                     FOR PUBLICATION
  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT

BENJAMIN WAI SILVA,                               No. 04-99000
             Petitioner-Appellant,
               v.                                   D.C. No.
                                                  CV-90-03311-DT
JILL BROWN, Warden,*
                                                     OPINION
             Respondent-Appellee.
                                            
        Appeal from the United States District Court
            for the Central District of California
       Dickran M. Tevrizian, District Judge, Presiding

                   Argued and Submitted
          March 22, 2005—San Francisco, California

                        Filed July 26, 2005

      Before: Betty B. Fletcher, Sidney R. Thomas, and
           Kim McLane Wardlaw, Circuit Judges.

                  Opinion by Judge B. Fletcher




  *Jill Brown is substituted for her predecessor, Jeanne Woodford, pursu-
ant to Fed. R. App. P. 43(c)(2).

                                 8615
8618                   SILVA v. BROWN


                        COUNSEL

Phillip A. Treviño, Los Angeles, California, argued for the
petitioner-appellant. With him on the briefs was Michael J.
Brennan, Manhattan Beach, California.

Teresa Torreblanca, San Diego, California, argued for the
respondent-appellee. Robert M. Foster, San Diego, California,
was on the brief.
                         SILVA v. BROWN                    8619
                          OPINION

B. FLETCHER, Circuit Judge:

   The State of California charged and tried Benjamin Wai
Silva for two brutal homicides, along with kidnaping, rob-
bery, and gun offenses, but did not disclose to the defense that
the plea agreement that secured the testimony of the prosecu-
tion’s star witness, Norman Thomas, required Thomas not to
undergo a psychiatric evaluation before testifying. As a result,
the jury never learned of the considerable question as to
Thomas’s competence to testify or of the secret deal the Las-
sen County District Attorney made to ensure that question
remained unanswered until after Silva was tried. At issue in
this appeal is whether the failure to disclose that deal was
Brady error. We conclude that it was.

                    I.   BACKGROUND

   Silva’s case is before us for the second time. On our first
consideration of the case, we remanded for the district court
to determine whether there was Brady error: was there a deal
such as Silva alleged; if so, did the prosecutor conceal it; and
if he did, were the deal and its concealment material under
Brady? Silva v. Woodford, 279 F.3d 825, 855 (9th Cir. 2002)
(“Silva I”). The district court found that there was a deal and
that it was not disclosed, but found that these facts were
immaterial to Silva’s conviction. It is this judgment that Silva
now appeals.

   As the facts and procedural background are amply summa-
rized in our prior disposition, we excerpt from that summary
as relevant to the issues before us here and add additional
details as necessary.

      Silva stands convicted of the gruesome abduction,
    robbery and murder of [Kevin] Thorpe in Madeline,
    California. Thorpe and his girlfriend, Laura Craig,
8620                   SILVA v. BROWN
    were college students returning from winter break
    when they passed through Madeline on their way to
    Oregon. On January 11, 1981, Silva and two accom-
    plices, Joe Shelton and Norman Thomas, kidnaped
    Thorpe and Craig after spotting the couple at a fill-
    ing station in town. The three men forced the couple
    to drive to Shelton’s property and proceeded to take
    their cash and belongings. Thorpe was then chained
    to a tree while Craig was taken inside a cabin and
    repeatedly sexually assaulted.

Id. at 828.

  Thorpe was subsequently shot and killed. Thomas, by his
own admission, then dismembered Thorpe’s body with an axe
and buried the remains in shallow graves. Craig was later shot
and killed by the side of a road.

       Thomas informed police of the murders later that
    month after being found in possession of a firearm
    in violation of his probation. In exchange for turning
    state’s evidence, murder charges against Thomas
    were dropped. He was eventually sentenced to
    eleven years and four months imprisonment for par-
    ticipating in the kidnaping, being an accessory after
    the fact to murder, burglary, and use of a firearm.

      Shelton’s trial took place before Silva’s. He was
    convicted of murdering both Thorpe and Craig and
    sentenced to life without parole. On direct appeal, he
    was resentenced to life imprisonment.

