FOR PUBLICATION
 UNITED STATES COURT OF APPEALS
      FOR THE NINTH CIRCUIT

TIMOTHY CHARLES PARLE,                   No. 06-16780
             Petitioner-Appellee,
              v.                           D.C. No.
                                        CV-01-03487-WHA
DAVID L. RUNNELS, Warden,
                                            OPINION
           Respondent-Appellant.
                                    
       Appeal from the United States District Court
         for the Northern District of California
       William H. Alsup, District Judge, Presiding

                 Argued and Submitted
        June 13, 2007—San Francisco, California

                 Filed October 10, 2007

 Before: Michael Daly Hawkins, A. Wallace Tashima, and
             Carlos T. Bea, Circuit Judges.

               Opinion by Judge Hawkins




                          13677
                     PARLE v. RUNNELS                 13679


                        COUNSEL

Bruce Ortega, Deputy Attorney General for the State of Cali-
fornia, San Francisco, California, for the respondent-
appellant.
13680                   PARLE v. RUNNELS
Martin N. Buchanan, Niddrie, Fish, & Buchanan LLP, San
Diego, California, for the petitioner-appellee.


                           OPINION

HAWKINS, Circuit Judge:

   Domestic violence is a serious problem in America. When
love turns to hate, grave injury—even death—can result.
When that violence spins out of control, considerable prob-
lems confront the criminal justice system. The heat of the
moment and the history of the relationship can make it quite
difficult to assess responsibility. Sometimes it is clear who the
aggressor is or has been; sometimes it is not so clear. The trial
at issue here required a California jury to make just such a dif-
ficult determination. Because we conclude, as did the district
court, that multiple errors in the admission and exclusion of
evidence accumulated to deprive Timothy Charles Parle
(“Parle”) of a constitutionally fair trial, and that the one-sided
prejudice caused by these errors made the state court’s con-
trary conclusion objectively unreasonable, we affirm the grant
of habeas relief.

         FACTS AND PROCEDURAL HISTORY

  Because the relevant facts are recited in this court’s prior
opinion, Parle v. Runnels, 

, 1033-34 (9th Cir.
2004) (Parle I), and the district court’s most recent order,
Parle v. Runnels, 

, 1160-61 (N.D. Cal.
2006) (Parle III), and are largely uncontested by the parties,
we offer only a brief synopsis.

   Parle killed his wife, Mary, on December 17, 1993, by stab-
bing her in the back during a domestic dispute. By all
accounts, Parle and Mary had “a stormy relationship,” punctu-
ated by verbal and physical abuse by both parties. Parle I, 387
                       PARLE v. 

. At trial, Parle conceded that he unlawfully
killed his wife, contesting only his state of mind at the time
of the killing. Although Parle contended that his state of mind
was such that he could be guilty of no more than second-
degree murder or voluntary manslaughter, a jury convicted
him of first-degree murder. See Parle 

.

   On direct review, the California Court of Appeal identified
numerous, serious errors in the trial proceedings. Specifically,
the court of appeal held that the trial court:

    •   Violated Parle’s psychotherapist-patient privilege
        by erroneously holding that the privilege had
        been waived and requiring Parle’s psychiatrist to
        give damaging testimony against Parle;

    •   Improperly excluded rebuttal testimony from a
        defense expert about the effects of a manic epi-
        sode due to severe bipolar disorder, relevant to
        whether Parle had the mental state required for a
        first-degree murder conviction;

    •   Improperly excluded evidence of Mary’s propen-
        sity for violence, including her threats to Parle in
        the weeks leading up to his crime;

    •   Improperly excluded testimony of Parle’s father
        relating to Parle’s appearance and demeanor
        immediately before and after the crime; and

    •   Improperly admitted impermissible character evi-
        dence of Parle’s threats to a police officer five
        years prior to his crime.

Despite these errors, the California Court of Appeal upheld
Parle’s conviction, concluding that the various errors—both
individually and collectively—were harmless. The court of
13682                      PARLE v. RUNNELS
appeal reasoned that the erroneously excluded (or included)
evidence was “essentially cumulative” of other properly
admitted evidence, and therefore that it was not reasonably
probable that the jury would have returned a different verdict
but for the errors.1 People v. Parle, No. H017348, slip op. at
56 (Cal. Ct. App. 2000). As such, the court held that the errors
did not result in a “serious flaw” in Parle’s trial. Accordingly,
“the determinations by the judge and jury were reliable” and
Parle’s trial “fundamentally fair.” 

