PUBLISHED

UNITED STATES COURT OF APPEALS
               FOR THE FOURTH CIRCUIT


JAMES NEIL TUCKER, SR.,               
              Petitioner-Appellant,
                v.
JON E. OZMINT, Director, South
Carolina Department of Corrections;              No. 03-5
HENRY DARGAN MCMASTER,
Attorney General, State of South
Carolina,
            Respondents-Appellees.
                                      
           Appeal from the United States District Court
         for the District of South Carolina, at Charleston.
               Patrick Michael Duffy, District Judge.
                       (CA-02-1110-2-23AJ)

                     Argued: September 24, 2003

                     Decided: December 1, 2003

     Before MICHAEL, MOTZ, and SHEDD, Circuit Judges.



Affirmed by published opinion. Judge Shedd wrote the opinion, in
which Judge Michael and Judge Motz joined.


                            COUNSEL

ARGUED: Robert Edward Lominack, CENTER FOR CAPITAL
LITIGATION, Columbia, South Carolina, for Appellant. Donald John
Zelenka, Assistant Deputy Attorney General, Columbia, South Caro-
2                          TUCKER v. OZMINT
lina, for Appellees. ON BRIEF: Teresa L. Norris, CENTER FOR
CAPITAL LITIGATION, Columbia, South Carolina; Thomas R.
Haggard, Ridgeway, South Carolina, for Appellant. Henry Dargan
McMaster, Attorney General, John W. McIntosh, Chief Deputy Attor-
ney General, Columbia, South Carolina, for Appellees.


                              OPINION

SHEDD, Circuit Judge:

   James Neil Tucker was convicted by a South Carolina jury of the
murder of Rosa Lee "Dolly" Oakley. Upon the jury’s recommenda-
tion, the trial court sentenced Tucker to death. After his direct appeal
and post-conviction review yielded no relief in the state courts,
Tucker filed a petition for writ of habeas corpus in federal district
court. The district court dismissed the petition. On appeal, Tucker
claims that he was denied his Sixth Amendment right to effective
assistance of counsel because his trial counsel (1) failed to provide the
defense expert two documents relating to Tucker’s childhood sexual
abuse and (2) failed to discover that one of the State’s three experts
was subject to professional discipline at the time of trial. We issued
a certificate of appealability on both of these claims. After further
review, we find no error in the denial of habeas relief, and we affirm
the judgment of the district court.

                                   I.

   Dolly Oakley was in her yard at her Sumter County, South Caro-
lina residence when Tucker pulled into her driveway on June 25, 1992.1
Tucker pulled out a gun and forced Oakley into the house and then
into her bedroom. Just as Tucker was preparing to bind Oakley with
tape, Joe Black rang the doorbell. Black and James Howard (who
waited outside in the car) were looking for Oakley’s husband. Both
    1
   This recitation of the facts underlying Tucker’s convictions is taken
from the findings contained in the Supreme Court of South Carolina’s
opinion disposing of Tucker’s direct appeal. See State v. Tucker, 

(S.C. 1996).
                           TUCKER v. OZMINT                            3
Tucker and Oakley went out into the driveway as Black was leaving
the house. Oakley began screaming, "Don’t leave me, he’s going to
kill me," holding Black’s arm as he sat in Howard’s car. Howard pan-
icked and drove away. Tucker dragged Oakley back into the house,
took fourteen dollars from her purse, and shot her twice in the head
at close range. Tucker testified that he shot her the first time when she
tried to grab the gun. He shot her a second time to "put her out of her
misery."

   Tucker’s crime spree did not end with the murder of Dolly Oakley.
Still in Sumter County, he broke into the Christian Fellowship Church
and later the mobile home of Kenneth Parker. Tucker moved on to
neighboring Calhoun County, where he murdered another woman,
Shannon Mellon, and stole her car. Tucker then drove north, aban-
doned the car, and crossed the state line into North Carolina. Tucker
was finally captured in Maggie Valley, North Carolina on July 10,
1992. Once in custody, Tucker confessed to the murders of both Oak-
ley and Mellon.