       Because of publicity, Silva’s trial was held in San
    Bernardino County in January 1982. When called to
    testify at Silva’s trial, Shelton invoked his Fifth
    Amendment privilege against self-incrimination. The
    primary evidence regarding Silva’s role in Thorpe’s
    death came from Thomas. Thomas testified that both
                   SILVA v. BROWN                       8621
Silva and Shelton left the cabin in the morning after
the kidnapings, and that Thorpe was murdered while
Thomas was having consensual sex with Craig.
According to Thomas, Silva then returned to the
cabin and forced Thomas to dismember and dispose
of Thorpe’s body. Subsequently, the three men were
standing over a barrel in which some of Thorpe’s
belongings were being burned, when Shelton alleg-
edly proceeded to describe to Thomas how Thorpe
had died. Shelton related how he and Silva had
unlocked the chain linking Thorpe to the tree and led
him terrified and crying up the side of a hill. After
leaving briefly to obtain a weapon, Silva then
walked up behind Thorpe and shot him up and down
his body at close range, using an Ingram M-11 .38
caliber fully automatic pistol equipped with a
silencer. Silva then gave the weapon to Shelton, who
emptied the rest of the magazine clip into Thorpe’s
body. According to Thomas, Silva simply looked on
and smiled as Shelton described the slaying to
Thomas.

   Thomas also testified that several days after
Craig’s disappearance, a similar conversation took
place while the three were gathered on the porch of
the cabin, in which Shelton described how Craig had
been shot and killed. Once again, Silva allegedly
looked on and smiled while Shelton spoke to
Thomas.

  At the conclusion of the guilt phase, the jury
deliberated for two days before finding Silva guilty
of first-degree murder in the shooting death of
Thorpe. However, the jury found Silva not guilty of
Craig’s murder. The jury also found Silva guilty of
kidnaping and robbing both victims, as well as ille-
gally possessing a machine gun and a silencer.
8622                    SILVA v. BROWN
Id. at 828-29.

   At the penalty phase, the jury returned a verdict of death.
Silva also received two life sentences for the two kidnaping
convictions, along with a variety of lesser sentences for the
other convictions. On direct appeal, the state courts substan-
tially affirmed the verdict and the death sentence. After two
state habeas petitions were summarily denied, Silva filed a
federal habeas petition in 1990 and a second amended petition
in 1993.

   One of Silva’s claims on federal habeas is that the prosecu-
tion violated his due process rights under Brady v. Maryland,
373 U.S. 83 (1963), by failing to disclose to the defense that
the prosecution’s deal with its chief witness Norman Thomas
had required that Thomas, who had several years earlier been
involved in a motorcycle accident and suffered severe brain
damage, not undergo a psychiatric evaluation before testifying
against Silva. Silva also claimed, among other things, that he
had received ineffective assistance of counsel at the guilt and
penalty phases of his trial. In 1999, the district court denied
Silva’s petition in its entirety.

   On appeal, we affirmed the district court in part, reversed
in part, and remanded. We held that relief should be granted
on Silva’s ineffective assistance claim with regard to the pen-
alty phase, but we rejected Silva’s claims of ineffective assis-
tance with regard to the guilt phase. Silva I, 279 F.3d at 855.
With respect to the Brady claim, we determined that Norman
Thomas’s credibility was “a critical issue, given that he was
the only witness who could identify Silva as the trigger man
in Thorpe’s murder.” Id. at 854-55. Had the prosecution’s
deal prohibiting a psychiatric examination of Thomas been
presented to the jury, we concluded, the very fact of the deal
(if true) “could by itself have undermined Thomas’s credibili-
ty” by making the jury aware of “the potentially devastating
fact that the state itself doubted Thomas’s mental competen-
cy.” Id. at 855. We therefore remanded the case for an eviden-
                        SILVA v. BROWN                      8623
tiary hearing as to the veracity of Silva’s allegations regarding
the prosecution’s secret deal with Norman Thomas. In accor-
dance with our disposition of Silva’s penalty phase ineffective
assistance claim, we ordered that Silva be resentenced follow-
ing the exhaustion of the current habeas petition. Id. at 856.

