236	                         December 14, 2017	                             No. 65

               IN THE SUPREME COURT OF THE
                     STATE OF OREGON

              CHARLES EDWARD RICHARDSON,
                    Respondent on Review,
                               v.
                     Brian BELLEQUE,
                       Superintendent,
                  Oregon State Penitentiary,
                     Petitioner on Review.
            (CC 09C20407; CA A151817; SC S064185)

    On review from the Court of Appeals.*
    Argued and submitted January 12, 2017.
   Patrick M. Ebbett, Assistant Attorney General, Salem,
argued the cause and filed the briefs for petitioner on review.
Also on the briefs were Ellen F. Rosenblum, Attorney
General, Benjamin Gutman, Solicitor General and Frederick
M. Boss, Deputy Attorney General.
   Jason Weber, O’Connor Weber LLC, Portland, argued the
cause and filed the brief for respondent on review.
    Dennis N. Balske and Jeffrey Erwin Ellis, Portland,
filed the brief for amicus curiae Oregon Criminal Defense
Lawyers Association.
  Before Balmer, Chief Justice, and Kistler, Walters, Landau,
Nakamoto, and Flynn, Justices.**
    NAKAMOTO, J.
   The decision of the Court of Appeals and the judgment of
the circuit court are affirmed.

______________
	**  On appeal from Marion County Circuit Court, Linda L. Bergman, Senior
Judge. 277 Or App 615, 373 P3d 1113 (2016).
	    **  Baldwin, J., retired March 31, 2017, and did not participate in the decision
of this case. Brewer, J., retired June 30, 2017, and did not participate in the deci-
sion of this case. Duncan, J., did not participate in the consideration or decision of
this case.
Cite as 362 Or 236 (2017)	237

    Case Summary: Petitioner, who was convicted of first-degree manslaughter
and second-degree assault and sentenced as a dangerous offender, sought post-
conviction relief, alleging that counsel provided inadequate assistance at sen-
tencing. At the sentencing proceeding, the prosecutor presented a psychiatrist
who testified that petitioner suffered from an antisocial personality disorder, in
part based on petitioner’s conduct as a juvenile. Petitioner’s defense counsel knew
beforehand that the expert would testify adversely to petitioner, but he did not
obtain significant records pertaining to petitioner when he was a juvenile, con-
sult with a psychological expert, or secure testimony from an expert to rebut that
evidence. In the post-conviction proceeding, petitioner presented evidence from a
psychologist who reviewed records from one of petitioner’s juvenile incarcerations
and interviewed petitioner, and who ultimately concluded that petitioner had not
suffered from a conduct disorder when he was a youth, and therefore could not be
diagnosed with an antisocial personality disorder as an adult. Held: Petitioner’s
counsel had failed to conduct an adequate investigation and, in light of the nature
and complexity of the dangerous-offender sentencing proceeding and the infor-
mation that counsel knew, counsel’s decision not to consult an expert concerning
the antisocial personality disorder diagnosis was not a reasonable exercise of
professional skill and judgment. Had counsel adequately investigated petitioner’s
past and consulted a psychological expert, he would have obtained petitioner’s
juvenile mental health records and would have learned that the expert could pro-
vide ammunition to oppose an enhanced dangerous-offender sentence, by rebut-
ting the testimony of the psychiatrist and providing an explanation of petitioner’s
conduct that was not as damaging as an antisocial personality disorder.
    The decision of the Court of Appeals and the judgment of the circuit court
are affirmed.
238	                                         Richardson v. Belleque

	         NAKAMOTO, J.
	        In this action for post-conviction relief, petitioner
successfully contended that his defense counsel had ren-
dered constitutionally inadequate representation during a
presentence hearing concerning whether petitioner was a
dangerous offender who suffered from a “severe personal-
ity disorder” as provided in ORS 161.725(1)(a). Petitioner’s
defense counsel cross-examined the psychiatrist who testi-
fied for the state, but counsel had not investigated signifi-
cant records regarding petitioner’s background or consulted
with an expert before the hearing, nor did he introduce evi-
dence from a defense expert at the hearing. The jury found
that petitioner suffered from a severe personality disorder,
and the trial court sentenced petitioner to a lengthy prison
term as a dangerous offender.
	        The post-conviction court concluded that defense
counsel had provided inadequate assistance by failing
(1) to reasonably investigate and to consult with an expert
before deciding that cross-examination alone was appropri-
ate and (2) to present testimony from a defense expert to
rebut the psychiatrist’s testimony that petitioner had an
antisocial personality disorder. After concluding that peti-
tioner had been prejudiced as a result, it vacated petitioner’s
dangerous-offender sentence and remanded the case for
resentencing. The Court of Appeals affirmed based on one
of the post-conviction court’s conclusions: that defense coun-
sel had provided inadequate assistance through failure to
investigate and consult an expert and that petitioner suf-
fered prejudice as a result. Richardson v. Belleque, 277 Or
App 615, 627-29, 373 P3d 1113 (2016).
	        On review, the state1 argues that the Court of
Appeals erred for two alternative reasons: (1) defense coun-
sel made a reasonable tactical decision to rely on cross-
examination without consulting an expert and (2) regard-
less, petitioner did not establish the required prejudice,
which the state describes as a showing that, but for the defi-
cient representation, it was “reasonably probable” that the

	1
     We refer to defendant Belleque, the Superintendent of the Oregon State
Penitentiary, as “the state” for ease of reference.
Cite as 362 Or 236 (2017)	239

outcome of the sentencing phase of trial “would have been
different.”
	        As did the Court of Appeals, we conclude that defense
counsel rendered inadequate assistance by failing to ade-
quately investigate and to consult an expert in preparation
for the dangerous-offender hearing. We also conclude that
defense counsel’s deficiency had “a tendency to affect the
result of the prosecution”—the possibility that it affected
the result is more than merely theoretical. Accordingly, peti-
tioner established prejudice and is entitled to post-conviction
relief. We therefore affirm the judgment of the trial court
and the decision of the Court of Appeals.
                         I. FACTS
	         For background, we begin by briefly describing the
facts adduced during the guilt phase of petitioner’s criminal
prosecution. As the Court of Appeals described the incident
that led to the convictions, in 2006, petitioner and his wife
quarreled in a tavern, and then “petitioner walked out the
back door to work on his truck. Petitioner later returned,
exchanged words with his wife, and then left, slamming the
door on his way out. This drew the attention of the victim,
an elderly man, who followed petitioner out the door.” 277 Or
App at 618. Petitioner then “punched him, causing him to
fall.” Id. Thereafter, petitioner went back into the bar, told
his wife to leave with him, and they walked out “the same
door, walking by the victim as they departed. The victim
suffered a massive head injury and died the next day.” Id.
	        Petitioner was charged with first-degree manslaugh-
ter, a Class A felony, and second-degree assault. The state’s
theory of the case was that the attack was unprovoked. The
defense theory was that petitioner had not acted knowingly
(the assault charge) or recklessly (the manslaughter charge)
and, instead, had hit the victim in self-defense.
	       The defense relied on evidence that petitioner had
witnessed numerous acts of domestic violence by his par-
ents when he was a child, and later by other inmates while
in prison, to argue that, when petitioner hit the victim, he
reasonably feared that the victim intended to use a weapon
against him. More particularly, petitioner testified that he
240	                                            Richardson v. Belleque