   Tucker was first tried in Calhoun County for the murder of Shan-
non Mellon. That jury convicted Tucker of murder, armed robbery,
first-degree burglary, and grand larceny of a vehicle. Tucker was sen-
tenced to death. The Supreme Court of South Carolina affirmed the
convictions but reversed the death sentence. State v. Tucker, 

(S.C. 1995). At a subsequent sentencing hearing, Tucker
again received a death sentence, which the Supreme Court of South
Carolina later affirmed. State v. Tucker, 

(S.C. 1999).

   The jury in this case found Tucker guilty of murder, kidnapping,
first-degree burglary, armed robbery, and possession of a weapon dur-
ing a violent crime for his actions at the Oakley residence. The jury
also found Tucker guilty of third-degree burglary for the break-in at
Christian Fellowship Church. Finally, the jury convicted Tucker of
first-degree burglary and larceny for the break-in at Parker’s mobile
home.

   At sentencing, Tucker’s counsel argued that Tucker should not
receive a death sentence because he suffered from an antisocial per-
sonality disorder stemming from horrific physical and sexual abuse.
Dr. Robert Noelker, an expert in forensic psychology retained by the
4                          TUCKER v. OZMINT
defense, testified that Tucker had suffered from "sustained, pro-
longed, [and] severe" abuse as a child — physical abuse from his
step-father and sexual abuse from his older step-brother. As a result
of this abuse, Tucker "was taught that aggression was a way of getting
things, being assertive, being aggressive, being violent was a way of
getting something." In sum, Dr. Noelker concluded that Tucker
understood the requirements of the law but lacked the ability to con-
form his behavior to those standards. "That inability to conform," in
Dr. Noelker’s opinion, was "a result of [Tucker’s] life’s total experi-
ences, but more specifically as a result of his antisocial personality
disorder."

   The State countered Tucker’s mitigation case with three expert wit-
nesses who testified that antisocial personality disorder is merely a
description of behavior, not a mental disease or defect that caused
Tucker to murder Oakley. Forensic psychiatrist Dr. Richard Frierson
diagnosed Tucker as having antisocial personality disorder, but he
explained that "[a]ntisocial personality disorder does not affect a per-
son’s ability to choose [his] behavior. . . . The disorder does not cause
criminal behavior." Likewise, Dr. Steven Shea, a clinical psycholo-
gist, testified that Tucker "has an antisocial personality disorder" but
that the disorder "does not preclude [him] from choosing whether or
not to act." According to Dr. Shea, "[t]he personality disorders are a
way of describing people who have a certain tendency to act a certain
way. It’s not a mental disease in the sense that it’s a — a brain dis-
ease." Finally, Dr. John Dunlap agreed with the State’s other experts
that antisocial personality disorder is descriptive, not causative: "Ac-
tually the diagnosis of antisocial personality is primarily a description
of behavior that you have. It’s not the reason you have the behaviors."

   The trial court instructed the jury that it could consider four statu-
tory aggravating factors and four statutory mitigating factors. See S.C.
Code Ann. § 16-3-20(C)(a)-(b). In particular, the jury was instructed
that it could consider as mitigating circumstances Tucker’s mental or
emotional disturbance, whether he acted under duress, any mental
incapacity, and his age or mentality at the time of the crime. See 

(5)-(7). At defense counsel’s request, the trial
court submitted the following non-statutory mitigation factors for
consideration as well: (1) cooperation with law enforcement officials,
(2) circumstances surrounding Tucker’s childhood, (3) circumstances
                           TUCKER v. OZMINT                             5
surrounding Tucker’s experience in prison, (4) any non-statutory miti-
gating circumstances, and (5) any mitigating circumstances supported
by the evidence.

   The jury found the existence of three statutory aggravating factors
and recommended a death sentence. The trial court then sentenced
Tucker to death for the murder of Dolly Oakley, life imprisonment for
kidnapping, life imprisonment for first-degree burglary, twenty-five
years for armed robbery, five years for possession of a weapon, five
years for third-degree burglary, and thirty days for larceny.