   On remand to the district court, Silva’s allegations regard-
ing the undisclosed deal were established as true. Thomas’s
attorney, Rex Gay, stated in his declaration that at the time of
Thomas’s arraignment, he had imminent plans to have
Thomas psychiatrically evaluated, because he believed
Thomas “was either unable to cooperate in his own defense,
or insane.” Gay made his plans known to the district attorney,
who agreed with Gay that Thomas’s testimony would be nec-
essary to convict Silva (and Shelton), and that having Thomas
psychiatrically evaluated would “supply ammunition to the
defense.” Gay and the district attorney then struck a bargain
under which Thomas would not be psychiatrically examined,
and in return the district attorney would drop the murder
charges in exchange for Thomas’s testimony.

   Silva’s trial counsel, Thomas Buckwalter, stated in his dec-
laration that, during his representation of Silva, he was never
informed of Thomas’s agreement to refrain from undergoing
a psychiatric evaluation; Buckwalter did not learn of the
agreement until after the trial ended. As the state submitted no
evidence contradicting the Gay and Buckwalter declarations,
the district court found that the evidence

    compels a finding that the prosecutor reached an
    agreement with Thomas prior to Silva’s trial accord-
    ing to which Thomas would refrain from being psy-
    chiatrically examined and would testify at Silva’s
    trial, in exchange for not being charged with murder
    and receiving a total sentence of not more than
    eleven years and four months . . . . [T]he aspect of
    the agreement concerning postponing any psychiat-
8624                     SILVA v. BROWN
      ric examination of Thomas was neither revealed to
      the defense nor disclosed to the jury.

   The district court nonetheless rejected Silva’s Brady claim.
First, the district court found that Thomas’s testimony had
already been adequately called into question on cross-
examination because Thomas had told the jury he would be
receiving a reduced sentence in exchange for his testimony,
then admitted on cross-examination that murder charges could
still be filed against him if he did not cooperate and that Shel-
ton had told him to place all the blame on Silva. According
to the district court, the jury’s decision to acquit Silva for the
murder of Laura Craig — in spite of Thomas’s testimony
implicating Silva for her murder as well as Kevin Thorpe’s —
“demonstrates that the jury did not accept all of Thomas’s tes-
timony at face value, but considered it only to the extent that
it was corroborated by other evidence at trial.” The district
court noted the evidence corroborating significant portions of
Thomas’s story: in particular, the authorities found body parts
and evidence of the kidnaping where Thomas said they would
be, and Silva’s fingerprints were found on ammunition in a
trailer on the Shelton property. Finally, the district court
found that Silva’s vague and equivocating statements to the
police after his arrest provided additional evidence of his
guilt. For these reasons, the district court concluded that the
prosecution’s failure to disclose its agreement regarding the
psychiatric examination of Thomas was not material under
Brady. The district court therefore denied relief on this claim.

II.    JURISDICTION AND STANDARDS OF REVIEW

   This habeas petition was filed before the effective date of
the Antiterrorism and Effective Death Penalty Act of 1996
(“AEDPA”). Silva I, 279 F.3d at 830, 831 n.5. A certificate
of appealability is required for this appeal, but Silva’s case is
in all other respects governed by pre-AEDPA law. Id. at 831
& n.5; accord, Hayes v. Brown, 399 F.3d 972, 978 (9th Cir.
2005) (en banc). Under pre-AEDPA standards, “state court
                        SILVA v. BROWN                      8625
judgments of conviction and sentence carry a presumption of
finality and legality and may be set aside only when a state
prisoner carries his burden of proving that his detention vio-
lates the fundamental liberties of the person, safeguarded
against state action by the Federal Constitution.” Hayes, 399
F.3d at 978 (citation and alteration omitted).

   The district court having issued a certificate of appeala-
bility, we have jurisdiction under 28 U.S.C. § 2253.

  We review Brady claims de novo. United States v. Blanco,
392 F.3d 382, 387 (9th Cir. 2004).

                      III.   ANALYSIS

   [1] The government violates its constitutional duty to dis-
close material exculpatory evidence where (1) the evidence in
question is favorable to the accused in that it is exculpatory
or impeachment evidence, (2) the government willfully or
inadvertently suppresses this evidence, and (3) prejudice
ensues from the suppression (i.e., the evidence is “material”).
See Banks v. Dretke, 540 U.S. 668, 691 (2004); Strickler v.
Greene, 527 U.S. 263, 281-82 (1999); Kyles v. Whitley, 514
U.S. 419, 433 (1995). Evidence is material for Brady pur-
poses “if there is a reasonable probability that, had the evi-
dence been disclosed to the defense, the result of the
proceeding would have been different.” Kyles, 514 U.S. at
433 (citations and internal quotation marks omitted); see also
Banks, 540 U.S. at 699; Strickler, 527 U.S. at 280.

