of the CJA, 18 U. S. C. §3006A(h) (1964 ed.),
stating that CJA payments “shall be made under the
supervision of the Director of the Administrative Office of
                     Cite as: 584 U. S. ____ (2018)                   13

                          Opinion of the Court

the United States Courts.”4
   It is not clear whether these decisions correctly inter-
preted the CJA,5 but in any event, no similar language
appears in §3599. And respondent has not identified a
single instance in which the Director of the Administrative
Office or any other nonjudicial officer has attempted to
review or alter a §3599 decision.
   Moreover, attorneys’ requests for CJA funds are mark-
edly different from the funding application at issue here.
Attorneys appointed under the CJA typically submit those
requests after the conclusion of the case, and the prosecu-
tion has no stake in the resolution of the matter. The
judgment in the criminal case cannot be affected by a
decision on compensation for services that have been
completed, and any funds awarded come out of the budget
of the Judiciary, not the Executive. See 18 U. S. C.
§3006A(i) (2012 ed.). Thus, the adversaries in the crimi-
nal case are not pitted against each other. In this case,
on the other hand, as we have explained, petitioner
and respondent have strong adverse interests.             For
these reasons, we reject respondent’s argument that the
adjudication of the funding issue is nonadversarial and
administrative.
   Respondent, however, claims that the funding decision
is administrative for an additional reason. “A §3599(f )
funding determination is properly deemed administra-
tive,” she contends, “because it . . . may be revised outside
the traditional Article III judicial hierarchy.” Brief for
Respondent 23. The basis for this argument is a provision
of §3599 stating that funding in excess of the generally
——————
  4 This language now appears at 18 U. S. C. §3006A(i) (2012 ed.).
  5 As far as we are aware, neither the Administrative Office nor any
other nonjudicial entity currently claims the power to revise or reject a
CJA compensation order issued by a court. Nothing in the CJA Guide-
lines suggests such a policy. See generally 7A Guide to Judiciary Policy
(May 17, 2017).
14                    AYESTAS v. DAVIS

                      Opinion of the Court

applicable statutory cap of $7,500 must be approved by the
chief judge of the circuit or another designated circuit
judge. §3599(g)(2). If a funding decision is judicial and
not administrative, respondent suggests, it could not be
reviewed by a single circuit judge as opposed to a panel of
three.
  This argument confuses what is familiar with what is
constitutionally required. Nothing in the Constitution ties
Congress to the typical structure of appellate review es-
tablished by statute. If Congress wishes to make certain
rulings reviewable by a single circuit judge, rather than a
panel of three, the Constitution does not stand in the way.
                             III
   Satisfied that we have jurisdiction, we turn to the ques-
tion whether the Court of Appeals applied the correct legal
standard when it affirmed the denial of petitioner’s fund-
ing request.
   Section 3599(a) authorizes federal courts to provide
funding to a party who is facing the prospect of a death
sentence and is “financially unable to obtain adequate
representation or investigative, expert, or other reason-
ably necessary services.” The statute applies to defendants
in federal cases, §3599(a)(1), as well as to state and federal
prisoners seeking collateral relief in federal court,
§3599(a)(2).
   Here we are concerned not with legal representation but
with services provided by experts, investigators, and the
like. Such services must be “reasonably necessary for the
representation of the [applicant]” in order to be eligible for
funding. §3599(f ). If the statutory standard is met, a
court “may authorize the [applicant’s] attorneys to obtain
such services on [his] behalf.” Ibid.
   The Fifth Circuit has held that individuals seeking
funding for such services must show that they have a
“substantial need” for the services. 817 F. 3d, at 896;
                 Cite as: 584 U. S. ____ (2018)           15