   The Supreme Court of South Carolina affirmed the convictions and
the sentence, State v. Tucker, 

(S.C. 1996), and the
Supreme Court of the United States denied certiorari, Tucker v. South
Carolina, 

(1997). Tucker then filed an application for
post-conviction relief ("PCR") in state court; after conducting an evi-
dentiary hearing, the PCR court denied relief on the merits of Tuck-
er’s claims. The Supreme Court of South Carolina denied certiorari,
as did the Supreme Court of the United States, Tucker v. Maynard,

(2002). Tucker then filed a petition for writ of habeas
corpus in the district court pursuant to 28 U.S.C. § 2254. Upon a rec-
ommendation from the magistrate judge, the district court denied
relief on the merits of Tucker’s claims. This appeal followed.

                                   II.

   We review de novo the district court’s denial of habeas relief based
on a state court record. Bell v. Ozmint, 

, 233 (4th Cir.
2003). Where a state court resolved the merits of a claim for post-
conviction relief, federal habeas relief is not available unless the state
court’s decision was "contrary to, or involved an unreasonable appli-
cation of, clearly established Federal law, as determined by the
Supreme Court of the United States," or was "based on an unreason-
able determination of the facts in light of the evidence presented in
the State court proceeding." 28 U.S.C. § 2254(d).

   The "contrary to" and "unreasonable application" clauses of
§ 2254(d) have independent meanings. Bell v. Cone, 

,
694 (2002). Relief is available under the "contrary to" clause "if the
state court applies a rule different from the governing law set forth in
6                           TUCKER v. OZMINT
[Supreme Court] cases, or if it decides a case differently than [the
Supreme Court has] done on a set of materially indistinguishable
facts." 

is available under the "unreasonable
application" clause "if the state court correctly identifies the govern-
ing legal principles from [Supreme Court] decisions but unreasonably
applies it to the facts of the particular case." 

of this
inquiry is "whether the state court’s application of clearly established
federal law is objectively unreasonable," not whether it is merely
incorrect. 

Williams v. Taylor, 

, 409-10
(2000) (stating that habeas relief is not warranted under the "unrea-
sonable application" clause "simply because the court concludes in its
independent judgment that the relevant state-court decision applied
clearly established federal law erroneously or incorrectly").

   To the extent that Tucker challenges certain factual findings made
by the state court, federal habeas relief is available only if the state
court’s decision to deny post-conviction relief was "based on an
unreasonable determination of the facts." 28 U.S.C. § 2254(d)(2). In
reviewing a state court’s ruling on post-conviction relief, we are
mindful that "a determination on a factual issue made by a State court
shall be presumed correct," and the burden is on the petitioner to rebut
this presumption "by clear and convincing evidence." 

   Tucker contends that he was denied his Sixth Amendment right to
assistance of counsel during his capital sentencing proceedings. Sixth
Amendment ineffective assistance of counsel claims are governed by
the familiar standards of Strickland v. Washington, 

(1984).2 In order to prevail on an ineffective assistance claim, the
petitioner must prove that (1) counsel’s performance was deficient
and (2) the deficient performance actually prejudiced the defense. 

    2
    The state court properly identified Strickland as the governing legal
rule, so Tucker could not obtain habeas relief under the "contrary to"
clause of § 2254(d). The question presented in this appeal is whether the
state court’s application of Strickland to the particular facts of this case
was objectively unreasonable. See 

.
                          TUCKER v. OZMINT                            7
   Counsel’s performance is deficient only if it falls "below an objec-
tive standard of reasonableness." 

The Supreme Court has
cautioned that "[i]t is all too tempting for a defendant to second-guess
counsel’s assistance after conviction or adverse sentence, and it is all
too easy for a court, examining counsel’s defense after it has proved
unsuccessful, to conclude that a particular act or omission of counsel
was unreasonable." 

Thus, in reviewing counsel’s perfor-
mance at trial, "a court must indulge a strong presumption that coun-
sel’s conduct falls within the wide range of reasonable professional
assistance." 

is prejudicial only if "there is a reasonable
probability that, but for counsel’s unprofessional errors, the result of
the proceeding would have been different. A reasonable probability
is a probability sufficient to undermine confidence in the outcome" of
the proceeding. 