   [2] In applying the materiality standard, the Supreme Court
has explained that “[t]he question is not whether the defen-
dant would more likely than not have received a different ver-
dict with the evidence, but whether in its absence he received
a fair trial, understood as a trial resulting in a verdict worthy
of confidence.” Kyles, 514 U.S. at 434. Thus materiality does
not require a showing that the defendant would have been
acquitted had the suppressed evidence been disclosed, or that
8626                         SILVA v. BROWN
disclosure of the suppressed evidence would have reduced the
quantum of inculpatory evidence below that required to con-
vict the defendant. Id. at 434-35 (stressing that materiality “is
not a sufficiency of evidence test”). Rather, a Brady violation
is established where “the favorable evidence could reasonably
be taken to put the whole case in such a different light as to
undermine confidence in the verdict.” Id. at 435.

   Once the materiality of the suppressed evidence is estab-
lished, no further harmless error analysis is necessary, even in
the context of habeas review: when the government has sup-
pressed material evidence favorable to the defendant, the con-
viction must be set aside. Kyles, 514 U.S. at 435-36; Hayes,
399 F.3d at 984-85.1

   [3] In Silva’s case, the first two Brady elements — that the
evidence is favorable to the accused and that it has been sup-
pressed by the government — have been established. The dis-
trict court found (and the State does not dispute) that the
prosecution made a deal requiring that its witness Norman
Thomas refrain from undergoing a psychiatric evaluation
before testifying against Silva. The existence of this deal evi-
dencing the prosecution’s concern as to the mental state of
Thomas was obviously impeachment evidence favorable to
the defense. The deal was never disclosed to the defense. The
only question the parties debate is whether it was material.

  We answer this question in the affirmative. “We cannot
overemphasize the importance of allowing a full and fair
  1
    Although Hayes addressed claims that the prosecution violated due
process by using and by failing to correct false evidence, Hayes, 399 F.3d
at 978 (citing Napue v. Illinois, 360 U.S. 264 (1959), and Alcorta v. Texas,
355 U.S. 28 (1957)), rather than by failing to disclose material exculpatory
evidence to the defense, Hayes is relevant to Silva’s case because the same
materiality analysis applies to these types of claims. See id. at 985 (noting
that the materiality standard of United States v. Agurs, 427 U.S. 97 (1976),
a forerunner of Kyles, applies to Napue claims); id. at 988 (referring to the
“Napue/Alcorta/Agurs materiality standard”).
                        SILVA v. BROWN                      8627
cross-examination of government witnesses whose testimony
is important to the outcome of the case.” Silva I, 279 F.3d at
854 (quoting United States v. Brooke, 4 F.3d 1480, 1489 (9th
Cir. 1993)). Had the full extent of the prosecution’s deal with
Norman Thomas been disclosed to the defense, a full cross-
examination of this critical witness would have revealed that
even the prosecution viewed Thomas’s testimony with some
doubt. The existence of the deal would have put Thomas in
a different light for the jury. The legitimate question whether
Thomas was competent, or perhaps insane, creates, in our
minds, a reasonable probability of a different result. In the
absence of disclosure of Thomas’s questionable mental state
to the defense and the jury, the guilty verdict returned on the
murder charge is not one worthy of our confidence.

   [4] We begin with an examination of Norman Thomas’s
role in Silva’s trial. Impeachment evidence is especially likely
to be material when it impugns the testimony of a witness
who is critical to the prosecution’s case. See, e.g., Banks, 540
U.S. at 700 (holding that impeachment evidence was material
where it pertained to a witness whose testimony was “crucial
to the prosecution” and was in the prosecution’s own judg-
ment “of the utmost significance”); Carriger v. Stewart, 132
F.3d 463, 480 (9th Cir. 1997) (en banc) (holding that
impeachment evidence was material where it pertained to “the
prosecution’s star witness”); see also East v. Johnson, 123
F.3d 235, 239 (5th Cir. 1997) (“[W]hen the withheld evidence
would seriously undermine the testimony of a key witness on
an essential issue or there is no strong corroboration, the with-
held evidence has been found to be material.” (emphasis
added) (citation and internal quotation marks omitted)).