(internal quota-
tions omitted).

   Parle thereafter sought federal habeas relief. Following
extensive briefing, the district court subsequently granted
relief, concluding that: (1) “the California Court of Appeal
clearly erred in finding that admission of the victim’s diary
did not violate the Confrontation Clause” and (2) “the cumu-
lative effect of this and several other evidentiary errors
deprived petitioner of his due process right to a fair trial.”
This court reversed on appeal, concluding that no Confronta-
tion Clause violation occurred, and remanded for further con-
sideration of Parle’s cumulative error/due process claim.
Parle 

.

   On remand, the district court again granted habeas relief.
The district court concluded: (1) the California Court of
Appeal engaged in an issue-by-issue analysis, rather than a
cumulative effect analysis; and (2) to the extent the state court
actually performed a cumulative error analysis, it applied an
incorrect standard—whether the errors resulted in a “serious
flaw” in defendant’s trial—rather than a “substantial and inju-
rious effect” standard. This court again reversed, concluding
that “[the state] court, however imperfectly, conducted cumu-
lative error review of the trial” and remanding “for the district
court to determine whether the decision was an objectively
  1
    With regard to the constitutional error resulting from Parle’s psychia-
trist’s testimony, the court concluded it was “harmless beyond a reason-
able doubt.” See Chapman v. California, 

, 24 (1967).
                            PARLE v. RUNNELS                           13683
unreasonable application of [clearly established Supreme
Court law]” under AEDPA.2 Parle v. Runnels, No. 05-16610,
177 Fed. Appx. 759, 759 (9th Cir. Apr. 27, 2006) (Parle II).

   Following this second remand, the district court once again
granted habeas relief, concluding that “[t]he erroneous evi-
dentiary rulings . . . infected the trial with such unfairness that
it rose to the level of a due-process violation.” Parle 

. Because “the [cumulative] impact of
these errors is devastating to one’s confidence in the reliabil-
ity of the verdict,” the district court held that the California
Court of Appeal’s “decision to the contrary was an unreason-
able application of [Chambers v. Mississippi, 

(1973), Krulewitch v. United States, 

(1949), and
Hawkins v. United States, 

(1954)].” Parle 

. The State timely appealed.3

      JURISDICTION AND STANDARD OF REVIEW

  We have jurisdiction under 28 U.S.C. §§ 1291 and
2253(c)(3) and “review de novo a district court’s order grant-
ing a writ of habeas corpus.” Parle 

.

   Under AEDPA, habeas relief is available only where a state
court’s rulings “resulted in a decision that was contrary to, or
involved an unreasonable application of, clearly established
federal law, as determined by the [United States] Supreme
Court,” 28 U.S.C. § 2254(d)(1), or were based on “an unrea-
sonable determination of the facts,” 

Where,
as here, the state supreme court denies review of a prisoner’s
habeas petition without comment, we “look to the last rea-
soned state-court decision”: in this case, that of the California
  2
     The Antiterrorism and Effective Death Penalty Act of 1996
(“AEDPA”), 28 U.S.C. §§ 2241 et seq.
   3
     The district court stayed the effectiveness of its order until ninety days
after all appellate proceedings become final. 

v. RUNNELS
Court of Appeal. Van Lynn v. Farmon, 

, 738 (9th
Cir. 2003).

   A state court’s decision involves an unreasonable applica-
tion of clearly established federal law “if ‘the state court iden-
tifies the correct governing legal principle[ ] from [Supreme
Court] decisions, but unreasonably applies that principle to
the facts of the prisoner’s case.’ ”4 Ramirez v. Castro, 365
F.3d 755,762 (9th Cir. 2004) (quoting Williams v. Taylor, 

, 413 (2000)). The state court’s application must be
more than erroneous, it must be “objectively unreasonable.”
Lockyer v. Andrade, 

, 75 (2003). Finally, if a state
court’s decision was objectively unreasonable, we may grant
habeas relief only if the error had a “substantial or injurious
effect” on the verdict. Brecht v. Abrahamson, 

,
637-38 (1993); Parle 

.