. Where the petitioner
challenges a death sentence, "the question is whether there is a rea-
sonable probability that, absent the errors, the sentencer . . . would
have concluded that the balance of aggravating and mitigating cir-
cumstances did not warrant death." 

In making this determi-
nation, a reviewing court should consider the totality of the evidence
presented to the factfinder. 

claims that his trial counsel were constitutionally inade-
quate because they failed to provide to Dr. Noelker two reports relat-
ing to Tucker’s childhood sexual abuse. These records were produced
by Utah authorities in connection with Tucker’s juvenile detention in
the 1970s. The first report, a document prepared by Floyd Bradshaw
in 1970 (the "Bradshaw report"), stated that Tucker

    admits to homosexual activity with both Wayne (brother)
    and Randy (half-brother). He has watched them engage in
    various types of homosexual activity with each other. . . . He
    says the brothers are queers. He thinks something is wrong
    with him also. He feels extremely guilty about what he has
    done. He expresses a need to be locked up in detention for
    awhile. He has said on a couple of occasions that it really
    doesn’t matter what happens to him in [c]ourt.
8                          TUCKER v. OZMINT
The second report, prepared by James Marchel in 1972 (the "Marchel
report"), described Tucker’s inability to get along with his stepfather:

    He feels that the relationship between himself and his step-
    father is beyond repair. If given his choice, he would choose
    any institution rather than go home.

       Although [Tucker’s] background and development
    reflect[] a great deal of miss-directed [sic] and frightening
    sexual activity and experience, this does not appear to be the
    primary motivating factor for his present behavior. Rather,
    all of [Tucker’s] delinquent behavior, including his sexual
    behavior, seems more to be a way of insuring that he will
    not be required to return to his home.

       . . . He is unable to relate to his [step]father, and so is con-
    stantly at odds with him. They frequently argue, and often
    do not speak to each other for several days at a time.

   Tucker asserts that his counsel unreasonably limited the scope of
their investigation into his childhood abuse, failing to provide these
Utah records to Dr. Noelker as proof that Tucker reported physical
and sexual abuse as early as 1970. Counsel’s failure to investigate
potential defenses or mitigating circumstances may amount to ineffec-
tive assistance. Wiggins v. Smith, ___ U.S. ___, 

, 2535
(2003); Byram v. Ozmint, 

, 209 (4th Cir. 2003). As the
Supreme Court has noted, however, "Strickland does not require
counsel to investigate every conceivable line of mitigating evidence
no matter how unlikely the effort would be to assist the defendant at
sentencing." 

. In the end, "a particular
decision not to investigate must be directly assessed for reasonable-
ness in all the circumstances, applying a heavy measure of deference
to counsel’s judgments." 

   The petitioner in Wiggins claimed that his trial counsel were inef-
fective for failing to obtain a social history that would have revealed
childhood sexual abuse. 

In preparing their mitigation
case, counsel relied upon (1) reports of psychological tests that
revealed nothing about the Wiggins’s social history, (2) a presentence
investigation that included a one-page account of Wiggins’s "personal
                            TUCKER v. OZMINT                             9
history," and (3) Department of Social Services records documenting
Wiggins’s placements in foster care. 

Despite the fact that
the Department of Social Services record indicated significant prob-
lems in Wiggins’s family life, his counsel "put on a halfhearted miti-
gation case" that made no mention of Wiggins’s family background.

As a result, only one significant mitigating factor —
Wiggins’s lack of a criminal history — went to the jury. 

Especially in light of the fact that the public defender made funds
available for counsel to retain a forensic social worker, the Supreme
Court held that counsel’s failure to expand their investigation fell
short of prevailing professional standards. 