   [5] The testimony of Norman Thomas was crucial to the
state’s prosecution of Silva for murder. Though other evi-
dence at trial confirmed Silva’s involvement in the abduction
of Thorpe and Craig and suggested Silva’s recognition of his
own guilt, Norman Thomas was — as both this court and the
district court have previously recognized — the only witness
8628                       SILVA v. BROWN
who provided an account of how Thorpe’s murder took place
and the only witness who identified Silva as his killer. Silva
I, 279 F.3d at 852, 854-55; see also Silva v. Calderon, No. CV
90-3311 DT, slip op. at 10 (C.D. Cal. Jan. 27, 1999) (prior
opinion of the district court, affirmed in part and reversed in
part in Silva I) (“The most devastating evidence against Silva
was Thomas’s testimony informing the jury of the two tales
told by Shelton and Silva’s contemporaneous smile.”). Thom-
as’s testimony as to Joe Shelton’s account of the events and
Silva’s damning response is uncorroborated anywhere else in
the record. Without Thomas, the prosecution had no evidence
of how — or by whom — Thorpe was killed.

   Thomas’s testimony was not only the prosecution’s most
specific evidence about the murder; it was also the most pow-
erful. Silva’s “adoptive admission” of Shelton’s account of
Thorpe’s murder was tantamount to a confession. “As the
Supreme Court has observed: ‘A confession is like no other
evidence. Indeed, the defendant’s own confession is probably
the most probative and damaging evidence that can be admit-
ted against him.’ ” Hayes, 399 F.3d at 986 (quoting Arizona
v. Fulminante, 499 U.S. 279, 296 (1991)) (further citation and
internal quotation marks omitted). Thus Thomas’s account of
the exchange between Silva and Shelton was in more than one
respect the crux of the prosecution’s case against Silva for
Thorpe’s murder. See Silva I, 279 F.3d at 852, 854-55. It fol-
lows that Thomas’s credibility was “a critical issue.” Id. at 854.2

  [6] Had the prosecution’s deal foreclosing a psychiatric
examination of Thomas been revealed, it could have had a
profound effect on the jury’s assessment of Thomas’s testi-
  2
   Given the centrality of Thomas’s testimony to the prosecution’s mur-
der case, the state’s heavy reliance on Strickler v. Greene is misplaced.
“The witness whose impeachment was at issue in Strickler gave testimony
that was in the main cumulative, and hardly significant” to the predicate
facts of the offense. Banks, 540 U.S. at 700 (citation omitted). The same
cannot be said of Norman Thomas, without whose testimony the state
would have had no evidence that Silva killed Thorpe.
                       SILVA v. BROWN                     8629
mony. As we have previously recognized, evidence that calls
into question a witness’s competence to testify is powerful
impeachment material. See, e.g., Benn v. Lambert, 283 F.3d
1040, 1054, 1056 (9th Cir. 2002) (holding that undisclosed
evidence of a crucial government witness’s drug use during
the defendant’s trial was material because it would “reflect on
[that witness’s] competence and credibility as a witness”);
United States v. Service Deli, Inc., 151 F.3d 938, 942-44 (9th
Cir. 1998) (holding that a set of handwritten notes taken by
a government attorney during an interview with the govern-
ment’s key witness was material “most significantly” because
the notes included a statement by the witness that he had sus-
tained a stroke that affected his memory).

   [7] The fact of the undisclosed deal bears critically and
directly on Thomas’s “competence and credibility as a wit-
ness.” See Benn, 283 F.3d at 1056. Had the defense known
that the prosecution had required, as a condition of Thomas’s
plea bargain, that he agree not to be psychiatrically evaluated
before testifying, competent defense counsel would have
ensured that the jury was “made aware of the potentially dev-
astating fact that the state itself doubted Thomas’s mental
competency.” Silva I, 279 F.3d at 855. As a result, the jury
might not have believed the most important piece of Thom-
as’s testimony — his uncorroborated account of Silva’s
“adoptive admission” — because of concerns about Thomas’s
capacity clearly to remember who said what to whom.