                            DISCUSSION

I.       Clearly Established Law

A)       Cumulative Error and Due Process

   [1] The Supreme Court has clearly established that the
combined effect of multiple trial court errors violates due pro-
cess where it renders the resulting criminal trial fundamen-
tally unfair. 

, 302-03 (combined
effect of individual errors “denied [Chambers] a trial in
accord with traditional and fundamental standards of due pro-
cess” and “deprived Chambers of a fair trial”).5 The cumula-
     4
     Our prior holding that the state court performed cumulative error
review, Parle II, 177 Fed. Appx. at 759, operates as law of the case estab-
lishing that the state court’s decision was not “contrary to” clearly estab-
lished Supreme Court law and prevents reconsideration of this issue, see
Murdoch v. Castro, 

, 1067-68 (9th Cir. 2007).
   5
     See also Montana v. Egelhoff, 

, 53 (1996) (stating that
Chambers held that “erroneous evidentiary rulings can, in combination,
                            PARLE v. RUNNELS                          13685
tive effect of multiple errors can violate due process even
where no single error rises to the level of a constitutional vio-
lation or would independently warrant reversal. 

n.3.6

   Under traditional due process principles, cumulative error
warrants habeas relief only where the errors have “so infected
the trial with unfairness as to make the resulting conviction a
denial of due process.” Donnelly v. DeChristoforo, 

, 643 (1974). Such “infection” occurs where the combined
effect of the errors had a “substantial and injurious effect or
influence on the jury’s verdict.” 

(internal quotations omitted); see also 

(noting similarity between Donnelly and Brecht stan-
dards and concluding that “a Donnelly violation necessarily
meets the requirements of Brecht”). In simpler terms, where
the combined effect of individually harmless errors renders a
criminal defense “far less persuasive than it might [otherwise]

rise to the level of a due process violation”); Taylor v. Kentucky, 

, 487 n.15 (1978) (“[T]he cumulative effect of the potentially damag-
ing circumstances of this case violated the due process guarantee of funda-
mental fairness . . . .”).
   Although we have never expressly stated that Chambers clearly estab-
lishes the cumulative error doctrine, we have long recognized the due pro-
cess principles underlying Chambers. See, e.g., Thomas v. Hubbard, 

, 1179-80 (9th Cir. 2002) (analyzing cumulative error in
AEDPA habeas petition); Whelchel v. Washington, 

, 1212
(9th Cir. 2000) (noting that cumulative error doctrine applies on pre-
AEDPA habeas review); United States v. Frederick, 

, 1381
(9th Cir. 1996) (recognizing the importance of considering “the cumula-
tive effect of multiple errors”).
   6
     See also 

(“In analyzing prejudice in a case
in which it is questionable whether any ‘single trial error examined in iso-
lation is sufficiently prejudicial to warrant reversal,’ this court has recog-
nized the importance of considering ‘the cumulative effect of multiple
errors’ and not simply conducting ‘a balkanized, issue-by-issue harmless
error review.’ ”) (quoting 

).
13686                      PARLE v. RUNNELS
have been,” the resulting conviction violates due process. See

, 302-03.

B)    Harmless Error and Cumulative Evidence

   In evaluating a due process challenge based on the cumula-
tive effect of multiple trial errors, a reviewing court must
determine the relative harm caused by the errors. If the evi-
dence of guilt is otherwise overwhelming, the errors are con-
sidered “harmless” and the conviction will generally be
affirmed. See 

(citing United States
v. Berry, 

, 201 (9th Cir. 1980)). The “logical cor-
ollary” of this harmless error doctrine is that trial errors are
more likely to be prejudicial to a defendant—i.e., not
harmless—when the government’s case on a critical element
is weak. 

determining whether the com-
bined effect of multiple errors rendered a criminal defense
“far less persuasive” and had a “substantial and injurious
effect or influence” on the jury’s verdict, the overall strength
of the prosecution’s case must be considered because “a ver-
dict or conclusion only weakly supported by the record is
more likely to have been affected by errors than one with
overwhelming record support.” Strickland v. Washington, 

, 696 (1984).7

   Where a trial court commits an evidentiary error, the error
is not necessarily rendered harmless by the fact there was
other, cumulative evidence properly admitted. See

(holding that, in a close case,
erroneously admitted evidence—even if cumulative of other
evidence—can “tip[ ] the scales” against the defendant); Haw-
  7
     See also Glasser v. United States, 

, 67 (1942) (“[Where]
the scales of justice may be delicately poised between guilt and innocence
. . . error, which under some circumstances would not be ground for rever-
sal, cannot be brushed aside as immaterial since there is a real chance that
it might have provided the slight impetus which swung the scales toward
guilt.”).
                           PARLE v. RUNNELS                         13687

(concluding that erroneously admitted
evidence, “though in part cumulative,” may have “tip[ped] the
scales against petitioner on the close and vital issue of his
[state of mind]”).