                     Opinion of the Court

Allen v. Stephens, 805 F. 3d 617, 626 (2015); Ward v.
Stephens, 777 F. 3d 250, 266, cert. denied, 577 U. S. ___
(2015). Petitioner contends that this interpretation is
more demanding than the standard—“reasonably neces-
sary”—set out in the statute. And although the difference
between the two formulations may not be great, petitioner
has a point.
   In the strictest sense of the term, something is “neces-
sary” only if it is essential. See Webster’s Third New
International Dictionary 1510 (1993) (something is neces-
sary if it “must be by reason of the nature of things,” if it
“cannot be otherwise by reason of inherent qualities”); 10
Oxford English Dictionary 275–276 (2d ed. 1989) (OED)
(defining the adjective “necessary” to mean “essential”).
But in ordinary speech, the term is often used more loosely
to refer to something that is merely important or strongly
desired. (“I need a vacation.” “I need to catch up with an
old friend.”) The term is sometimes used in a similar way
in the law. The term “necessary” in the Necessary and
Proper Clause does not mean “absolutely necessary,”
McCulloch v. Maryland, 4 Wheat. 316, 414–415 (1819),
and a “necessary” business expense under the Internal
Revenue Code, 26 U. S. C. §162(a), may be an expense
that is merely helpful and appropriate, Commissioner v.
Tellier, 383 U. S. 687, 689 (1966). As Black’s Law Diction-
ary puts it, the term “may import absolute physical neces-
sity or inevitability, or it may import that which is only
convenient, useful, appropriate, suitable, proper, or condu-
cive to the end sought.” Black’s Law Dictionary 928 (5th
ed. 1979) (Black’s).
   Section 3599 appears to use the term “necessary” to
mean something less than essential. The provision applies
to services that are “reasonably necessary,” but it makes
little sense to refer to something as being “reasonably
essential.” What the statutory phrase calls for, we con-
clude, is a determination by the district court, in the exer-
16                   AYESTAS v. DAVIS

                     Opinion of the Court

cise of its discretion, as to whether a reasonable attorney
would regard the services as sufficiently important, guided
by the considerations we set out more fully below.
   The Fifth Circuit’s test—“substantial need”—is arguably
more demanding. We may assume that the term “need” is
comparable to “necessary”—that is, that something is
“needed” if it is “necessary.” But the term “substantial”
suggests a heavier burden than the statutory term “rea-
sonably.” Compare 13 OED 291 (defining “reasonably” to
mean, among other things, “[s]ufficiently, suitably, fairly”;
“[f ]airly or pretty well”) with 17 id., at 66–67 (defining
“substantial,” with respect to “reasons, causes, evidence,”
to mean “firmly or solidly established”); see also Black’s
1456 (10th ed. 2014) (defining “reasonable” to mean
“[f ]air, proper, or moderate under the circumstances . . .
See plausible”); id., at 1656 (defining “substantial” to
mean, among other things, “[i]mportant, essential, and
material”).
   The difference between “reasonably necessary” and
“substantially need[ed]” may be small, but the Fifth Cir-
cuit exacerbated the problem by invoking precedent to the
effect that a habeas petitioner seeking funding must pre-
sent “a viable constitutional claim that is not procedurally
barred.” 817 F. 3d, at 895 (internal quotation marks
omitted). See also, e.g., Riley v. Dretke, 362 F. 3d 302, 307
(CA5 2004) (“A petitioner cannot show a substantial need
when his claim is procedurally barred from review”);
Allen, supra, at 638–639 (describing “ ‘our rule that a
prisoner cannot show a substantial need for funds when
his claim is procedurally barred from review’ ” (quoting
Crutsinger v. Stephens, 576 Fed. Appx. 422, 431 (CA5
2014) (per curiam)); Ward, supra, at 266 (“The denial of
funding will be upheld . . . when the constitutional claim is
procedurally barred”).
   The Fifth Circuit adopted this rule before our decision in
Trevino, but after Trevino, the rule is too restrictive.
                  Cite as: 584 U. S. ____ (2018)           17