was quite close with his mother, had witnessed his father hit
his mother on nearly a daily basis, and that one time he had
hit his father when his father was hitting his mother. He
also testified that he had had to fight in self-defense while
in prison. In addition, petitioner’s sisters provided testimony
indicating that petitioner’s early home life had been cha-
otic. One sister testified that there was considerable abuse
between their parents, primarily instigated by their mother,
and that she left home as a teenager due to verbal abuse
by their mother. Another sister testified that their parents
were constantly physically fighting, and described their
mother as “the violent one.” She also testified that petitioner
had been confined in the Skipworth juvenile facility multiple
times because he “wouldn’t go to school.” She also indicated
that he had been in juvenile facilities at St. Mary’s Home for
Boys and at MacLaren School for Boys.2
A.  The Dangerous-Offender Sentence
	       A jury found petitioner guilty of both charges. The
state then sought to have petitioner sentenced as a “dan-
gerous offender” on the manslaughter charge under ORS
161.725 to 161.737.3 The presentence hearing at which the
jury would determine whether petitioner was a dangerous
offender was critically important to petitioner.
	        In part, ORS 161.725(1)(a) provides that a sentenc-
ing court may impose an enhanced dangerous-offender sen-
tence if a defendant is being sentenced for a Class A felony
and suffers from “a severe personality disorder indicating a
propensity toward crimes that seriously endanger the life
or safety of another.” First-degree manslaughter generally
requires imposition of a mandatory minimum prison sen-
tence of 10 years and carries a maximum indeterminate
prison sentence of 20 years. ORS 137.700(3)(a)(D); ORS
161.605(1); ORS 163.118(3). However, if the state proves
that the defendant is a dangerous offender, upon proof of
certain other facts, the determinate prison term for the

	2
      The MacLaren School for Boys is now known as the MacLaren Youth
Correctional Facility.
	3
       Our references throughout this opinion are to the versions of ORS 161.725
to 161.737 that were in effect in 2006 at the time of the crimes, although those
statutes for the most part remain the same at present.
Cite as 362 Or 236 (2017)	241

crime, a Class A felony, can be increased, and the associated
maximum indeterminate prison term becomes 30 years.4
	        The state prevailed at the dangerous-offender hear-
ing. The resulting dangerous-offender sentence that peti-
tioner received was considerably longer than the sentence
he otherwise would have received. The sentencing court set
the determinate portion of petitioner’s dangerous-offender
sentence at 260 months in prison (four months short of 22
years) and imposed an indeterminate prison term of 30
years.
	      After he was sentenced, petitioner’s direct appeal
was unsuccessful. State v. Richardson, 226 Or App 85, 202
P3d 290, rev den, 346 Or 213 (2009).
B.  Petitioner’s Dangerous-Offender Hearing
	       The issue under our consideration in petitioner’s
action for post-conviction relief relates to the dangerous-
offender hearing and defense counsel’s preparation for it. We
therefore describe that hearing in detail.
	       By statute, a mental health professional will be
appointed to evaluate a criminal defendant in a dangerous-
offender case and will be involved in the process leading to
the determination of dangerous-offender status. Under ORS
161.735(1), the trial court is required to order “an examina-
tion by a psychiatrist or psychologist.” The psychiatrist or
psychologist must submit to the court “a written report of
findings and conclusions, including an evaluation of whether
the defendant is suffering from a severe personality disor-
der indicating a propensity toward criminal activity.” ORS

	4
      Under ORS 161.737(2), when a court imposes a dangerous-offender sen-
tence, “the sentencing judge shall indicate on the record the reasons for depar-
ture and shall impose, in addition to the indeterminate sentence imposed under
ORS 161.725, a required incarceration term that the offender must serve before
release to post-prison supervision.” Under ORS 161.725(1), if a person is sen-
tenced as a dangerous offender under ORS 161.725 to 161.737 for a Class A felony,
“the maximum term of an indeterminate sentence of imprisonment for a danger-
ous offender is 30 years.” In this case, the jury made findings in support of depar-
ture that petitioner had committed the offense while on felony probation, that he
had engaged in persistent involvement in similar offenses, and that he was being
sentenced for a felony that seriously endangered the life or safety of another, and
the court based the determinate portion of the dangerous offender sentence on
those findings.
242	                                  Richardson v. Belleque

161.735(3). A presentence dangerous-offender hearing is
then held, and, unless the criminal defendant waives the
right to a jury, a jury makes the determination whether
the criminal defendant has a “severe personality disorder
indicating a propensity toward crimes that seriously endan-
ger the life or safety of another.” ORS 161.725(1)(a); ORS
161.735(5), (6).
	        Accordingly, the trial court ordered a psychiatrist,
George Suckow, M.D., to evaluate petitioner before the
dangerous-offender hearing. After examining petitioner,
Suckow submitted a written report to the court and counsel
for the parties. His report was adverse to petitioner.
	         Suckow’s report recounted that petitioner had a his-
tory of physical abuse by his mother, and that he had been
placed in the St. Mary’s Home for Boys at the age of 12 after
running away from home. The report further indicated that
petitioner had a history of getting into fights during grade
school, as well as at St. Mary’s. It indicated that petitioner
had issues with truancy from school, and he subsequently
was placed at MacLaren, an Oregon youth correctional facil-
ity, and then later in a federal youth correctional institution
in California. Suckow’s report also recounted that petitioner
had an extensive criminal history, beginning when he was a
juvenile and continuing into his adult life, and “a pervasive
pattern of disregard for and violation of the rights of others”
that was “present prior to and after the age of 15.” Suckow
diagnosed petitioner with amphetamine abuse as well as an
antisocial personality disorder. Suckow ultimately opined
that petitioner “does have a severe personality disorder indi-
cating a propensity toward crimes that seriously endanger
the life and safety of others.”
	        Suckow testified at the dangerous-offender hearing,
and its primary focus was on Suckow’s evidence. Suckow
testified that his examination of petitioner involved a foren-
sic interview that lasted approximately an hour, a review of
petitioner’s history and background including investigation
reports of the current crime and petitioner’s criminal record,
and an assessment of petitioner’s present mental status. He
explained how diagnoses were made under the American
Psychiatric Association’s Diagnostic and Statistical Manual
Cite as 362 Or 236 (2017)	243

of Mental Disorders (4th ed text rev 2000), hereafter referred
to as DSM-IV-TR, and the various categories of disorders in
that manual. He explained, referring to the DSM-IV-TR, that
“[a] personality disorder is a pervasive pattern of behavior
that starts in childhood and lasts for life. And it’s not a psy-
chosis, it’s not a major mental illness; it’s a way of behaving
that that person has.” He indicated that people with anti-
social personality disorders are “normal except they seem to
do things that are wrong and they have little regard for the
rights of others.” He described them as being prone to get-
ting into fights and getting into trouble in school, and often
having substance abuse problems. He opined that they tend
to be deceitful and lacking in long-range goals. He noted,
however, that they often do well in confinement due to the
structure provided.
	         Suckow explained that, in reaching a diagnosis of
petitioner, he looked at petitioner’s pattern of behavior over
the years and compared that to what petitioner told him. He
concluded that petitioner had been fairly open and honest
with him and had acknowledged that he had had “a lot of
trouble in school and with the law.” Suckow further testi-
fied that petitioner had said that, when he had been sent
to St. Mary’s at the age of 12, he “didn’t like the discipline
there and got into fights just like he had in grade school.”
He described petitioner’s later juvenile history as involv-
ing incarceration at MacLaren, followed by several years in
a federal youth institution based on theft of a motorcycle.
Petitioner also was incarcerated in an adult correctional
facility in California, and he served time in a Washington
state penitentiary for assault. In Oregon, petitioner pleaded
guilty to numerous offenses over a number of years, and he
had an attempted-murder charge reduced to second-degree
assault. Suckow testified that petitioner acknowledged
that he started to use amphetamines in the 1990s. Suckow
opined that petitioner had had “a conduct disorder before
the age of 15” and diagnosed petitioner with an antisocial
personality disorder.
	        Through cross-examination of Suckow, defense
counsel’s main focus was on whether there was sufficient
evidence that petitioner suffered from a “severe personality
244	                                                 Richardson v. Belleque