   Such concerns would have been exacerbated by other evi-
dence in the record that competent counsel would have
brought out on cross-examination in connection with the
question of Thomas’s competence. In particular, Thomas’s
trial testimony that he was in the cabin with Laura Craig when
Thorpe was killed is in conflict with Thomas’s previous state-
ment to the DA that he was with Silva when Thorpe was
killed. Thomas’s several admissions of confusion during his
direct examination would have assumed greater importance
and presumably been a subject of emphasis for the defense
8630                     SILVA v. BROWN
had the prosecution’s doubts about Thomas’s mental capacity
been revealed. Finally, the very fact that the prosecution had
sought to keep evidence of Thomas’s mental capacity away
from the jury might have diminished the State’s own credibil-
ity as a presenter of evidence.

   [8] In sum, the fact of the prosecution’s undisclosed deal
with Thomas, had it been presented to the jury, would have
put the testimony of this critical witness in a substantially dif-
ferent light, both directly, by casting doubt on the accuracy of
Thomas’s testimony, and indirectly, by inducing the defense
to focus the jury’s attention on Thomas’s lapses and inconsis-
tencies and by calling into question the prosecutor’s faith in
the competence of his own witness. With the murder prosecu-
tion so heavily dependent on Thomas’s testimony, and given
the powerful effect the revelation of the prosecution’s own
doubts about its star witness would likely have had on the
jury, we cannot say that, in the absence of this evidence, Silva
“received a fair trial, understood as a trial resulting in a ver-
dict worthy of confidence.” Kyles, 514 U.S. at 434.

   According to the district court and the State, the impeach-
ment of Thomas that actually occurred at trial was sufficient
to render further impeachment material superfluous. Because
Thomas testified that he would receive a reduced sentence for
his testimony, that murder charges could still be filed against
him if he did not cooperate, and that the co-conspirator Shel-
ton had told him to place all the blame on Silva, the district
court concluded that “it is not reasonably probable that such
additional impeachment evidence [i.e., the undisclosed deal]
would have made a difference to this jury’s assessment of
Silva’s guilt.” Along similar lines, the State urges that “since
the other methods used to impeach Thomas failed, this lesser
tool [i.e., the undisclosed deal] would also have failed.”

   [9] Our precedent rejects this strained logic. The failure of
a defendant’s efforts to impeach a witness does not prove that
additional impeachment would have been ineffectual, or
                       SILVA v. BROWN                     8631
merely cumulative, any more than it supports the opposite
conclusion. As we explained in Benn v. Lambert, a defen-
dant’s conviction in spite of his attempt at impeaching a key
government witness demonstrates only the inadequacy of the
impeachment material actually presented, not that of the sup-
pressed impeachment material; in light of the failure of the
impeachment attempt at trial, the suppressed impeachment
material may “take[ ] on an even greater importance.” 283
F.3d at 1055; see also Service Deli, 151 F.3d at 944 (“It
makes little sense to argue that because [the defendant] tried
to impeach [the witness] and failed, any further impeachment
evidence would be useless. It is more likely that [the defen-
dant] may have failed to impeach [the witness] because the
most damning impeachment evidence in fact was withheld by
the government.”).

   In Benn, we held that the evidence of a witness’s drug use
during trial and history of misconduct was material under
Brady even though the witness had been impeached at trial by
questions about his history as a paid informant, his prior con-
victions, and benefits he received from the state in connection
with his testimony in the case. 283 F.3d at 1054-56. The
undisclosed evidence, we explained, “would have provided
the defense with a new and different ground of impeachment”
than those introduced at trial. Id. at 1056. Likewise, in Car-
riger v. Stewart, we determined that a witness’s long history
of burglaries and of lying to the police was material notwith-
standing the jury’s knowledge that the witness in question
was a burglar testifying with immunity. 132 F.3d at 481-82.
As we stressed there, “the government cannot satisfy its
Brady obligation to disclose exculpatory evidence by making
some evidence available and claiming the rest would be
cumulative. Rather, the government is obligated to disclose
all material information casting a shadow on a government
witness’s credibility.” Id. (citation and internal quotation
marks omitted) (emphasis in original).