C)    Summary

   [2] In sum, the Supreme Court has clearly established that
the combined effect of multiple trial errors may give rise to
a due process violation if it renders a trial fundamentally
unfair, even where each error considered individually would
not require reversal. 

; 

n.3, 298, 302-03. Furthermore, the cumulative
nature of the challenged evidence does not necessarily render
its inclusion (or exclusion) harmless. 

. Rather, the fundamental question in determining
whether the combined effect of trial errors violated a defen-
dant’s due process rights is whether the errors rendered the
criminal defense “far less persuasive,” 

, and thereby had a “substantial and injurious effect or
influence” on the jury’s verdict, 

(internal quotations omitted).

II.   AEDPA Review

A)    Chambers v. Mississippi

   Because Chambers clearly established that the cumulative
effect of trial errors can violate due process, it provides the
starting point for our analysis.8 In light of the district court’s
thorough and accurate account of the Chambers decision, see
Parle 

, we recount its facts
only briefly.
   8
     The State’s argument that Parle’s cumulative error claim is not cogni-
zable on habeas review because it asks the court to recognize a new con-
stitutional rule, see Teague v. Lane, 

(1989), lacks merit. As
noted above, Chambers and its progeny clearly established the cumulative
error doctrine decades ago.
13688                   PARLE v. RUNNELS
   Leon Chambers (“Chambers”) was charged with murder
for allegedly shooting a police officer. Prior to Chambers’s
trial, Gable McDonald (“McDonald”) came forward and pro-
vided a sworn confession that he was the actual shooter.

. However, at a subsequent hear-
ing, McDonald recanted and was released from custody. 

Nonetheless, Chambers’s primary defense at trial was
that McDonald was the real shooter. 

Chambers
called McDonald to the stand and had his out-of-court confes-
sion read to the jury. On cross-examination, however,
McDonald testified that he had repudiated his confession,
explaining that he falsely confessed only after being assured
that he would not go to jail and would share in proceeds from
a tort suit Chambers would bring against the town. 

89, 291. Applying state rules of evidence, the trial court pre-
vented Chambers from treating McDonald as an adverse wit-
ness in order to cross-examine him about his repudiated
confession because McDonald’s testimony had not specifi-
cally implicated Chambers. 

   The trial court also excluded as inadmissible hearsay the
testimony of three witnesses that McDonald had confessed to
them individually that he was the shooter. 

Although Chambers was able to introduce limited testimony
impeaching McDonald’s credibility and supporting his theory
of the case, as a result of the trial court’s rulings, he was pre-
vented from presenting critical evidence to support his claim
that McDonald was the actual shooter, and his primary
defense was therefore “far less persuasive than it might [oth-
erwise] have been.” 

   Chambers appealed the conviction to the Mississippi
Supreme Court, which affirmed. The Supreme Court granted
certiorari, and held that the combined effect of the trial court’s
rulings preventing Chambers from both cross-examining
McDonald and introducing witness testimony of McDonald’s
previous confessions “denied [Chambers] a trial in accord
with traditional and fundamental standards of due process.”
                            PARLE v. RUNNELS                         13689

Notably, the Supreme Court so held even though
the evidence excluded as a result of the trial court’s errors was
at least in part cumulative of other properly admitted evidence9
and the state appellate court had identified no errors of state
law.

B)    Parle’s Case

  In light of the due process principles established in Cham-
bers and the starkly one-sided impact of the errors in Parle’s
case, the California Court of Appeal’s conclusion that the
cumulative effect of the multiple evidentiary errors did not
violate Parle’s due process rights was an objectively unrea-
sonable application of clearly established due process law as
determined by the Supreme Court.10 The district court’s grant
of habeas relief must therefore be affirmed.