                      Opinion of the Court

Trevino permits a Texas prisoner to overcome the failure
to raise a substantial ineffective-assistance claim in state
court by showing that state habeas counsel was ineffec-
tive, 569 U. S., at 429, and it is possible that investigation
might enable a petitioner to carry that burden. In those
cases in which funding stands a credible chance of ena-
bling a habeas petitioner to overcome the obstacle of pro-
cedural default, it may be error for a district court to
refuse funding.
   Congress has made it clear, however, that district courts
have broad discretion in assessing requests for funding.
Section 3599’s predecessor declared that district courts
“shall authorize” funding for services deemed “reasonably
necessary.” 21 U. S. C. §848(q)(9) (1988 ed.). Applying
this provision, courts of appeals reviewed district court
funding decisions for abuse of discretion. E.g., Bonin v.
Calderon, 59 F. 3d 815, 837 (CA9 1995); In re Lindsey, 875
F. 2d 1502, 1507, n. 4 (CA11 1989); United States v. Alden,
767 F. 2d 314, 319 (CA7 1984). Then, as part of the Anti-
terrorism and Effective Death Penalty Act of 1996, 110
Stat. 1226, Congress changed the verb from “shall” to
“may,” and thus made it perfectly clear that determining
whether funding is “reasonably necessary” is a decision as
to which district courts enjoy broad discretion. See King-
domware Technologies, Inc. v. United States, 579 U. S. ___,
___ (2016) (slip op., at 9).
   A natural consideration informing the exercise of that
discretion is the likelihood that the contemplated services
will help the applicant win relief. After all, the proposed
services must be “reasonably necessary” for the applicant’s
representation, and it would not be reasonable—in fact, it
would be quite unreasonable—to think that services are
necessary to the applicant’s representation if, realistically
speaking, they stand little hope of helping him win relief.
Proper application of the “reasonably necessary” standard
thus requires courts to consider the potential merit of the
18                    AYESTAS v. DAVIS

                      Opinion of the Court

claims that the applicant wants to pursue, the likelihood
that the services will generate useful and admissible
evidence, and the prospect that the applicant will be able
to clear any procedural hurdles standing in the way.
    To be clear, a funding applicant must not be expected to
prove that he will be able to win relief if given the services
he seeks. But the “reasonably necessary” test requires an
assessment of the likely utility of the services requested,
and §3599(f ) cannot be read to guarantee that an appli-
cant will have enough money to turn over every stone.
    Petitioner does not deny this. He agrees that an appli-
cant must “articulat[e] specific reasons why the services
are warranted”—which includes demonstrating that the
underlying claim is at least “ ‘plausible’ ”—and he
acknowledges that there may even be cases in which it
would be within a court’s discretion to “deny funds after a
finding of ‘reasonable necessity.’ ” Brief for Petitioner 43.
    These interpretive principles are consistent with the
way in which §3599’s predecessors were read by the lower
courts. See, e.g., Alden, supra, at 318–319 (explaining
that it was “appropriate for the district court to satisfy
itself that [the] defendant may have a plausible defense
before granting the defendant’s . . . motion for psychiatric
assistance to aid in that defense,” and that it is not proper
to use the funding statute to subsidize a “ ‘fishing expedi-
tion’ ”); United States v. Hamlet, 480 F. 2d 556, 557 (CA5
1973) (per curiam) (upholding District Court’s refusal to
fund psychiatric services based on the District Court’s
conclusion that “the request for psychiatric services was
. . . lacking in merit” because there was “no serious possi-
bility that appellant was legally insane at any time perti-
nent to the crimes committed”). This abundance of prece-
dent shows courts have plenty of experience making the
determinations that §3599(f ) contemplates.
                 Cite as: 584 U. S. ____ (2018)                 19

                     Opinion of the Court

                             IV
   Perhaps anticipating that we might not accept the Fifth
Circuit’s reading of §3599(f ), respondent devotes a sub-
stantial portion of her brief to an alternative ground for
affirmance that was neither presented nor passed on
below.
   Respondent contends that whatever “reasonably neces-
sary” means, funding is never “reasonably necessary” in a
case like this one, where a habeas petitioner seeks to
present a procedurally defaulted ineffective-assistance-of-
trial-counsel claim that depends on facts outside the state-
court record. Citing 28 U. S. C. §2254(e)(2), respondent
contends that the fruits of any such investigation would be
inadmissible in a federal habeas court.
   We decline to decide in the first instance whether re-
spondent’s reading of §2254(e)(2) is correct. Petitioner
agrees that the argument remains open for the Fifth
Circuit to consider on remand. Tr. of Oral Arg. 6.
                        *    *     *
  We conclude that the Fifth Circuit’s interpretation of
§3599(f ) is not a permissible reading of the statute. We
therefore vacate the judgment below and remand the case
for further proceedings consistent with this opinion.