   In Silva’s case, the undisclosed evidence was not duplica-
tive of the impeachment evidence actually presented, but
8632                    SILVA v. BROWN
rather was of a different kind. It “would have provided the
defense with a new and different ground of impeachment.”
Benn, 283 F.3d at 1056. Thomas’s admissions on cross-
examination that murder charges could still be filed against
him and that Shelton had instructed him to blame Silva, could
cast doubt only on Thomas’s forthrightness, not his compe-
tence to testify. See Silva I, 279 F.3d at 852. The deal regard-
ing psychiatric evaluation, of course, relates to reliability:
because of questions as to Thomas’s competence, completely
apart from motive, was his testimony reliable?

   [10] We are influenced by the potency of the undisclosed
impeachment material as well as its subject matter. Even
though the jury heard Thomas admit to being confused sev-
eral times during his direct examination, a few moments of
hesitation on the part of a witness recalling year-old events
pale in comparison to the fact that the party proffering the
witness harbors such doubts about his competency that it has
taken affirmative steps to prevent a psychiatric evaluation of
that witness. Cf. Carriger, 132 F.3d at 481 (“[A]lthough the
jury heard [the prosecution’s star witness] Dunbar admit he
had once slapped his stepdaughter, they heard no evidence of
Dunbar’s lifelong history of violence.”). The fact of the undis-
closed deal was not at all cumulative of the impeachment evi-
dence Silva offered at trial; on the contrary, the fact of the
prosecution’s secret deal would have raised new and more
powerful doubts about the reliability of Norman Thomas’s
testimony.

   [11] The prosecutor’s own conduct in keeping the deal
secret underscores the deal’s importance. While the govern-
ment’s Brady obligation exists “irrespective of the good faith
or bad faith of the prosecution,” Banks, 540 U.S. at 691 (cita-
tion and internal quotation marks omitted), we have recog-
nized that a prosecutor’s assessment of undisclosed evidence
can support a finding of materiality by highlighting the impor-
tance of that evidence. For example, in Singh v. Prunty, 142
F.3d 1157 (9th Cir. 1998), we considered the materiality of
                        SILVA v. BROWN                      8633
impeachment evidence the disclosure of which the prosecutor
conceded would have been “the kiss of death” to the govern-
ment’s case. Id. at 1163. We “deem[ed this] candid conces-
sion to be highly significant,” because “the prosecutor, more
than neutral jurists, can better perceive the weakness of the
state’s case.” Id.

   The prosecutor’s actions can speak as loud as his words.
Recently, in considering the materiality of a prosecutor’s
secret agreement to drop felony charges against his star wit-
ness in a capital murder trial, our en banc court found the
prosecutor’s furtive conduct highly relevant: “Presumably, the
importance to the State’s case of [the witness] James’s testi-
mony is what initially led the prosecution to make the secret
deal; likewise, the importance to James’s credibility of his
false testimony regarding the absence of a deal is what led the
prosecution to endeavor to keep that deal secret.” Hayes, 399
F.3d at 987.

   Here, Thomas’s attorney Rex Gay declared in his uncontro-
verted affidavit that the prosecutor agreed with Gay’s assess-
ment that a psychiatric evaluation of Thomas could be
damaging to the State’s case against Silva. The prosecutor
took his concern one step further, concluding that the very
fact of the deal regarding Thomas’s psychiatric evaluation
needed to be concealed from the jury. The State’s deliberate
and strategic decision to make the deal and not to disclose it
suggests the weakness of its post hoc claims that the evidence
was irrelevant.

   The State makes much of the fact that the jury did not find
Silva guilty of Laura Craig’s murder despite having heard
Thomas finger Silva as her killer in exactly the same manner
he implicated Silva in Kevin Thorpe’s death: by relating
Silva’s reaction to a tale told by Shelton. According to the dis-
trict court and the State, the fact that the jury acquitted Silva
on Craig’s murder despite convicting Silva for Thorpe’s mur-
der demonstrates that the jury credited Thomas’s testimony
8634                    SILVA v. BROWN
only where it was corroborated by other evidence. On this
theory, additional impeachment of Thomas would not have
shaken the guilty verdict on Thorpe’s murder because the jury
must have considered Thomas’s story about Thorpe’s death to
have been corroborated more strongly than Thomas’s story
about Craig’s death.