   A unique and critical thread runs through the trial errors in
this case: all of the improperly excluded evidence in Parle’s
  9
    For example: (1) McDonald’s sworn, written confession had been read
to the 

; (2) a witness testified that he “saw McDonald
shoot the officer,” 

(3) a second witness testified that “he saw
McDonald immediately after the shooting with a pistol in his hand,” id.;
(4) another witness contradicted McDonald’s account that he had been
having beers in a cafe at the time of the shooting, 

and (5) a gun
dealer testified that McDonald owned a .22-caliber—the same caliber as
the shooter’s—at the time of the crime, 

& n.5.
   10
      The district court held that the California Court of Appeal’s conclu-
sion that the errors were collectively harmless because the evidence at
issue was “essentially cumulative” of other properly admitted evidence
was also an unreasonable application of Supreme Court precedent estab-
lishing that the cumulative nature of evidence does not necessarily render
its erroneous inclusion (or exclusion) harmless. See Parle III, 

at1167-68; see also 

; Haw

. However, because we conclude that the cumulative effect of the
multiple trial errors violated Parle’s due process rights and the California
Court of Appeal’s conclusion to the contrary was an objectively unreason-
able application of clearly established Supreme Court law, we need not—
and do not—examine this additional basis for habeas relief.
13690                       PARLE v. RUNNELS
case—i.e., expert testimony about the effects of a bipolar
manic episode on one’s state of mind, the victim’s previous
threats and history of violence, and Parle’s father’s testimony
about Parle’s appearance and demeanor immediately before
and after the crime—supported Parle’s defense that he lacked
the requisite state of mind for first-degree murder; at the same
time, all of the erroneously admitted evidence—i.e., Parle’s
psychiatrist’s testimony in violation of privilege about Parle’s
minor bipolar disorder and relative stability in treatment, and
evidence of Parle’s violent threats to a police officer—
undermined Parle’s defense and credibility and bolstered the
State’s case. The combined effect of these errors, like those
in Chambers, rendered Parle’s defense “far less persuasive
than it might have been,” 

and therefore had a “sub-
stantial and injurious effect or influence on the jury’s verdict,”

, violating Parle’s due process rights.
And, given the plainly one-sided prejudice resulting from
these errors and their direct relevance to the only contested
issue before the jury, the state court’s conclusion to the con-
trary was objectively unreasonable.

  1)    Erroneous Admission and Exclusion of Medical
        Testimony

   [3] The trial court erroneously admitted damaging testi-
mony from Parle’s psychiatrist, Dr. Antoinette Acenas, in vio-
lation of Parle’s constitutional right to privacy,11 while
simultaneously preventing testimony from Dr. Jay Jackman—
  11
    The right to privacy of a patient’s communications with his psycho-
therapist is grounded in the federal and state constitutions. Caesar v.
Mountanos, 

, 1067-68 (9th Cir. 1976) (recognizing a right
to privacy in psychotherapist-patient relationship arising out of the Four-
teenth Amendment to the U.S. Constitution); San Diego Trolley, Inc. v.
Superior Court, 

, 481 (Cal. Ct. App. 2001) (recog-
nizing right to privacy protected by California Constitution article I, § 1).
This right to privacy exists in addition to the statutory protection of confi-
dential communications between patient and psychotherapist. Cal. Evid.
Code § 1014.
                       PARLE v. RUNNELS                    13691
Parle’s expert medical witness—about the effects of a bipolar
manic episode “relevant to the question whether [Parle] actu-
ally had the mental state required for a first degree murder
conviction.” Parle, No. H017348, slip op. at 31. The cumula-
tive effect of these errors alone violated Parle’s due process
rights and rendered his trial unfair.

  a)   Dr. Acenas

   In her testimony, Dr. Acenas was compelled to reveal
Parle’s private, confidential statements that Mary made him
“ready to explode” and that he had thought of hurting her (and
others), but noted that Parle had never made any specific
complaints about Mary’s violent behavior towards him. Dr.
Acenas further testified that Parle suffered from the more
minor Type II bipolar disorder, characterized by shorter and
less severe mood swings. Finally, she testified that Parle had
not exhibited any manic symptoms around the time of (or in
the 18 months prior to) his crime and generally appeared to
be doing well on his medication. The State seized upon this
testimony in its closing statement, arguing that it bolstered the
State’s theory that Parle had long held violent thoughts about
his wife and possessed the requisite state of mind at the time
of the crime to be convicted of first-degree murder. Despite
the apparent prejudice to Parle from this error, the California
Court of Appeal nonetheless held that the error was “harmless
beyond a reasonable doubt” because the unconstitutionally
admitted testimony “was merely cumulative of other evi-
dence” insofar as “[t]he jury already knew Parle was seeing
a psychiatrist . . . . [and] that he and Mary had been having
marital problems.” People v. Parle, No. H017348, slip op. at
32.