   Tucker’s counsel, by contrast, presented a substantial mitigation
case at sentencing. They presented five witnesses, including Tucker’s
wife, two vocational rehabilitation workers who knew Tucker, a
widow whose husband Tucker had befriended while in prison, and Dr.
Noelker, a clinical psychologist qualified as an expert in forensic psy-
chology. Dr. Noelker described at length Tucker’s history of abuse as
a child and its connection to Tucker’s antisocial personality disorder.
Dr. Noelker testified that in preparation for his testimony, he (1) inter-
viewed Tucker on four different occasions, (2) read the voluntary
statement made by Tucker in this case, (3) reviewed the deposition of
the doctor who testified in Tucker’s Calhoun County trial, and (4)
reviewed a social history prepared by a licensed social worker in
advance of the Calhoun County trial.3 Relying upon these sources, in
addition to his twenty-four years’ experience as a clinical psycholo-
gist, Dr. Noelker told the jury that Tucker had a conduct disorder as
a juvenile and more recently was diagnosed with antisocial personal-
ity disorder.

  According to Dr. Noelker, Tucker’s personality disorder was likely
caused by "early sexual and/or physical abuse, early and sustained
parental indifference and/or the lack of concern or care, the lack of
  3
   Trial counsel testified that they made a calculated decision not to call
the social worker as a witness based on her performance as a witness in
the Calhoun County trial. Nevertheless, counsel did believe that the
social history she prepared was complete and accurate. Tucker has not
directly challenged counsel’s decision not to call the social worker as a
witness, nor would such a challenge succeed under Strickland.
10                          TUCKER v. OZMINT
a solid role model as a parent." Dr. Noelker testified, Tucker, at only
eighteen months of age, was found abandoned in a locked car with a
broken leg; that his parents fled the state in order to avoid prosecu-
tion; and that Tucker was the target of sexual and physical abuse from
family members until he was about eleven years old. As a result of
this abuse, Dr. Noelker testified that Tucker was unable to conform
his behavior to common standards. The record leaves no doubt that
the jury was offered a clear, coherent mitigation case that focused on
Tucker’s history of abuse.

   Counsel’s performance in preparing Tucker’s mitigation case far
surpassed the inadequate performance described in Wiggins.4 Counsel
attended the previous trial, made reasoned judgments about which
witnesses to call, and presented an expert psychologist who gave the
jury a full picture of Tucker’s disturbing social history. "Although
counsel should conduct a reasonable investigation into potential
defenses, Strickland does not impose a constitutional requirement that
counsel uncover every scrap of evidence that could conceivably help
their client." Green v. French, 

, 892 (4th Cir. 1998),
abrogated on other grounds by Williams v. Taylor, 

(2000). See also 

(holding that trial counsel
were not ineffective for failing to obtain adoption records that would
have provided additional proof that the petitioner suffered from fetal
alcohol syndrome). In this case, trial counsel reasonably investigated
  4
    Counsel’s performance also surpassed the inadequate performance
described in Bloom v. Calderon, 

(9th Cir. 1997), upon
which Tucker relies. Counsel in Bloom "did practically nothing" to pre-
pare the defense expert for his examination of the petitioner. 

Counsel never spoke to the expert before his interview with the peti-
tioner, nor did he provide the expert with documents that the expert affir-
matively requested. 

After a quick look at the few documents
provided by counsel and an interview with the petitioner, the defense
expert prepared a report that the Ninth Circuit described as "devastating"
to the petitioner. 

subsequent interview with the petitioner, the
expert revised his opinion 

. On direct
examination, counsel simply ignored the first report and made no attempt
to minimize its certain impact on cross-examination. 

—
suggesting a near-total absence of assistance of counsel — bear no
resemblance to the facts of this case. Tucker’s reliance upon Bloom is
altogether misplaced.
                          TUCKER v. OZMINT                           11
Tucker’s history of abuse and presented a thorough mitigation case at
sentencing. We conclude, therefore, that the state court’s decision was
not an unreasonable application of Strickland’s performance require-
ment.

  Even if counsel’s performance was unreasonable, their error did
not result in prejudice. In determining whether counsel’s allegedly
unreasonable performance resulted in prejudice to Tucker’s sentence,
we "reweigh the evidence in aggravation against the totality of avail-
able mitigating evidence." 