disorder,” as required for a dangerous-offender sentence.
In his cross-examination, defense counsel highlighted the
requirements under the DSM-IV-TR for a diagnosis of anti-
social personality disorder and introduced, without objec-
tion, documents showing the criteria for diagnoses of anti-
social personality disorder and conduct disorder found in
the DSM-IV-TR. He noted that a criterion for diagnosis of an
antisocial personality disorder was “evidence of a conduct
disorder with onset before age 15 years.”5 Defense counsel
then asked Suckow whether, if a person did not meet that
criterion, the person could be diagnosed with an antisocial
personality disorder. Suckow indicated general agreement
with counsel’s suggestion that that criterion must be met.
Suckow then suggested that the age criterion was “not an
absolute,” because people do not simply change on the date
they reach a specified age.
	        Defense counsel questioned Suckow about how much
(or how little) Suckow knew concerning petitioner before peti-
tioner was 15 years old. Counsel zeroed in on the criteria for
a “conduct disorder” as specified in the DMS IV-TR, which
required that three criteria be satisfied in order to make a

	5
        For ease of reference, we include a list of the pertinent criteria for diagnosis
of an antisocial personality disorder under the DSM-IV-TR:
    “A.  There is a pervasive pattern of disregard for and violation of the rights
    of others occurring since age 15 years, as indicated by three (or more) of the
    following:
    	     “(1)  failure to conform to social norms with respect to lawful behaviors
    as indicated by repeatedly performing acts that are grounds for arrest
    	     “(2)  deceitfulness, as indicated by repeated lying, use of aliases, or con-
    ning others for personal profit or pleasure
    	     “(3)  impulsivity or failure to plan ahead
    	 “(4) irritability and aggressiveness, as indicated by repeated physical
    fights or assaults
    	     “(5)  reckless disregard for safety of self or others
    	     “(6)  consistent irresponsibility, as indicated by repeated failure to sus-
    tain consistent work behavior or honor financial obligations
    	     “(7)  lack of remorse, as indicated by being indifferent to or rationalizing
    having hurt, mistreated, or stolen from another.
    “B.  The individual is at least age 18 years.
    “C.  There is evidence of conduct disorder with onset before age 15 years.
    “D.  The occurrence of antisocial behavior is not exclusively during the course
    of schizophrenia or a manic episode.”
DSM-IV-TR at 706.
Cite as 362 Or 236 (2017)	245

diagnosis of the disorder.6 One of the criteria for a conduct
disorder is the initiation of physical fights. Counsel asked
Suckow how that criterion could be satisfied, given that
Suckow’s report did not specify who had initiated the fights
Suckow had mentioned in the report. Suckow responded:
“Well, he told me he got into fights. Now, to me, that doesn’t
mean he was picked on; means he started them.” Suckow
acknowledged that his report included that petitioner had
reported being bullied by other children later at MacLaren,

	6
         For ease of reference, we include a list of the pertinent criteria for diagnosis
of a conduct disorder under the DSM-IV-TR:
     “A.  A repetitive and persistent pattern of behavior in which the basic rights
     of others or major age-appropriate societal norms or rules are violated, as
     manifested by the presence of three (or more) of the following criteria in the
     past 12 months, with at least one criterion present in the past 6 months:
     “Aggression to people and animals
     	     “(1)  often bullies, threatens, or intimidates others
     	     “(2)  often initiates physical fights
     	     “(3)  has used a weapon that can cause serious physical harm to others
     (e.g., a bat, brick, broken bottle, knife, gun)
     	     “(4)  has been physically cruel to people
     	     “(5)  has been physically cruel to animals
     	     “(6)  has stolen while confronting a victim (e.g., mugging, purse snatch-
     ing, extortion, armed robbery)
     	     “(7)  has forced someone into sexual activity
     “Destruction of property
     	     “(8)  has deliberately engaged in fire setting with the intention of causing
     serious damage
     	 “(9) has deliberately destroyed others’ property (other than by fire
     setting)
     “Deceitfulness or theft
     	     “(10)  has broken into someone else’s house, building, or car
     	     “(11)  often lies to obtain goods or favors or to avoid obligations (i.e., ‘cons’
     others)
     	 “(12)  has stolen items of nontrivial value without confronting a victim
     (e.g., shoplifting, but without breaking and entering; forgery)
     “Serious violations of rules
     	 “(13) often stays out at night despite parental prohibitions, beginning
     before age 13 years
     	 “(14)  has run away from home overnight at least twice while living in
     parental or parental surrogate home (or once without returning for a lengthy
     period)
     	     “(15)  is often truant from school, beginning before age 13 years.”
DSM-IV-TR at 98-99 (boldface in original).
246	                                 Richardson v. Belleque

and also that the report did not specify that petitioner had
initiated any of the fights in which he had been involved
before that time. Counsel then pressed the point, asking if
Suckow was merely “guessing,” but Suckow responded: “No.
I’m drawing a conclusion based upon his lifestyle and what
he told me.” Counsel then ran through a number of other
criteria for a conduct disorder, which Suckow acknowledged
had not been satisfied.
	        Counsel then asked about the criterion, “run away
from home overnight at least twice while living in paren-
tal or parental-surrogate home” or “once without returning
for a lengthy period.” Counsel noted that Suckow’s report
mentioned only one incident of petitioner running away from
home before age 12, but Suckow responded that “it sounded
to me like he’d done it more than once.” Counsel then noted
that Suckow’s report suggested that petitioner had skipped
school after leaving St. Mary’s at the age of 13 or 14, and
he asked how that could satisfy the conduct disorder crite-
rion of “often truant from school, beginning before age 13.”
(Emphasis added.) Suckow’s response was that he believed
the age cut-off to be an arbitrary figure and that he consid-
ered that criterion satisfied.
	         On redirect examination, the prosecutor shored
up Suckow’s testimony. The prosecutor referred back to the
diagnosis of antisocial personality disorder and asked, “is it
correct that it does not require a diagnosis of conduct disor-
der; it just requires some evidence thereof?” Suckow replied:
“Yes.”
	        In addition to Suckow’s testimony, the jury received
information on petitioner’s criminal history, which included
numerous property crimes and assaults dating back to the
1970s. (Much of petitioner’s criminal history had already
been revealed during the guilt phase of the trial, when
petitioner testified in his own defense.) The prosecutor also
presented evidence about a physical altercation between
petitioner and several uniformed deputies that occurred
during a recess at trial. Evidence was also presented from
victims of some of petitioner’s prior crimes, including evi-
dence of knife attacks on multiple members of a family after
petitioner was caught stealing tires, an incident in which
Cite as 362 Or 236 (2017)	247