                                                  It is so ordered.
                  Cite as: 584 U. S. ____ (2018)            1

                   SOTOMAYOR, J., concurring

SUPREME COURT OF THE UNITED STATES
                          _________________

                          No. 16–6795
                          _________________


 CARLOS MANUEL AYESTAS, AKA DENNIS ZELAYA

 COREA, PETITIONER v. LORIE DAVIS, DIRECTOR, 

  TEXAS DEPARTMENT OF CRIMINAL JUSTICE, 

    CORRECTIONAL INSTITUTIONS DIVISION

 ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF 

            APPEALS FOR THE FIFTH CIRCUIT

                        [March 21, 2018]


    JUSTICE SOTOMAYOR, with whom JUSTICE GINSBURG
joins, concurring.
    The Court correctly concludes that the Fifth Circuit
applied the wrong legal standard in evaluating a request
for funding for investigative services under 18 U. S. C.
§3599(f ). That should come as no surprise, as the Fifth
Circuit required capital habeas petitioners to show a
“ ‘substantial need’ ” for services, when the statute requires
only a showing that the services are “ ‘reasonably neces-
sary.’ ” Ante, at 16. “Substantial,” of course, imposes a
higher burden than “reasonable.” Ante, at 16. The Fifth
Circuit “exacerbated the problem” by requiring a showing
of “a viable constitutional claim that is not procedurally
barred,” which ignores “that investigation might enable a
petitioner . . . to overcome the obstacle of procedural de-
fault.” Ante, at 16–17 (internal quotation marks omitted).
I therefore join the opinion of the Court in full holding
that to satisfy §3599(f ), a petitioner need only show that
“a reasonable attorney would regard the services as suffi-
ciently important.” Ante, at 16.
    Having answered the question presented of what is the
appropriate §3599(f ) standard, the Court remands Ayes-
tas’ case for the lower courts to consider the application of
2                       AYESTAS v. DAVIS

                     SOTOMAYOR, J., concurring

the standard in the first instance. Ante, at 19.1 I write
separately to explain why, on the record before this Court,
there should be little doubt that Ayestas has satisfied
§3599(f ).
                               I
   At the center of the §3599(f ) funding request in this
case is Ayestas’ claim that his trial counsel was ineffective
for failing to investigate mitigation. Specifically, Ayestas
claims that his trial counsel was deficient in failing to
conduct an investigation of his mental health and sub-
stance abuse, which could have been presented at the
penalty phase of the trial to convince the jury to spare his
life. As the Court notes, however, Ayestas faces a hurdle
in presenting this ineffective-assistance-of-trial-counsel
claim in his federal habeas petition, as his state postcon-
viction counsel never presented that claim in the Texas
collateral proceedings. See ante, at 5.
   To overcome that procedural default, Ayestas relies on
Martinez v. Ryan, 566 U. S. 1 (2012), and Trevino v. Thaler,
569 U. S. 413 (2013). In those cases, this Court recognized
a “particular concern” in the application of a procedural
default rule that would prevent a petitioner from “pre-
sent[ing] a claim of trial error,” especially “when the claim
is one of ineffective assistance of counsel.” Martinez, 566
U. S., at 12. “The right to the effective assistance of coun-
sel,” the Court reasoned, “is a bedrock principle in our
justice system.” Ibid. The Court thus held that where the
“state procedural framework, by reason of its design and
operation, makes it highly unlikely in a typical case that a
defendant will have a meaningful opportunity to raise a
claim of ineffective assistance of trial counsel on direct
appeal,” then “ ‘a procedural default will not bar a federal

——————
  1 The Court also declines to consider arguments that respondent ad-

vanced that were neither presented nor passed on below. Ante, at 19.
                     Cite as: 584 U. S. ____ (2018)                    3