. A finding of
prejudice is appropriate only if the facts "undermine confidence in the
outcome" of the proceeding, in this case a death sentence. 

.

   The State offered substantial evidence of aggravating circum-
stances. Specifically, the State proved three statutory aggravating fac-
tors — kidnapping, burglary, and armed robbery at the Oakley
residence. The jury also heard evidence of the crime spree that fol-
lowed as Tucker fled Sumter County, his murder of Shannon Mellon
in Calhoun County, a series of burglaries and other property crimes,
and his ultimate capture. The jury also heard testimony describing
Tucker’s past violent crimes.

    As the centerpiece of Tucker’s case in mitigation, Dr. Noelker tes-
tified that Tucker suffered from antisocial personality disorder stem-
ming from childhood physical and sexual abuse. According to Dr.
Noelker, Tucker "was — was and is — a severely, if not profound-
ly[,] physically and sexually abused child and he carries those charac-
teristics with him into adulthood." After recounting specific episodes
of abuse from Tucker’s childhood, Dr. Noelker testified that he was
"convinced" and it was his "professional opinion" that Tucker was
"both physically and sexually abused" from an early age. The result
of this abuse, said Dr. Noelker, was an antisocial personality disorder
that rendered Tucker unable to conform his behavior to common stan-
dards.

   Tucker now argues that his mitigation case would have been
stronger had Dr. Noelker been able to refute the State’s cross-
examination with the Utah juvenile records. On cross-examination,
the solicitor suggested that Tucker had fabricated his claims of child-
12                         TUCKER v. OZMINT
hood abuse in order to avoid a death sentence. Tucker asserts that the
Utah juvenile records would have proved that he reported abuse as
early as 1970.

   We doubt that the result of the sentencing proceeding turned on the
adequacy of Dr. Noelker’s response to the solicitor’s argument. In
fact, all of the expert witnesses — even the State’s experts — agreed
that Tucker had been abused as a child. One of the State’s experts, Dr.
Steven Shea, testified that he personally believed Tucker was abused
as a child, sometimes severely. Given this uniform evidence of abuse,
we do not think it likely that the solicitor’s argument suggesting fabri-
cation significantly undermined Tucker’s mitigation case.

   Moreover, it is not at all clear that the Utah juvenile records would
have answered the solicitor’s charge of fabrication. Indeed, the most
those records showed was that Tucker told authorities — again in the
context of criminal proceedings — that he had a troubled relationship
with his father and that he had previously engaged in disturbing, even
"frightening," sexual conduct with his step-brother. These records do
not reflect contemporaneous reports of abuse by Tucker. And that was
the solicitor’s point: No one ever lodged a complaint against Tucker’s
step-father or step-brother at the times when the abuse was alleged to
have occurred, and no one other than Tucker himself ever reported
such abuse before this trial.5 Thus, it is altogether possible — indeed
likely — that the solicitor would have maintained his charge of fabri-
cation even if Dr. Noelker had made reference to the Utah juvenile
records.

   Finally, Dr. Noelker answered the solicitor’s cross-examination by
stating unequivocally that his conclusions were not affected by the
timing of Tucker’s allegations of abuse. Based on his review of other
records (including the social history prepared for the Calhoun County
trial) and his own interviews with Tucker, Dr. Noelker believed that
Tucker had been subject to physical and sexual abuse during his
childhood. This abuse, according to Dr. Noelker, resulted in the
  5
   Tucker’s trial counsel apparently understood this to be the substance
of the solicitor’s argument when he stipulated that the family never
reported to law enforcement authorities what one brother had done to the
other.
                           TUCKER v. OZMINT                            13
development of a personality disorder, which caused Tucker to
engage in aggressive and violent behaviors. Even after reviewing the
Utah juvenile records, Dr. Noelker stated that he had not seen "any
substantial differences" that would cause him to change his conclu-
sions.