petitioner rammed his vehicle into two police cars while try-
ing to elude their pursuit, and an occasion when petitioner
attacked a deputy sheriff in a county jail.
	       Although defense counsel cross-examined Suckow,
he did not offer expert psychological testimony to rebut
Suckow’s testimony and diagnosis of petitioner. The only
witness whom defense counsel called was petitioner’s wife.
	        In closing argument, the prosecutor emphasized
that the determination of whether petitioner suffered from a
personality disorder as described in the dangerous offender
statute was a matter for the jury, not the expert, to decide. He
noted petitioner’s lengthy criminal history, and he pointed
out that the gaps in that history were during periods of time
when petitioner was imprisoned.
	        Defense counsel’s closing argument focused on
Suckow’s testimony and the prosecution’s burden of proof.
Defense counsel pointed out that Suckow had acknowledged
that he accepted the DSM-IV-TR criteria for conduct disor-
der, but that (1) Suckow lacked any basis for concluding that
petitioner had initiated the fights he had been in, (2) Suckow
had not documented more than one instance of petitioner
running away from home, and (3) Suckow’s report revealed
instances of truancy only after petitioner had left St. Mary’s
at the age of 13 or 14. Defense counsel argued that on mat-
ters when Suckow “had to draw certain conclusions, he was
saying he did not have the facts to support him. But he then
kind of said he was assuming, as an adult, it’s probable,
maybe, it was there as a child—recall that? ‘Probable’ is not
beyond a reasonable doubt.” Defense counsel also noted that
the jury was not bound by Suckow’s opinion, and he urged
the jury to use the criteria from the DSM-IV-TR to conclude
that the criteria for a conduct disorder had not been met and
that, therefore, “[t]he antisocial behavior, then is not there
either.”
	        After closing arguments, the trial court instructed
the jury to make findings as to whether petitioner was “suf-
fering from a severe personality disorder indicating a pro-
pensity toward crimes that seriously endanger the life or
safety of another and that, because of the dangerousness
248	                                     Richardson v. Belleque

of [petitioner], an extended period of confined correctional
treatment or custody is required for the protection of the
public.” ORS 161.725(1). The court also included an instruc-
tion that the jury was not required to accept the opinions
of experts. The jury unanimously found that petitioner suf-
fered from a severe personality disorder indicating a pro-
pensity toward crimes that seriously endanger the life or
safety of another.
C.  The Post-Conviction Proceeding
	        Petitioner initiated the present proceeding, alleging
that his defense counsel in the underlying criminal proceed-
ing had provided inadequate assistance of counsel, in viola-
tion of Article I, section 11, of the Oregon Constitution. As
pertinent here, petitioner alleged:
   “Defense counsel failed to conduct an investigation to sup-
   port his decision not to obtain a defense psychological evalu-
   ation of petitioner to rebut testimony by prosecution expert,
   Dr. George Suckow, that petitioner suffered from an anti-
   social personality disorder. A defense psychologist would
   have provided testimony that petitioner does not meet the
   diagnostic criteria for an antisocial personality disorder
   and that petitioner did not suffer from a severe personality
   disorder. As a result of counsel’s failure to retain a defense
   psychologist the jury relied exclusively upon the testimony
   of Dr. Suckow to determine that petitioner did suffer from
   a severe personality disorder. Petitioner was thereafter
   sentenced as a dangerous offender under ORS 161.725. An
   attorney exercising reasonable professional skill and judg-
   ment would have retained a psychologist for the reasons
   outlined above.”
	        In support of that claim, petitioner introduced a writ-
ten report from a clinical psychologist, Dr. Norvin Cooley. In
his written report, Cooley indicated that he had been hired
to evaluate petitioner and examine records to determine if
“there were factors that should have been considered by the
[jury] which were not provided in [petitioner’s] defense that
could have influenced the [jury’s] opinion as to whether or
not [petitioner] was a dangerous offender.” His record review
covered (1) the presentencing investigation that had been
done before petitioner’s dangerous offender hearing; (2) peti-
tioner’s records at St. Mary’s Home for Boys; (3) Suckow’s
Cite as 362 Or 236 (2017)	249

report and testimony; and (4) the prosecutor’s and defense
counsel’s opening and closing arguments at the dangerous
offender hearing. Cooley further noted that he and other psy-
chologists in Oregon would have been available as defense
experts at the time of petitioner’s dangerous-offender hear-
ing and would have obtained and reviewed critical historical
background records concerning petitioner.

	        With respect to the presentencing investigation
report, Cooley observed that it included 14 felony convictions,
21 misdemeanors, and a juvenile adjudication “for interstate
transportation of a stolen vehicle [when petitioner] was 15
years old.” Cooley further noted that the report indicated
that petitioner had been in the Skipworth juvenile facility
for hitting his father during a domestic violence incident
involving both of his parents.7

	        Cooley’s report also recounted numerous facts from
his review of the St. Mary’s records.8 He indicated that the
records showed that petitioner, after being confined in the
Skipworth juvenile facility, had been moved to St. Mary’s in
1965, at the age of 12. At St. Mary’s, petitioner had trouble
getting along with other children and was easily provoked to
anger. A caseworker note indicated that petitioner had been
suspended from two different schools, once for “fighting,
swearing, and truancy.” A referral letter sent to St. Mary’s
indicated that petitioner had “run away from home on sev-
eral occasions in May 1965” and, on one of those occasions,
he had stolen two bicycles. But Cooley also noted that the
St. Mary’s records revealed numerous instances of domes-
tic violence, in particular by petitioner’s mother, leading to
police contacts. He recounted that petitioner’s caseworkers
at St. Mary’s had found petitioner’s mother to be “virtually
impossible to work with” and had concluded that petitioner’s
problems as a youth stemmed from his home life. The
records also described numerous instances of her abusive
behavior toward petitioner, both in public and at home. One
of petitioner’s confinements to Skipworth was “for his own

	7
       Some evidence of that incident had been adduced during the guilt phase of
petitioner’s trial. See 362 Or at 239.
	8
       The St. Mary’s records themselves did not come into evidence in this case.
250	                                 Richardson v. Belleque

protection because mother threatened to pull him from any
foster home.”
	         Cooley indicated that the St. Mary’s file included a
number of evaluations of petitioner. As part of St. Mary’s
screening, a psychiatrist, Robert Johnson, M.D., had seen
petitioner. Johnson described petitioner as a “seriously dis-
turbed youngster” who had a very difficult relationship with
his mother. Johnson had “diagnosed [petitioner] as demon-
strating an adjustment reaction of early adolescence with
behavior disturbance, severe.” Johnson had thought that
petitioner had a “poor prognosis” and likely “would be in
conflict with authority indefinitely” but that a modification
of his living situation “may attenuate this problem.” Cooley
also noted that the file contained information from a psychol-
ogist, Dr. Fischer. Fischer had found petitioner to be “very
resistant to authority” and “unstable” but thought that, if
petitioner developed a close relationship with a counselor,
his prognosis would be “good.” Fischer also had noted that
petitioner’s mother contributed significantly to petitioner’s
resistance to authority.
	        As for his review of Suckow’s testimony, Cooley char-
acterized the testimony as “conclud[ing] by inference that
[petitioner] must have displayed a conduct disorder.” Cooley,
however, disagreed with Suckow on that point. Cooley
acknowledged that the St. Mary’s records showed that peti-
tioner’s “adjustment while there was not particularly pos-
itive.” But highlighting the indications in the record that
petitioner’s mother was highly abusive, Cooley opined that
petitioner’s behavioral problems were a result of his home
life. Cooley observed that “[t]here are other psychological,
social, and familial issues which can create behaviors that,
on the surface, appear antisocial when in fact they are due
to impinging issues.” Cooley emphasized that Johnson’s psy-
chiatric evaluation of petitioner in the St. Mary’s records—
which Suckow had not reviewed—diagnosed petitioner “with
an adjustment disorder, not a conduct disorder.”
	        Cooley noted that his review of the case indicated
that Suckow’s opinion had been important to the state’s
contention that petitioner suffered from a severe person-
ality disorder. Cooley directly rebutted Suckow’s diagnosis
Cite as 362 Or 236 (2017)	251

of petitioner. Cooley concluded that, if a defense expert had
been obtained, the expert could have testified that, had
Suckow reviewed the St. Mary’s records, Suckow would not
have been able to accurately diagnose an antisocial person-
ality disorder. And, Cooley opined, it would not have been
possible, based on all of the available data, “to conclude
that [petitioner] demonstrates the symptoms and behaviors
consistent with the diagnosis of an antisocial personality
disorder.”