                       SOTOMAYOR, J., concurring

habeas court from hearing a substantial claim of ineffec-
tive assistance at trial if, in the initial-review collateral
proceeding, there was no counsel or counsel . . . was inef-
fective.’ ” Trevino, 569 U. S., at 429 (quoting Martinez, 566
U. S., at 17; alteration omitted).2
   Therefore, the fact that Ayestas’ postconviction counsel
failed to raise his ineffective-assistance-of-trial-counsel
claim in state court does not bar federal review of that
claim if Ayestas can show that the “attorney in his first
collateral proceeding was ineffective” and that “his claim
of ineffective assistance of trial counsel is substantial.”
Id., at 18. The substantiality of the ineffective-assistance-
of-trial-counsel claim and the ineffectiveness of postconvic-
tion counsel are both analyzed under the familiar frame-
work set out in Strickland v. Washington, 466 U. S. 668
(1984). “Ineffective assistance under Strickland is defi-
cient performance by counsel resulting in prejudice, with
performance being measured against an objective standard
of reasonableness.” Rompilla v. Beard, 545 U. S. 374, 380
(2005) (citation and internal quotation marks omitted).
   Remember, however, the specific context in which inef-
fective assistance is being considered in Ayestas’ case: a
request under §3599(f ) for investigative services, which
requires a showing only that “a reasonable attorney would
regard the services as sufficiently important.” Ante, at 16.
Ayestas is not “expected to prove that he will be able to
win relief if given the services he seeks.” Ante, at 18

——————
  2 The reason for this exception is evident. Excusing the procedural

default “acknowledges, as an equitable matter, that the initial-review
collateral proceeding, if undertaken without counsel or with ineffective
counsel, may not have been sufficient.” Martinez, 566 U. S., at 14.
“Claims of ineffective assistance at trial often require investigative
work and an understanding of trial strategy,” and “the prisoner is in no
position to develop the evidentiary basis for a claim of ineffective
assistance, which often turns on evidence outside the trial record.” Id.,
at 11–12; see also Trevino, 569 U. S., at 423–424, 428.
4                        AYESTAS v. DAVIS

                      SOTOMAYOR, J., concurring

(emphasis in original). A court simply must consider at
this stage “the potential merit of the claims that the appli-
cant wants to pursue, the likelihood that the services will
generate useful and admissible evidence, and the prospect
that the applicant will be able to clear any procedural
hurdles standing in the way.” Ante, at 17–18. Thus, the
inquiry is not whether Ayestas can prove that his trial
counsel was ineffective under Strickland or whether he
will succeed in overcoming the procedural default under
Martinez and Trevino. Rather, at this §3599(f ) request
stage, the focus is on the potential merit of these claims.
                             II

                             A

  With this framework in mind, the focus first is on the
evidence of the deficient performance of Ayestas’ state-
appointed counsel.3 Trial counsel secured the appoint-
ment of an investigator, who met with Ayestas shortly
after the appointment. For nearly 15 months, however,
there was apparently no investigation into Ayestas’ history
in preparation for trial. Counsel instructed the investi-
gator “to resume investigation” only about a month before
jury selection. Record 878. The investigator then subpoe-
naed psychological and disciplinary prison records and
had Ayestas fill out a questionnaire, in response to which
Ayestas revealed that he had experienced multiple head
traumas and had a history of substance abuse. Jail rec-
ords also noted a rules infraction for possession of home-
made intoxicants. Trial counsel never followed up on any
of this information, sought further related records, or had
Ayestas evaluated by a mental health professional.
  About two weeks before jury selection, trial counsel for
the first time reached out to Ayestas’ family in Honduras.

——————
  3 The State appointed two attorneys to represent Ayestas at trial. I

refer to them together as “trial counsel.”
                    Cite as: 584 U. S. ____ (2018)                   5