   On balance, there is no reason to lack confidence as to the outcome
in this case because the aggravating circumstances submitted to the
jury outweighed the mitigating circumstances. Tucker’s best case was
that he suffered from an antisocial personality disorder caused by ter-
rible physical and sexual abuse as a child. Dr. Noelker made this case,
but the State’s experts uniformly testified that antisocial personality
disorder is merely descriptive and does not explain the cause for
Tucker’s criminal behavior. Dr. Noelker’s opinion was unaffected by
the two Utah juvenile records, and we doubt that his mentioning those
records in response to the State’s cross-examination would have bol-
stered Tucker’s mitigation case in any significant sense. The state
court’s application of Strickland’s prejudice requirement was not
unreasonable, and the district court properly denied habeas relief on
this claim.6
  6
    Tucker contends that some of the state court’s factual findings were
unreasonable in light of the record evidence. Specifically, Tucker takes
issue with the following factual findings made by the PCR court: (1)
Tucker "expressed a desire that counsel not make an issue of any sexual
abuse," (2) trial counsel determined that "there really were not many
family members or friends who were helpful in the defense’s pretrial
preparation," and (3) the Utah documents did not indicate that Tucker
was sexually abused but "merely reflect that he engaged in homosexual
activity, and that he felt guilty about it." We need not determine whether
these findings were unreasonable, since they are not necessary to reach
the conclusion that Tucker’s counsel acted reasonably in their investiga-
tion and presentation of Tucker’s childhood abuse. Accordingly, Tucker
is not entitled to relief under 28 U.S.C. § 2254(d)(2), which authorizes
relief only where the state court’s decision was "based on" an unreason-
able determination of the facts.
   Tucker also takes issue with the PCR court’s reliance upon his state-
ment to the jury that there was no excuse for his conduct. The Supreme
Court of South Carolina agreed with Tucker on this point, citing Johnson
v. Catoe, 

(S.C. 1999), but nevertheless affirmed the PCR
court’s conclusion that Tucker could not demonstrate prejudice. In accor-
dance with the Supreme Court of South Carolina’s ruling, we have given
no weight to the PCR court’s reliance upon Tucker’s closing statement.
14                         TUCKER v. OZMINT
                                   B.

   Tucker also contends that his counsel were ineffective for failing
to investigate and challenge the qualifications of Dr. John Dunlap,
one of the State’s three expert witnesses. Post-conviction counsel
learned that Dunlap was on probation from the practice of medicine
at the time of Tucker’s trial, and Tucker now claims that his trial
counsel should have discovered that information before or during Dr.
Dunlap’s testimony. According to Tucker, this information was nec-
essary to destroy Dr. Dunlap’s credibility and cast doubt on the
State’s argument that antisocial personality disorder could not excuse
Tucker’s criminal conduct.

   Trial counsel have an obligation to investigate possible methods for
impeaching a prosecution witness, and failure to do so may constitute
ineffective assistance of counsel. Huffington v. Nuth, 

,
580 (4th Cir. 1998); Hoots v. Allsbrook, 

, 1221 (4th Cir.
1986). The reasonableness of the investigation depends, in part, upon
the importance of the witness to the prosecution’s case: "Although a
lawyer’s failure to investigate a witness who has been identified as
crucial may indicate an inadequate investigation, the failure to investi-
gate everyone whose name happens to be mentioned by the defendant
does not suggest ineffective assistance." 

.
As we noted in Huffington, most of the witnesses whom federal courts
have deemed "crucial" were "alibi witnesses or eyewitnesses critical
to the determination of guilt," such as self-defense witnesses. 

with Tucker’s contention that trial counsel were
required to discover Dr. Dunlap’s disciplinary record or conduct
cross-examination on that issue absent some prior or contemporane-
ous indication that his professional status was in question. At the out-
set, Dr. Dunlap was not a crucial witness under Huffington. He was
one of three rebuttal witnesses called by the State to refute Tucker’s
contention that his antisocial personality disorder was a mental illness
warranting leniency in sentencing. Of these three witnesses, Dr. Dun-
lap was the only one who had never met nor examined Tucker. Dr.
Dunlap’s role in this case was hardly analogous to the role of "alibi
                            TUCKER v. OZMINT                            15
witnesses or eyewitnesses critical to the determination of guilt." Huf-