	        In response, the state offered into evidence the
deposition of petitioner’s defense counsel, Jagger. Jagger had
reviewed petitioner’s background and family information,
as well as his criminal history. After reviewing Suckow’s
report, he considered whether or not to hire an expert to
present evidence on petitioner’s behalf at the dangerous-
offender hearing. He could not recall whether he had talked
to an expert about the case, but he remembered that he did
not call an expert. He explained that he had tried approx-
imately 20 cases involving dangerous-offender hearings in
the past and that he sometimes used an expert but some-
times did not. He stated that sometimes, in the minority of
cases, “I think I can make better hay with what they had
and they presented than confusing things by having my own
expert.” He stated that he “did not think that there was any
benefit to actually hir[ing] someone to do an evaluation” in
petitioner’s case. Jagger had not obtained petitioner’s juve-
nile records from St. Mary’s.

	        In light of Jagger’s deposition testimony, the state
argued at the post-conviction hearing that defense counsel
had made a strategic decision not to rely on defense expert
testimony and that his decision to rely instead on cross-
examination of Suckow was reasonable. The state argued
that “trial counsel did an extraordinary job in establishing
that Dr. Suckow, by his own criteria, had not met the crite-
ria for the diagnosis that he testified to.” The state argued
that, had defense counsel called an expert such as Cooley to
testify at the dangerous-offender hearing, such testimony
“would have filled in the elements and the blanks in the
state’s case,” such as establishing that petitioner had, in fact,
run away from home more than once and been truant from
252	                                      Richardson v. Belleque

school. The state pointed out that the psychological and psy-
chiatric evidence from the St. Mary’s records confirmed that
petitioner had numerous behavioral problems and was very
resistant to authority. Thus, the state asserted, bringing
that information before the jury would, in fact, have been
ineffective—providing the jury with additional evidence of a
conduct disorder that existed before petitioner reached the
age of 15.
	        At the post-conviction hearing, counsel for petitioner
argued that, in light of the diagnosis by the psychiatrist
that Cooley had found in the St. Mary’s records, “the jury
would not have been able to legally make a determination
that [petitioner] had a severe personality disorder, an anti-
social personality disorder, and could not therefore have
legally, under the statutory requirements, have made the
requisite findings for imposition of a dangerous offender sen-
tence upon him.” Further, petitioner argued, an opinion of a
defense psychologist that petitioner did not have a conduct
disorder would have established that there was no antisocial
personality disorder and, “[w]ithout an antisocial personal-
ity disorder, the jurors could not have made their finding.”
	        The post-conviction court orally ruled in favor of
petitioner and rejected the crux of the state’s argument:
   “I think defense counsel did an excellent job with Dr. Suckow
   on cross and got as much as he could get, and it was really
   quite a bit, showing that Suckow’s diagnosis had some gaps
   in it, although the doctor still held with the same diagnosis
   even after he was impeached.
   	 “But what he couldn’t get on cross is that bottom line
   that says this behavior is explained through a totally
   different diagnosis that would throw out the possibility
   of dangerous offender. So if all of that behavior could be
   explained with an adjustment reactive disorder, we’re not
   in dangerous offender territory anymore.
   	 “I agree that Dr. Cooley had a number of facts that were
   not flattering to petitioner. * * * But all of those facts could
   then have been explained by an alternative diagnosis. And
   you can’t get there on cross.
   	 “So despite the very good job I think the attorney did on
   cross, it still left a hole that he could have filled by having
Cite as 362 Or 236 (2017)	253

   his own expert. I think that was an inadequacy and I think
   this case needs to be resentenced.”
	        Similarly, the post-conviction court’s written find-
ings explain the import of petitioner’s prior adjustment reac-
tive disorder diagnosis and refer to other circumstances of
petitioner’s background that were unknown to defense coun-
sel, both of which undercut Suckow’s diagnosis of petitioner:
   	 “Pet. found to be dangerous offender + c[ourt] sentenced
   as d[angerous] o[ffender] largely based on D.A.’s expert,
   Dr. Suckow. Trial att[orney] did not consult or call an expert.
   Suckow found that pet[itioner] had a personality disorder
   (written report says severe) which requires an underlying
   diagnosis of conduct disorder which in turn requires onset
   before age 15. He did not have pet[itioner’s] juvenile records
   from St. Mary’s that contain a diagnosis of adjustment reac-
   tive disorder not conduct disorder. This court agrees with
   att[orney] that an expert witness is not always required.
   Att[orney] did an excellent job impeaching Suckow based
   on whether or not there was a valid diagnosis of conduct
   disorder, but was unable by using cross, to bring in the
   key issue of the prior diagnosis of adjustment disorder—a
   diagnosis that would disqualify for dang[erous] off[ender].
   Dr. Cooley would have added facts that were not flattering
   to pet[itioner] but that could have been explained by the
   adj[ustment] disorder diagnosis. That diagnosis would also
   allow att[orney] to bring in details of pet[itioner’s] upbring-
   ing that were relevant and unknown to Suckow. That diag-
   nosis might well lead a court to impose a maximum guide-
   line sentence but would not have, if believed by the jury,
   have allowed a d[angerous] o[ffender] sentence.
D.  The Court of Appeals Opinion
	        The state appealed the judgment of the post-
conviction court. In affirming, the Court of Appeals agreed
with the post-conviction court that “counsel made his deci-
sion to challenge Suckow’s testimony solely through cross-
examination without properly investigating alternative
defense strategies.” Richardson, 277 Or App at 626.
	        The Court of Appeals also concluded that petitioner
had been prejudiced by his counsel’s failure to properly
investigate, including consulting an expert in psychology.
Significantly, the court explained, that failure led to defense
254	                                              Richardson v. Belleque

counsel’s ignorance concerning petitioner’s psychological
diagnosis when he was a boy:
    	“The post-conviction court expressly found that, although
    counsel ‘did an excellent job impeaching Suckow,’ he was
    ‘unable by using cross, to bring in the key issue of the
    prior diagnosis of adjustment disorder[.]’ That finding is
    supported by the evidence, and thus we are bound by it.
    Montez [v. Czerniak, 355 Or 1, 8, 322 P3d 487, adh’d to
    as modified on recons, 355 Or 598, 330 P3d 595 (2014)].
    Like Suckow, counsel did not possess petitioner’s juvenile
    mental health records from St. Mary’s, which revealed that
    petitioner had been diagnosed with an adjustment disor-
    der prior to age 15. During cross-examination, counsel did
    not question Suckow about adjustment disorders or ask
    Suckow whether the evidence suggested that petitioner
    suffered from an adjustment disorder rather than a con-
    duct disorder. Thus, although counsel was able to challenge
    Suckow’s diagnosis by highlighting a lack of evidence of
    a conduct disorder prior to age 15, he was unable during
    cross-examination to elicit testimony that petitioner might
    actually have suffered from an adjustment disorder.”