                      SOTOMAYOR, J., concurring

Shortly thereafter, five days before trial, counsel wrote
Ayestas’ family stating that she needed them to come
testify. Ayestas’ family agreed, but they indicated that
they could not obtain visas because a letter that trial
counsel was supposed to have sent to the U. S. Embassy to
facilitate their travel never arrived, and ultimately no
family members appeared at Ayestas’ trial.
   The guilt phase lasted two days, and trial counsel pre-
sented no witnesses. The penalty phase lasted less than a
day, and trial counsel presented two minutes of mitigation
evidence consisting of three letters from an instructor who
taught English classes to Ayestas in prison, attesting that
he was “a serious and attentive student.” App. 41–43.4
   On this record, Ayestas has made a strong showing that
trial counsel was deficient. “It is unquestioned that under
the prevailing professional norms at the time of [Ayestas’]
trial, counsel had an obligation to conduct a thorough
investigation of [his] background.” Porter v. McCollum,
558 U. S. 30, 39 (2009) (per curiam) (internal quotation
marks omitted). Here, Ayestas’ trial counsel “clearly did
not satisfy those norms.” Ibid. With a client facing a
possible death sentence, counsel and her investigator did
not start looking into Ayestas’ personal history until the
eve of trial. The little the investigator uncovered—head
trauma and a history of substance abuse—should have
prompted further inquiry. Yet trial counsel did nothing.
Even if Ayestas prohibited counsel from contacting his
family in Honduras until the start of trial was imminent,
see ante, at 3,5 that still would not explain why counsel
——————
  4 Trial counsel also attempted to introduce evidence that Ayestas had

no criminal history in Honduras, but failed to link Ayestas to the
records, which were under his given name, “Dennis Zelaya Corea.” See
Ayestas v. Stephens, 817 F. 3d 888, 892, n. 1 (CA5 2016) (per curiam).
  5 During postconviction proceedings, trial counsel filed an affidavit

asserting that Ayestas did not allow contact with his family in Hondu-
ras until after jury selection had commenced. When the record evi-
6                         AYESTAS v. DAVIS

                       SOTOMAYOR, J., concurring

failed to perform any other mitigation investigation, see
Porter, 558 U. S., at 40 (noting that even if the defendant
is “uncooperative, . . . that does not obviate the need for
defense counsel to conduct some sort of mitigation investi-
gation (emphasis in original)). In the end, the decision to
sentence Ayestas to death was made in less than one day,
and his counsel spent less than two minutes presenting
mitigation to the jury. Two minutes.
  This Court has recognized that the decision not to pre-
sent mitigation may be supported in certain cases by
“strategic judgments,” provided the reviewing court is
satisfied with “the adequacy of the investigations support-
ing those judgments.” Wiggins v. Smith, 539 U. S. 510,
521 (2003). But this does not appear to be one of those
cases. There is nothing in the record that would support
the conclusion that counsel chose the two-minutes-of-
mitigation strategy after careful investigation and consid-
eration of Ayestas’ case. Instead, counsel for the most part
“did not even take the first step of interviewing witnesses
or requesting records” and “ignored pertinent avenues for
investigation of which [they] should have been aware.”
Porter, 558 U. S., at 39–40.
  In evaluating the potential merit of Ayestas’ claim, the
Fifth Circuit misapplied Strickland and the §3599(f )
standard. It reasoned that Ayestas had not presented a
viable claim that trial counsel was deficient in failing to
investigate Ayestas’ mental illness because, as he was not
diagnosed with schizophrenia until his time in prison,
there was nothing that flagged mental illness issues prior
to trial.6 See Ayestas v. Stephens, 817 F. 3d 888, 895–897
——————
dence contradicted that assertion, counsel submitted another affidavit
with a revised timeline. Ayestas disputes having instructed trial
counsel not to contact his family in Honduras.
  6 It is unclear whether the Fifth Circuit ultimately relied on its de-

termination that trial counsel was not deficient in rejecting Ayestas’
claims. In its panel opinion, it incorrectly stated that trial counsel had
                     Cite as: 584 U. S. ____ (2018)                   7