.7

   Although trial counsel were aware that Dr. Dunlap would testify,
they had no reason to suspect that his professional status would be an
issue. It is undisputed that neither the solicitor nor trial counsel were
aware of Dr. Dunlap’s probation at the time of trial. (Indeed, the
solicitor testified that Dr. Dunlap appeared to be practicing without
restriction at the time he was called to testify in this case.) It is also
undisputed that Dr. Dunlap’s direct testimony did not alert counsel to
any issue concerning his status. As the PCR court noted, the only way
to find out about Dr. Dunlap’s record would have been to subpoena
documents from, or file a FOIA request with, the Board of Medical
Examiners. Trial counsel do not act unreasonably by failing to con-
duct such investigations on non-crucial expert witnesses.

   Moreover, Tucker’s counsel did attempt to impeach Dr. Dunlap’s
expert testimony by establishing that his testimony was purely specu-
lative. Dr. Dunlap admitted that he had never examined Tucker nor
even spoken to him, nor had Dr. Dunlap heard Dr. Noelker’s testi-
mony. Based on these admissions, trial counsel moved to exclude Dr.
Dunlap’s testimony. Although their motion was denied, counsel
argued to the jury that Dr. Dunlap’s testimony should not be credited
because he knew so little about Tucker’s particular condition. As the
district court noted, "this is not a case where trial counsel made no
effort to investigate and pursue avenues of impeachment; rather, trial
counsel simply failed to uncover the precise impeachment evidence
that current counsel was subsequently able to obtain." It is not enough
  7
    We do not in any way suggest that the only witnesses who may be
deemed "crucial" under Huffington are alibi witnesses or eyewitnesses to
the alleged crime. Of course, the sentencing phase of a capital trial natu-
rally raises different considerations for the jury than the guilt phase,
when alibi witnesses or eyewitnesses to the crime are often critical.
Whether a sentencing phase witness was "crucial" must be evaluated in
light of the issues relevant to sentencing. Post-conviction counsel’s
backward-looking characterization of the role of any particular witness
should have no bearing on this question. See 

-
90 (cautioning reviewing courts to evaluate trial counsel’s performance
"as of the time of counsel’s conduct").
16                        TUCKER v. OZMINT
that post-conviction counsel managed to discover Dr. Dunlap’s disci-
plinary problems; as with all claims of ineffective assistance of coun-
sel, we are mindful that "[a] fair assessment of attorney performance
requires that every effort be made to eliminate the distorting effects
of hindsight." 

.

   Even if Tucker could demonstrate that his counsel’s performance
was unreasonable under the circumstances, he has not shown that he
was prejudiced by trial counsel’s failure to expose Dr. Dunlap’s pro-
bation. Counsel highlighted the speculative nature of Dr. Dunlap’s
testimony, arguing to the jury that an opinion based upon general
principles rather than an examination of Tucker himself should not be
given any weight. In addition, Dr. Dunlap’s testimony concerning a
diagnosis of antisocial personality disorder was cumulative to the
prior testimony of Drs. Frierson and Shea. Like Drs. Frierson and
Shea, Dr. Dunlap testified that antisocial personality disorder is
merely descriptive, not causative. Thus, with or without Dr. Dunlap’s
testimony, the jury was presented with the State’s theory that
although Tucker was abused as a child and had an antisocial personal-
ity disorder, this disorder did not cause him to engage in criminal
activity.

   Considering the aggravating and mitigating circumstances present
in this case, we conclude that any error on this score would not "un-
dermine confidence in the outcome" of the proceeding. 

. The state court’s decision was not an unreasonable
application of Strickland, and the district court properly denied habeas
relief on this claim.

                                  III.

   Tucker’s ineffective assistance claims fail to satisfy the require-
ments of Strickland, and the state court’s denial of Tucker’s claims
was not an unreasonable application of federal law. Accordingly, the
judgment of the district court is

                                                          AFFIRMED.