Id. at 627-28.
	        The Court of Appeals concluded that it was likely
that the jury had relied on Suckow’s diagnosis of petitioner
as having a conduct disorder instead of an “adjustment dis-
order” before the age of 15, and then it turned to the DSM-
IV-TR’s definition of “Adjustment Disorder.”9 As part of its
analysis of prejudice, the Court of Appeals implicitly con-
cluded that defense counsel might have called a psychologist
like Cooley to testify and then reasoned that a jury hearing
the testimony could have found in petitioner’s favor:
    “Had the jury accepted Cooley’s testimony over Suckow’s, it
    could have found that a diagnosis of an antisocial person-
    ality disorder was unavailable. In that case, the jury might
    not have found that petitioner had a ‘severe personality dis-
    order indicating a propensity toward crimes that seriously

	9
        The Court of Appeals did not explain why it considered petitioner’s diagno-
sis from 1965, an “adjustment reaction of early adolescence with behavior distur-
bance, severe,” to be identical to an “adjustment disorder” as defined in the DSM-
IV-TR, which was published many decades later. However, Cooley had referred to
the 1965 diagnosis as an “adjustment disorder” in his report.
Cite as 362 Or 236 (2017)	255

   endanger the life or safety of another’ or that petitioner’s
   mental health rendered him a dangerous offender.”
Id. at 629.
                        II. ANALYSIS
	        A petitioner seeking post-conviction relief based on
inadequate assistance of counsel in violation of the right to
adequate counsel derived from Article I, section 11, of the
Oregon Constitution, “must prove that his or her trial coun-
sel failed to exercise reasonable professional skill and judg-
ment and that, because of that failure, the petitioner suf-
fered prejudice.” Pereida-Alba v. Coursey, 356 Or 654, 661,
342 P3d 70 (2015). We conclude that petitioner proved both
deficient performance by defense counsel and prejudice as a
result.
A.  Defense Counsel’s Failure to Investigate
	        This court has recently had the opportunity to
explore the issue of inadequate assistance of counsel with
respect to a failure to investigate expert testimony in Johnson
v. Premo, 361 Or 688, 399 P3d 431 (2017). In that case, we
concluded that a defense team’s failure to adequately inves-
tigate the client’s version of the facts and to seek additional
forensic data about the cause of the victim’s death consti-
tuted ineffective assistance of counsel. As explained below,
the post-conviction court’s and the Court of Appeals’ conclu-
sions that counsel in this case failed to conduct an adequate
investigation comports with our conclusion in Johnson.
	        As we explained in Johnson, when a petitioner
seeks to establish that counsel failed to exercise reasonable
skill and judgment, what constitutes adequate performance
is fact-specific and dependent on the “nature and complexity
of the case.” 361 Or at 701; Krummacher v. Gierloff, 290 Or
867, 873, 627 P2d 458 (1981). We further stated in Johnson
that
   “the test for adequacy of assistance of counsel ‘allows for
   tactical choices that backfire, because, by their nature,
   trials often involve risk.’ Krummacher, 290 Or at 876. ‘[I]f
   counsel exercises reasonable professional skill and judg-
   ment, a reviewing court will not second-guess the lawyer
   in the name of the constitution, but neither will the court
256	                                   Richardson v. Belleque

   ignore decisions made in the conduct of the defense which
   reflect an absence or suspension of professional skill and
   judgment.’ Id. at 875-76.”
Johnson, 361 Or at 702 (brackets in original). Tactical deci-
sions, we explained, must be based on “a reasonable inves-
tigation.” Id. at 703. At the same time, we recognized an
exception to that rule: “when counsel has ‘reason to believe
that pursuing certain investigations would be fruitless or
even harmful, counsel’s failure to pursue those investiga-
tions may not later be challenged as unreasonable.’ ” Id. at
709 (quoting Strickland v. Washington, 466 US 668, 691, 104
S Ct 2052, 80 L Ed 2d 674 (1984)). Ultimately, we held that
the petitioner’s defense counsel in Johnson rendered inade-
quate assistance when they failed to investigate a defense
theory suggested by their client’s account of events before
they adopted a “wrong venue” defense that was “at best mar-
ginally viable in the guilt phase” and that “lacked any tacti-
cal value in the penalty phase.” 361 Or at 710.
	        Our holding in Johnson is consistent with other
“failure to investigate” cases decided by both this court and
the United States Supreme Court. In Lichau v. Baldwin, 333
Or 350, 360, 39 P3d 851 (2002), for example, the petitioner
contended that his lawyer’s decision to withdraw an alibi
defense was “not supported by an investigation of poten-
tial alibi witnesses and military records that was reason-
able under the circumstances.” After reviewing the limited
investigation the lawyer undertook despite knowledge that
should have prompted further investigation, this court con-
cluded that the lawyer had rendered inadequate assistance.
Id. at 361. As the court explained, “each decision to limit
investigation of a particular defense itself must be a reason-
able exercise of professional skill and judgment under the
circumstances.” Id. at 360.
	        Similarly, in Wiggins v. Smith, 539 US 510, 523, 123
S Ct 2527, 156 L Ed 2d 471 (2003), a case in which the peti-
tioner had been denied post-conviction relief on the ground
that his lawyers had made a tactical decision not to inves-
tigate his life history beyond reviewing two sets of records,
the Supreme Court described the issue as “whether the
investigation supporting counsel’s decision not to introduce
Cite as 362 Or 236 (2017)	257

mitigating evidence of Wiggins’ background was itself rea-
sonable.” (Emphasis in original.) The Court concluded that
the lawyers had “abandoned their investigation of peti-
tioner’s background after having acquired only a rudimen-
tary knowledge of his history from a narrow set of sources”
and that, after review, reasonably competent counsel would
have pursued leads suggested by those records as a neces-
sary predicate “to making an informed choice among possi-
ble defenses.” Id. at 525-26; accord Williams v. Taylor, 529
US 362, 396-97, 120 S Ct 1495, 146 L Ed 2d 389 (2000) (in a
capital-sentence case dependent on a finding of future dan-
gerousness, holding that, in failing to investigate and dis-
cover juvenile, social services, and prison records showing
that the defendant was abused as a child, his limited intel-
lectual ability, and his cooperative, nonviolent behavior in
prison, trial counsel did not make a justifiable tactical deci-
sion to focus on the defendant’s voluntary confession and did
not fulfill their obligation to conduct a thorough background
investigation).
	        To address the adequacy of defense counsel’s
investigation in this case, we must understand the nature
and complexity of the issues presented by the dangerous-
offender hearing. Johnson, 361 Or at 701; Krummacher,
290 Or at 873. First, the stakes for petitioner were high
because of the possibility of a greatly enhanced sentence if
he were found to be a dangerous offender who suffers from a
severe personality disorder with a propensity toward crim-
inal activity. Second, defense counsel knew that the jury
had already heard evidence during the guilt phase of the
trial concerning petitioner’s extensive criminal history, his
troubled early home life, and his confinement in numerous
correctional institutions both as a child and as an adult.
Third, defense counsel knew that a jury would decide the
matter after hearing from a court-appointed psychiatrist
who would testify adversely to petitioner, having diagnosed
petitioner with an antisocial personality disorder. Fourth,
defense counsel knew that the expert’s diagnosis was based
in significant part on interpretation of petitioner’s juvenile
history but that the expert’s diagnosis was insufficiently
supported by the historical information contained in the
expert’s report.
258	                                  Richardson v. Belleque