                      SOTOMAYOR, J., concurring

(2016) (per curiam). The absence of a documented diagno-
sis, however, did not excuse trial counsel from their “obli-
gation to conduct a thorough investigation of [Ayestas’]
background.” Porter, 558 U. S., at 39 (internal quotation
marks omitted). In fact, the obligation to investigate
exists in part precisely because it is all too common for
individuals to go years battling an undiagnosed and un-
treated mental illness.
   In any event, the Fifth Circuit failed to consider that
one of the purposes of the §3599(f ) investigation was to
look at Ayestas’ life around the time of the crime and trial
to determine if there were mitigating circumstances that
trial counsel could have discovered, such as whether
symptoms of his schizophrenia had begun to manifest even
before his diagnosis. The Court makes clear today that in
evaluating §3599(f ) funding requests, courts must consider
“the likelihood that the services will generate useful and
admissible evidence.” Ante, at 17. It was error, therefore,
for the Fifth Circuit to evaluate the merit of the ineffec-
tive-assistance-of-trial-counsel claim and to deny §3599(f )
funding based solely on an evaluation of the evidence in
the record at the time of the request, without evaluating
the potential evidence that Ayestas sought. Ante, at
17–18.
                             B
  The evidence concerning the deficiency of Ayestas’ state
postconviction counsel is similarly strong. State postcon-
viction counsel retained the services of a mitigation spe-
cialist, who prepared an investigation plan noting that it
——————
conducted a psychological evaluation of Ayestas. 817 F. 3d, at 897.
After Ayestas corrected the record in his petition for rehearing, the
panel issued an order reaffirming its holding, relying on its finding of
no prejudice. See Ayestas v. Stephens, 826 F. 3d 214, 215 (2016) ( per
curiam). Still, the Fifth Circuit never disavowed its conclusion regard-
ing trial-counsel deficiency. Ibid.
8                     AYESTAS v. DAVIS

                   SOTOMAYOR, J., concurring

was “obvious no social history investigation was conducted”
and that the jury had “heard nothing about [Ayestas’] . . .
mental health, possible mental illness, [or] substance
abuse history.” App. 81, 266. The plan also noted that it
was “clear that [Ayestas] had a history of substance
abuse.” Record 721; see also App. 267. The specialist
recommended a comprehensive investigation into Ayestas’
biological, psychological, and social history to explore,
inter alia, issues related to addiction and mental health.
   State postconviction counsel failed to follow these rec-
ommendations. He did nothing to investigate issues related
to Ayestas’ mental health or substance abuse. Notably,
Ayestas suffered a psychotic episode and was diagnosed
with schizophrenia while his state postconviction applica-
tion was pending. Moreover, in 2003, a counsel-arranged
evaluation pursuant Atkins v. Virginia, 536 U. S. 304
(2002), noted concerns about Ayestas’ “delusional think-
ing.” App. 139–140. These events still did not prompt
counsel to investigate Ayestas’ mental health history.
   Instead, state postconviction counsel explored the cir-
cumstances of Ayestas’ arrest, conducted some juror inter-
views, and interviewed Ayestas’ mother and sisters, ob-
taining affidavits regarding Ayestas’ upbringing in
Honduras and their interactions with trial counsel. Post-
conviction counsel eventually filed an application that
contained a narrow claim of ineffective assistance of trial
counsel with respect to mitigation regarding the attorneys’
failure to secure the attendance of Ayestas’ family mem-
bers at trial. The Texas Court of Criminal Appeals denied
the application, relying on the affidavit submitted by trial
counsel, see n. 4, supra, to find no ineffectiveness in failing
to get Ayestas’ family to attend trial.
   The Fifth Circuit concluded that Ayestas’ state postcon-
viction counsel was not ineffective because, in its view,
Ayestas had not established any deficiency at trial in the
failure to investigate mental health and substance abuse
                 Cite as: 584 U. S. ____ (2018)            9

                   SOTOMAYOR, J., concurring

mitigation. See 817 F. 3d, at 898. That conclusion, as
noted in Part II–A, supra, was based on a misapplication
of Strickland and the §3599(f ) standard, and thus cannot
support a finding that the failure to present the claim in
postconviction proceedings was “strategic.” 817 F. 3d, at
898. Nor is there anything else in the record that would
excuse that deficiency. State postconviction counsel ig-
nored his own mitigation specialist, who alerted him to a
serious failing in the trial because the jury heard virtually
no mitigation and to the serious failings of trial counsel
because of the failure to conduct a social history investiga-
tion of Ayestas. Even after Ayestas’ psychotic episode,
schizophrenia diagnosis, and documented tendencies of
“delusional thinking” during the course of the representa-
tion, state postconviction counsel did nothing. As with
trial counsel, the record provides no support for any “stra-
tegic justification” to disregard completely a mitigation
investigation of Ayestas’ mental health and substance
abuse.
                             III
   Strickland next requires consideration of prejudice. To
establish prejudice, this Court has held that a “defendant
must show that there is a reasonable probability that, but
for counsel’s unprofessional errors, the result of the pro-
ceeding would have been different,” meaning “a probabil-
ity sufficient to undermine confidence in the outcome.”
466 U. S., at 694. In cases alleging a failure to investigate
mitigation, as here, the Court must “reweigh the evidence
in aggravation against the totality of available mitigating
evidence.” Wiggins, 539 U. S., at 534.
   Even with the scant evidence in the record at this time
as to what Ayestas could have presented to the jury in the
form of mitigation, Ayestas has made a strong showing
that his claim has potential merit. That trial counsel
presented only two minutes of mitigation already goes a
10                      AYESTAS v. DAVIS