   However, as the district court concluded, the other evidence
of Parle’s medical and marital history “was a far cry from the
force of the medical testimony compelled in violation of the
privilege.” Parle III, 

at 1165. Dr. Acenas’s
testimony was cumulative only in the most general sense that
13692                  PARLE v. RUNNELS
it also discussed Parle’s marriage and general psychological
health. The specificity of the testimony, however, was mir-
rored nowhere else in the record. Moreover, there was no
other specific evidence of Parle’s violent thoughts toward
Mary. Although the record contains evidence of Parle’s vio-
lent tendencies in general, as well as his stormy marriage with
Mary in particular, Dr. Acenas provided the only medical tes-
timony laying the foundation for the State’s theory that
Mary’s murder was premeditated. Furthermore, even if the
evidence were cumulative, this fact does not render its errone-
ous admission necessarily harmless. See 

.

  b)    Dr. Jackman

   The prejudice caused by Dr. Acenas’s erroneously admitted
testimony was exacerbated by the erroneous exclusion of tes-
timony from Dr. Jackman—Parle’s expert psychiatric witness.
Although Dr. Jackman was permitted to testify that Parle suf-
fered from the more severe Type I bipolar disorder and
appeared to be in the midst of a manic episode on the night
of his crime, he was erroneously prevented from testifying
about the effects of a manic episode on one’s general state of
mind and ability to premeditate. Specifically, the trial court
erroneously struck Dr. Jackman’s statements that “bipolar dis-
order is characterized by impulsiveness and poor judgment,
and that a person does not stop to consider the consequences
or alternatives during a manic episode.” Parle III, 448 F.
Supp. 2d at 1165. As the California Court of Appeal held,
Parle was thus erroneously denied the opportunity to present
critical testimony “relevant to the question whether [he] actu-
ally had the mental state required for a first degree murder
conviction.” Parle, No. H017348, slip op. at 31.

   Although this excluded testimony went to the only con-
tested issue at trial and clearly undermined Parle’s defense,
the California Court of Appeal nonetheless concluded that this
error did not violate Parle’s due process rights because he
                       PARLE v. RUNNELS                   13693
“was permitted to present some expert testimony about his
mental disorder,” including Dr. Jackman’s opinion that
“[Parle’s] mental disorder caused him to experience stress,
pressure, irritability, agitation, and mood swings,” and that “a
manic episode may cause a person to become stressed, agi-
tated, and possibly violent.” 

    As the district court noted, however, this alternative evi-
dence “was a thin substitute for the evidence wrongfully
excluded.” Parle III, 

at 1165. The evidence
admitted—that manic episodes may cause a person “to
become stressed, agitated, and possibly violent”—sheds very
little light on whether Parle possessed the requisite state of
mind for first-degree murder, whereas the evidence excluded
—that bipolar disorder is characterized by impulsiveness and
poor judgment, and that a person suffering from a manic epi-
sode does not stop to consider consequences or alternatives—
speaks directly to the only relevant issue: premeditation.

   The prejudicial effect of the erroneous exclusion of Dr.
Jackman’s testimony was made worse during closing argu-
ments: Parle’s counsel was specifically prevented from argu-
ing the effects of a manic episode on deliberation. During his
closing argument, Parle’s counsel argued that Parle was suf-
fering from a manic episode at the time of the murder and “he
was less likely to carefully consider his actions and less able
to deal with the antagonism that was inherent in the relation-
ship, apt to be more rash, more impulsive as a result of this
disorder, less able to exercise good judgment.” The prosecutor
objected, moving the court to instruct the jury there was no
evidence to support “the last two or three assertions.” The
objection was sustained, and the court instructed that
“[a]rguments of counsel, whether it be the prosecution or the
defense, are merely argument and not evidence.”