	         Petitioner alleged that defense counsel had “failed
to conduct an investigation to support his decision not to
obtain a defense psychological evaluation of petitioner to
rebut testimony by prosecution expert, Dr. George Suckow,
that petitioner suffered from an antisocial personality disor-
der.” In light of the nature and complexity of the dangerous-
offender sentencing proceeding and the information that
defense counsel knew, we agree that defense counsel’s deci-
sion not to investigate petitioner’s background as a juve-
nile was not a reasonable exercise of professional skill and
judgment. Defense counsel realized that Suckow would rely
on petitioner’s background as a juvenile to conclude that
petitioner had a conduct disorder before age 15 as part of
his diagnosis that petitioner had an antisocial personality
disorder. Yet defense counsel decided not to further inves-
tigate petitioner’s juvenile background—such as securing a
copy of petitioner’s records at St. Mary’s School for Boys—
even though defense counsel was aware that petitioner had
had a rough childhood and had been repeatedly exposed to
domestic violence at home. To state it another way, defense
counsel knew that the state would call Suckow to testify
that petitioner suffers from an antisocial personality disor-
der, indicating a propensity toward criminal activity, when
neither defense counsel nor Suckow had obtained sufficient
information about petitioner’s history pertinent to that
diagnosis. The record does not reflect that defense counsel
even attempted to obtain additional data about petitioner’s
juvenile history to determine the accuracy or inaccuracy of
the historical information provided by Suckow. We conclude
that defense counsel’s knowledge would lead a reasonable
attorney to investigate the client’s juvenile history further
to prepare for a hearing at which the client was exposed to a
markedly enhanced sentence as a dangerous offender.
	         We also conclude, in light of the nature and complex-
ity of the dangerous-offender sentencing proceeding and the
information that defense counsel knew, that defense coun-
sel’s decision not to consult an expert concerning Suckow’s
diagnosis of petitioner was not a reasonable exercise of
professional skill and judgment. Although the state urges
that defense counsel reasonably pursued a strategy of cross-
examining Suckow to poke holes in Suckow’s diagnosis,
Cite as 362 Or 236 (2017)	259

defense counsel’s choice not to obtain the assistance of a
defense psychologist to address Suckow’s evaluation was
not an informed one. As the Supreme Court observed in
Wiggins, when assessing the reasonableness of counsel’s
investigation, “a court must consider not only the quantum
of evidence already known to counsel, but also whether the
known evidence would lead a reasonable attorney to investi-
gate further.” 539 US at 527.
	In State v. Huntley, 302 Or 418, 730 P2d 1234 (1986),
this court considered the relationship between expert tes-
timony at a dangerous-offender proceeding and the requi-
site finding of fact that an offender suffered from a “severe
personality disorder,” as that term is used in ORS 161.725
(1987). Although the court concluded that the expert’s role
is not to make the ultimate legal determination concerning
the appropriate sentence for a defendant, Huntley, 302 Or at
426, and both the instructions and arguments to the jury
in this case tracked the rule of law announced in Huntley,
the jury nevertheless heard Suckow’s testimony that he had
diagnosed petitioner with an antisocial personality disor-
der and his opinion that petitioner suffered from a severe
personality disorder indicating a propensity toward crimes
that seriously endanger the life or safety of others. Under
Huntley, the jury was expected to “make[ ] a common-sense
decision based on as much relevant information as possi-
ble,” 302 Or at 426, but that is far from a simple task when
it involves evaluation of essentially the entire life of an
offender, in addition to data provided by an expert psychol-
ogist or psychiatrist pursuant to ORS 161.735(3). Moreover,
as we have explained in the past, when expert testimony is
introduced on a subject, there can be a danger that the jury
“may be overly impressed or prejudiced by a perhaps mis-
placed aura of reliability or validity of the evidence,” thereby
leading the jury “to abdicate its role of critical assessment.”
State v. Brown, 297 Or 404, 439, 687 P2d 751 (1984).
	        That is particularly true in this case, when defense
counsel had identified a significant flaw in Suckow’s written
evaluation of petitioner. As counsel’s cross-examination of
Suckow made abundantly clear, Suckow’s report, which had
been prepared after only a single meeting with petitioner
and without the benefit of any psychological testing, did not
260	                                 Richardson v. Belleque

contain enough data about petitioner’s early life to defini-
tively establish that there was “evidence of conduct disorder
with onset before age 15 years,” as required for a diagno-
sis of antisocial personality disorder. See 362 Or at 244 n 5.
But this record contains no adequate explanation as to why
defense counsel did not undertake further investigation to
develop the theory that Suckow’s diagnosis was incorrect
and based on insufficient evidence. As noted above, counsel
merely said that he believed that sometimes, in the minority
of his cases, he found that it was preferable not to intro-
duce expert testimony, because he could “make better hay”
with what the state presented rather than “confusing things
by having my own expert.” That, however, does not explain
why defense counsel did not at least consult with an expert
about the apparent weakness in Suckow’s diagnosis and its
unreliability. As the post-conviction court found, defense
counsel was unaware that petitioner had been diagnosed as
a youth with an adjustment reactive disorder and counsel
was unable to establish on cross-examination that, in light
of that information, (1) petitioner’s behavior as a juvenile
should be viewed “through a totally different diagnosis” and
could be explained by adjustment reactive disorder after
abuse and other conditions petitioner had suffered at home
and (2) Suckow’s diagnosis of antisocial personality disorder
was wrong.
	        Of course, not every failure to investigate infor-
mation that could support a viable defense strategy will
ultimately be deemed inadequate assistance of counsel. In
Strickland, the Court addressed the question of when it
was permissible for counsel to curtail an investigation into
a client’s mental health. The Court observed that strategic
choices made after “thorough investigation of law and facts
relevant to plausible options” do not constitute ineffective
assistance of counsel, but strategic choices “made after less
than complete investigation” may be reasonable only “pre-
cisely to the extent that reasonable professional judgments
support the limitations on investigation.” Strickland, 466 US
at 690-91. Although Strickland concerned a death penalty
trial and penalty-phase mitigation evidence, the context is
similar enough to dangerous-offender sentencing that the
case provides some guidance here.
Cite as 362 Or 236 (2017)	261

	In Strickland, the trial attorney represented a cli-
ent (the respondent) who confessed to multiple murders and
other offenses and who pleaded guilty. During the plea col-
loquy, the respondent told the judge that he had no signifi-
cant criminal record and that he had committed the crimes
due to the stress caused by his inability to support his fam-
ily. The judge indicated that he respected people who took
responsibility for their crimes. Id. at 672. The respondent
waived his right to a sentencing jury, and, in preparing for
the sentencing hearing before the judge, the trial attorney
did not seek out character witnesses or obtain a psychologi-
cal evaluation and instead concluded that “it was advisable
to rely on the plea colloquy for evidence about respondent’s
background and about his claim of emotional stress.” Id. at
673. The trial attorney knew that the respondent, despite
his claim otherwise at the plea hearing, had an extensive
criminal record. The trial attorney also had not observed
the respondent to have any psychological problems, and a
pre-plea psychological report indicated that the client had
no major mental illness or extreme emotional disturbance.
Id. at 673, 676. By limiting the evidence on which he relied
at sentencing, the trial attorney successfully kept out evi-
dence of his client’s criminal record as well as the psycholog-
ical report. Id. at 673-74. The court nonetheless sentenced
the respondent to death, and the respondent subsequently
asserted that he had received inadequate assistance of coun-
sel based on a failure to adequately investigate mitigating
evidence and to obtain additional psychological evidence. Id.
at 675.
	         The Court rejected the respondent’s arguments.
The Court indicated that, when facts supporting a poten-
tial line of defense are known to defense counsel, “the need
for further investigation may be considerably diminished
or eliminated altogether.” 466 US at 691. Ultimately, the
Court concluded that counsel had made a reasonable stra-
tegic choice “to argue for the extreme emotional distress
mitigating circumstance and to rely as fully as possible on
respondent’s acceptance of responsibility for his crimes.” Id.
at 699. The Court observed that restricting character testi-
mony to what came in at the plea hearing “ensured that con-
trary character and psychological evidence and respondent’s
262	                                   Richardson v. Belleque