                     SOTOMAYOR, J., concurring

long way to establishing prejudice.           In fact, the State
emphasized to the jury at sentencing:
     “Does he have anything there that would lead you to
     conclude there is some type of mitigation, anything at
     all? There is no drug problem . . . no health problem
     . . . no alcohol problem. . . . [O]nly . . . these three pieces
     of paper . . . . Making steps to learn a second lan-
     guage does not lessen his moral blameworthiness
     . . . .” Record 4747.
The State, in contrast, presented evidence of Ayestas’
criminal history as well as victim impact testimony. After
deliberating for only 25 minutes, the jury assessed a pun-
ishment of death against Ayestas, finding that he was a
future danger, that he intended to cause death or antici-
pated the loss of life, and that there were no mitigating
circumstances that warranted imposition of a life sentence
over a death sentence. Had just one juror dissented on a
single one of these findings, no death sentence could have
been imposed. See Tex. Code Crim. Proc. Ann., Art.
37.071, §2(g) (Vernon Cum. Supp. 2017); see also ante, at
2. With even minimal investigation by trial counsel, at
least one may well have, as this Court has held that evi-
dence of mental illness and substance abuse is relevant to
assessing moral culpability. See Rompilla, 545 U. S., at
393; Porter, 558 U. S., at 43–44. Instead, the jury “heard
almost nothing that would humanize [him] or allow them
to accurately gauge his moral culpability.” Id., at 41.
There is thus good reason to believe that, were Ayestas’
§3599(f ) motion granted, he could establish prejudice
under Strickland.
   The Fifth Circuit held otherwise based on its belief that
no amount of mitigation would have changed the outcome
of the sentencing given the “brutality of the crime.” 817
F. 3d, at 898. That “brutality of the crime” rationale is
simply contrary to our directive in case after case that, in
                     Cite as: 584 U. S. ____ (2018)                    11

                       SOTOMAYOR, J., concurring

assessing prejudice, a court must “consider the totality of
the available mitigation evidence . . . and reweigh it
against the evidence in aggravation.” Porter, 558 U. S., at
41 (internal quotation marks and alterations omitted); see
also Williams v. Taylor, 529 U. S. 362, 397–398 (2000);
Wiggins, 539 U. S., at 534. By considering aggravation in
isolation, the Fifth Circuit directly contravened this fun-
damental principle.7
                              IV
  In sum, Ayestas has made a strong showing that he is
entitled to §3599(f ) funding. As the Court notes, the
statute affords district courts some discretion in these
funding determinations, even where a petitioner shows
the services are “ ‘reasonably necessary.’ ” Ante, at 17–18.
Exercise of that discretion may be appropriate if there is a
showing of gamesmanship or where the State has provided
funding for the same investigation services, as Ayestas
conceded at argument. See Tr. of Oral Arg. 13. Nonethe-
less, the troubling failures of counsel at both the trial and
state postconviction stages of Ayestas’ case are exactly the
types of facts that should prompt courts to afford investi-
gatory services to ensure that trial errors that go to a
“bedrock principle in our justice system” do not go un-
addressed. Martinez, 566 U. S., at 12.




——————
  7 Notably, application of this “brutality of the crime” rule is particu-

larly irrational in the §3599(f ) context, where the court is unaware of
what the undiscovered evidence of mitigation looks like.