  The prosecution, however, was permitted to attack Parle’s
defense and opine that “[t]he evidence is that bipolar disorder
has not been testified to as diminishing a person’s ability to
13694                      PARLE v. RUNNELS
premeditate or deliberate at all.” Parle III, 

at 1166.

  c)    Cumulative Effect of Errors / Cumulative Nature of
        Evidence

   [4] Taken together, the wrongful admission of Dr. Acenas’s
testimony and the erroneous exclusion of portions of Dr. Jack-
man’s left the jury with only half the picture. It had reliable
testimony from Parle’s own psychiatrist about Parle’s relative
good mental health prior to the crime, as well as his history
of violent tendencies and hatred for his wife—all supporting
the prosecution’s argument for premeditation—but lacked
critical evidence of whether Parle formed the requisite mental
state in the midst of a manic episode caused by severe bipolar
disorder, which clearly would have bolstered his defense. The
cumulative effect of these two errors alone rendered Parle’s
defense “far less persuasive than it might have been” and
would have had a “substantial and injurious effect or influ-
ence” on the jury’s verdict.12

  Like the evidence excluded in Chambers, this wrongfully
admitted and excluded evidence went to the heart of the cen-
  12
    The State discounts the import of this medical testimony, noting the
“overwhelming nature of all of the properly-admitted evidence establish-
ing that [Parle] premeditated and deliberated the killing of his wife.”
State’s Br. at 35. However, as discussed above, although the record con-
tained other evidence establishing Parle’s violent tendencies, no other evi-
dence so directly pertained to his mental state at the time of the crime.
   Furthermore, the State’s reliance on this court’s prior holding that the
record contained “overwhelming evidence” of Parle’s intent misses the
mark. See Parle 

. There is no question that Parle
intended to kill his wife; the only issue before the California Court of
Appeal was his state of mind at the time of this intentional killing, i.e.,
whether the killing was intentional and deliberated (first degree murder)
or intentional but not deliberated (second degree murder). This court’s
prior decision is silent as to the strength of the State’s evidence on this
question.
                       PARLE v. RUNNELS                    13695
tral issue in the case. In Chambers, the excluded evidence per-
tained to the identity of the shooter—Chambers’s primary
defense—while, here, the erroneously admitted and excluded
evidence pertained to the only relevant issue (and Parle’s only
defense): Parle’s state of mind at the time of the crime. Fur-
thermore, even if—as the California Court of Appeal
concluded—the evidence in question was “cumulative” of
other properly admitted evidence, the errors may nonetheless
have tipped the scales against Parle and rendered his trial fun-
damentally unfair. See 

.
Indeed, as discussed above, the erroneously excluded evi-
dence in Chambers was also largely cumulative of other evi-
dence properly before the jury, yet the Supreme Court had no
difficulty concluding that the combined effect of the trial
errors required reversal. See supra note 9; see also Parle III,

at 1167 (discussing cumulative nature of evi-
dence in Chambers).

   [5] In sum, the cumulative effect of the erroneous inclusion
of Dr. Acenas’s testimony and wrongful exclusion of portions
of Dr. Jackman’s testimony rendered Parle’s defense “far less
persuasive,” infecting his trial with unfairness, and depriving
him of due process. See 

; Don-

. Furthermore, in view of the unique
symmetry of these errors—by which each so starkly amplified
the prejudice caused by the other—and their direct relation to
the sole issue contested at trial, the California Court of
Appeal’s conclusion to the contrary was objectively unreason-
able, and Parle is entitled to habeas relief.

  2)   Additional Errors

   [6] The trial court’s errors did not end with the medical tes-
timony. Rather, the prejudicial impact of those errors was
exacerbated by the trial court’s additional errors in excluding
evidence of Mary’s previous threats and character for vio-
lence and admitting evidence of Parle’s previous violent
threats against a police officer. Viewed collectively with the
13696                  PARLE v. RUNNELS
medical testimony errors, these errors undeniably rendered
Parle’s defense “far less persuasive than it might have been”
and thereby violated his due process rights.

  a)    Mary’s Character for Violence and Threats Against
        Parle

   The trial court also erred in excluding evidence pertaining
to Mary’s character for violence and threats against Parle.
First, the trial court erred in preventing Mary’s nurse from
testifying that, thirteen days prior to the crime, Mary
expressed “vindictiveness” toward Parle and had stated that
she’d “like to hurt him” and “want[ed] to kill him.” Second,
the trial court erroneously excluded as hearsay Parle’s testi-
mony about Mary’s various threats against him, including her
threat—four days before Parle’s crime—to kill him and their
son.