   [12] The problem with this interpretation is that Thomas’s
testimony was the only evidence of Silva’s role in Thorpe’s
murder. Because Thomas’s account of Thorpe’s death is no
more strongly corroborated in the record than Thomas’s claim
that Silva killed Craig, an equally plausible interpretation of
the split verdict is that the jury entertained some doubts about
Thomas’s credibility and so did not believe everything
Thomas told them. If the jury had been presented with evi-
dence of the prosecution’s own doubts as to Thomas’s mental
capacity, the jury might not have believed Thomas’s account
with regard to either murder. Thus the fact that the jury
acquitted Silva of the Craig murder proves little about the
materiality of the secret deal to Silva’s conviction for the
Thorpe murder.

   Finally, the State claims that the undisclosed deal with
Thomas cannot be deemed material under Brady because it
would not have been admissible in court. See Wood v. Bar-
tholomew, 516 U.S. 1, 6 (1995) (per curiam). The State’s
premise is simply incorrect. Whether or not it is true (as the
State claims) that California law would not have allowed
Silva to force a psychiatric evaluation of Thomas and would
have protected as attorney work-product the district attorney’s
doubts about Thomas’s credibility, it is clear that the fact of
the deal itself would have been admissible to impeach
Thomas by calling into question his capacity as a witness and
by illustrating the full extent of the agreement that provided
a motive for Thomas to testify. See Cal. Evid. Code. § 780(c),
(f) (“[T]he court or jury may consider in determining the cred-
ibility of a witness any matter that has any tendency in reason
to prove or disprove the truthfulness of his testimony at the
                          SILVA v. BROWN                     8635
hearing, including . . . [t]he extent of his capacity to perceive,
to recollect, or to communicate any matter about which he
testifies [and] . . . [t]he existence or nonexistence of a bias,
interest, or other motive. . . .”). The State’s admissibility
objection under Wood thus dissolves: the fact of the deal
could have been presented to the jury, and — as our analysis
has demonstrated — this evidence was material in and of
itself.

   [13] In sum, because evidence of the undisclosed deal
could well have undermined the credibility of a vital prosecu-
tion witness, “there is a reasonable probability that, had the
evidence been disclosed to the defense, the result of the pro-
ceeding would have been different.” Kyles, 514 U.S. at 433
(citations and internal quotation marks omitted). Therefore,
the prosecution’s secret deal with Thomas was material to
Silva’s conviction for murder, and the State violated Silva’s
due process rights by failing to disclose the deal to the
defense.

   On appeal, Silva understandably focuses on the effect of
the undisclosed deal on his murder conviction. The strong evi-
dence in the record corroborating the parts of Thomas’s
account relevant to the kidnaping, robbery, and firearms
charges precludes reversal of Silva’s convictions on these
charges.

                    IV.    CONCLUSION

   In our justice system, the prosecuting attorney occupies a
special position of public trust. Courts, citizens, and even
criminal defendants must rely on these public servants to be
honorable advocates both for the community on whose behalf
they litigate and for the justice system of which they are an
integral part. When prosecutors betray their solemn obliga-
tions and abuse the immense power they hold, the fairness of
our entire system of justice is called into doubt and public
confidence in it is undermined.
8636                   SILVA v. BROWN
   The evidence in this case leaves no doubt that Silva was
involved in the sordid conduct that led to the deaths of Kevin
Thorpe and Laura Craig. Unfortunately, the reliability of the
jury’s verdict as to Silva’s role as the triggerman in Thorpe’s
murder was compromised by the Lassen County District
Attorney’s unscrupulous decision to keep secret the deal he
made to prevent an evaluation of the competence of the
State’s star witness. The particularly atrocious nature of the
crimes with which Silva was charged cannot diminish the
prosecutor’s — and our court’s — duty to ensure that all per-
sons accused of crimes receive due process of law.

   [14] We reverse the judgment of the district court and
remand with instructions to grant the writ of habeas corpus
with respect to Silva’s murder conviction, and we reaffirm the
vacation of his sentence in accordance with our disposition in
Silva I, 279 F.3d at 856. We leave Silva’s convictions on the
kidnaping, robbery, and firearms charges undisturbed. The
State shall retry Silva within a reasonable time or resentence
him based on these remaining convictions.

  REVERSED AND REMANDED WITH INSTRUC-
TIONS.