   Once again, the California Court of Appeal held that the
exclusion of this evidence, though erroneous, was harmless
because it “was essentially cumulative of other evidence.” 

As Chambers and Krulewitch make clear, just because
evidence is cumulative does not necessarily render its wrong-
ful exclusion harmless. Though true the record contained evi-
dence of Mary’s history of violence toward Parle, the
excluded testimony provided the only evidence of Mary’s
threats to kill Parle in the days leading up to his crime. Fur-
thermore, the bulk of the admitted testimony regarding
Mary’s character came from “interested witnesses”—i.e.,
Parle and his father—whereas the testimony of Mary’s nurse
would have provided unbiased and seemingly reliable corrob-
oration of the other evidence of Mary’s violent tendencies
toward Parle.

  b)    Parle’s Threats Against a Police Officer

  Finally, the trial court also erred in admitting impermissible
character evidence of Parle’s threats to a police officer five
                       PARLE v. RUNNELS                   13697
years prior to his crime, but concluded that the error was
harmless in light of other evidence of Parle’s character for
threatening violence. The inclusion of this evidence, espe-
cially when coupled with the exclusion of certain evidence
concerning Mary’s violent tendencies and threats against
Parle, once again painted an incomplete picture for the jury:
The evidence depicted Parle as an extremely violent individ-
ual based on five-year-old allegations, yet neglected to dem-
onstrate that Mary had threatened to kill Parle only days
before. Given that the sole issue before the jury was Parle’s
state of mind at the time of the crime, this unbalanced presen-
tation necessarily undermined Parle’s defense.

                       CONCLUSION

   [7] Because all of the trial court’s errors pertained to evi-
dence relevant to the only issue before the jury—Parle’s state
of mind at the time of the crime—and all of the improperly
admitted evidence bolstered the State’s case, while all of the
erroneously excluded evidence rendered Parle’s defense far
less persuasive than it might have been, it was objectively
unreasonable for the California Court of Appeal to conclude
that the combined effect of these errors did not violate Parle’s
due process rights. That the evidence in question may have
been partially cumulative of other properly admitted evidence
does not render the errors necessarily harmless because the
State’s case establishing Parle’s premeditation was less than
overwhelming, and the jury’s verdict is therefore more likely
to have been affected by the trial court’s errors. See Strick-

; 

; see
also 

.

   As in Chambers, the seminal cumulative error case, the
errors in Parle’s trial went to the heart of the defense’s case
and the only issue before the jury. The combined effect of the
trial court’s multiple errors rendered Parle’s defense “far less
persuasive than it might have been,” 

, resulting in a “substantial and injurious effect or influ-
13698                       PARLE v. RUNNELS
ence” on the jury’s verdict, 

, which
“so infected the trial with unfairness as to make the resulting
conviction a denial of due process,” 

. Further, under the unique and unfortunate circumstances
of this case, the California Court of Appeal’s contrary conclu-
sion was an objectively unreasonable application of clearly
established federal due process law, as set forth in Chambers,
Donnelly, and Brecht.13

   In so holding, like the Chambers Court itself, “we establish
no new principles of constitutional 

.
“Rather, we hold quite simply that under the facts and circum-
stances of this case the rulings of the trial court deprived
[Parle] of a fair trial,” 

and the California Court
of Appeal’s decision to the contrary was objectively unrea-
sonable because, in light of the one-sided impact of the multi-
ple errors, “the[ir] collective presence . . . is devastating to
one’s confidence in the reliability of this verdict.” Killian v.
Poole, 

, 1211 (9th Cir. 2002).

  For the foregoing reasons, the district court’s order granting
Parle’s habeas petition is AFFIRMED.




  13
     Cf. 

(combined effect of errors resulting
in: (1) the admission of evidence establishing motive and access to murder
weapon, (2) the admission of evidence of prior weapon use, (3) violation
of defendant’s right to confront a key witness, and (4) the exclusion of evi-
dence of an alternative perpetrator violated due process, and the “[state
court’s] contrary conclusion [constituted] an unreasonable application of
Donnelly’s well-established principles of due process law”).