criminal history, which counsel had successfully moved to
exclude, would not come in.” Id. Thus, the Court concluded,
counsel had exercised reasonable professional judgment in
preparing for the sentencing hearing.
	        The present case bears some similarity to Strickland,
but in a critical respect is different from that case. A bit like
the trial attorney in Strickland who relied on gaps in the
facts of record, counsel in this case had a sentencing strat-
egy that depended, in part, on pointing out gaps in the infor-
mation about his client’s history that Suckow used to arrive
at a diagnosis. There is, however, a significant difference
between this case and Strickland.
	In Strickland, the trial attorney made his decision to
forego presenting the psychological evidence because he had
determined—based on facts known to him from his client and
from a prior psychological report—what the drawbacks would
be to presenting such evidence. Here, by contrast, no evidence
was presented that indicated that counsel knew whether pur-
suit of additional information about petitioner’s juvenile his-
tory would undermine or assist his defense strategy. There is
no indication that the additional information from petitioner’s
St. Mary’s records was already known to defense counsel
when he decided to only cross-examine Suckow.
	        Thus, although defense counsel asserted that he
had made a calculated strategic decision that this was one
of the minority of cases in which it was preferable not to rely
on a defense expert, he did so without adequate knowledge
of the underlying facts. To be a reasonable exercise of pro-
fessional skill and judgment, a lawyer’s strategic decisions
“must be grounded on a reasonable investigation.” Gorham
v. Thompson, 322 Or 560, 567, 34 P3d 161 (2001). In sum,
adequate counsel in this situation would have gained fur-
ther information about petitioner’s psychological conditions
and juvenile history and consulted with a defense expert
in the field of psychology to determine how best to counter
Suckow’s evidence that petitioner suffered from an anti-
social personality disorder.
B.  Prejudice to Petitioner
	        That conclusion, however, does not end our inquiry.
The remaining question is whether petitioner has established
Cite as 362 Or 236 (2017)	263

that defense counsel’s deficient performance prejudiced him.
Trujillo v. Maass, 312 Or 431, 435, 822 P2d 703 (1991).

	        This case presents an opportunity to examine an
issue that we had little occasion to address in Johnson: the
nature of the test to be applied to establish prejudice in a
“failure to investigate” case under Oregon law. Petitioner
contends that Oregon law does not require proof of proba-
ble, more-likely-than-not, prejudice and that he has met the
Oregon standard of prejudice articulated in cases such as
Krummacher, 290 Or at 883, and Stevens v. State of Oregon,
322 Or 101, 110, 902 P2d 1137 (1995): proof that the defi-
cient performance had “a tendency to affect the result of the
prosecution.” Using the federal formulation of prejudice, the
state argues that petitioner was required to prove that (1) it
was “reasonably probable” that competent defense counsel,
after conducting an adequate investigation and consult-
ing an expert, would have presented the testimony of that
expert at trial and (2) it was also “reasonably probable” that,
with that testimony, the outcome of the hearing would have
been different. The state argues that petitioner failed to
meet that test.

	         We begin with the proper formulation of prejudice
under Oregon law. The state is correct that the federal for-
mulation of prejudice in a case like this one requires the
petitioner to prove “a reasonable probability that, but for
counsel’s unprofessional errors, the result of the proceeding
would have been different,” that is, a “probability sufficient
to undermine confidence in the outcome.” Strickland, 466
US at 694. But to the extent the state suggests that peti-
tioner was required to establish prejudice by a probability,
or on a more-likely-than-not basis, we have rejected that
standard. As this court explained several years ago in Green
v. Franke, 357 Or 301, 322, 350 P3d 188 (2015), “where the
effect of inadequate assistance of counsel on the outcome of
a jury trial is at issue, it is inappropriate to use a ‘probabil-
ity’ standard for assessing prejudice.” This court indicated
that, “because many different factors can affect the outcome
of a jury trial, in that setting, the tendency to affect the
outcome standard demands more than mere possibility, but
less than probability.” Id. (emphasis added). Although Green
264	                                              Richardson v. Belleque

concerned a jury’s guilt-phase determination, the same is
true when we are assessing prejudice in a case involving a
jury deciding a sentencing issue.
	        The more difficult aspect of the prejudice prong is
how to apply the “tendency to affect the outcome” test when
criminal defense counsel has failed to adequately investi-
gate before proceeding with a course of action at a hearing.
The parties and amicus curiae Oregon Criminal Defense
Lawyers Association differ on their approach to application
of the test.
	        The state argues that the analysis of prejudice
focuses on the ultimate effect on the jury’s determination
and, therefore, ought to include a “preliminary step” for a
petitioner’s proof involving an objective test: proof that “it is
reasonably probable that a competent attorney would have
presented the evidence” that would have been uncovered
through an adequate investigation. In this case, the state
contends, competent defense counsel would not have chosen
to use the information from Cooley’s report because it would
have undercut the cross-examination strategy and added
factual information that would have supported Suckow’s
testimony that petitioner suffered from a conduct disorder
before age 15.
	        In contrast, petitioner and amicus argue that
adopting the state’s “preliminary step” would change the
prejudice analysis in post-conviction relief cases. Petitioner
argues that the Oregon test is “intentionally general” so as
to cover the myriad ways that an inadequate investigation
can have an impact on the outcome, and he assumes that
defense counsel may well have used the information from
Cooley’s report in arguing that it would have had a tendency
to affect the outcome of the proceeding. Amicus argues that
the force of this court’s decision in Green requires us to reject
the “preliminary step” argument and proposed test.10
	10
        Petitioner also contends that the state raises its “preliminary step” argu-
ment for the first time on appeal, to his detriment. He argues that, had he known
of the argument, he could have provided proof that reasonable trial counsel at the
time would have used the information at the hearing, for example, by seeking an
admission from Jagger or else retaining an attorney expert to testify in the post-
conviction court. Because the state questioned whether competent counsel would
Cite as 362 Or 236 (2017)	265

	        This court’s decision in Green suggests the answer
in this case. In Green, 357 Or at 321, the court noted that
Krummacher, which first used the phrase “tendency to
affect the result,” was referring to the result of the prosecu-
tion being affected by counsel’s failure to object to a ques-
tion. The court then noted that in Stevens, the court had
framed the inquiry in terms of a tendency to affect the out-
come of the trial, when counsel had failed to investigate and
discover witnesses who would impeach the complainant’s
credibility. Green, 357 Or at 322. Thus, the state is correct
that the “tendency to affect the outcome” standard involves
the ultimate outcome of the proceedings as to which coun-
sel’s deficient performance related—in this case, at least,
the jury’s determination that petitioner was a dangerous
offender.
	        Nevertheless, in our view, the state’s argument that
petitioner had to establish a reasonable probability that com-
petent counsel would put on an expert like Cooley to testify
is wrong on two levels. First, by suggesting that petitioner
had a higher bar than proof by “more than mere possibility,”
the state does not give Green its due. In Green, this court
explained that when a jury determination is involved, it is
“inappropriate to use a ‘probability’ standard for assessing
prejudice.” 357 Or at 322. Rather, the “tendency to affect the
outcome” standard “demands more than mere possibility,
but less than probability.”
	        Second, and more importantly, the state’s argument
puts petitioner’s prejudice case in a figurative box, limiting
the analysis of impact to whether reasonable defense coun-
sel would have first called Cooley to testify as to the contents
of his report. Although the state contends that that is solely
how petitioner litigated his case in the post-conviction court
and defended that court’s judgment on appeal, we disagree.
	        In the post-conviction court, petitioner alleged
that defense counsel “failed to conduct an investigation to
support his decision not to obtain a defense psychological
evaluation of petitioner,” “failed to retain a defense psychol-
ogist,” and failed to rebut Suckow’s testimony by a “defense

have used the Cooley information with respect to proof of the inadequate perfor-
mance prong, petitioner’s argument concerning detriment is not well taken.
266	                                  Richardson v. Belleque

psychologist” who “would have provided testimony that peti-
tioner does not meet the diagnostic criteria for an antisocial
personality disorder and that petitioner did not suffer from
a severe personality disorder.” He alleged that, as “a result
of counsel’s failure to retain a defense psychologist,” the
jury “relied exclusively upon the testimony of Dr. Suckow to
determine that petitioner did suffer from a severe personal-
ity disorder.” In oral argument to the post-conviction court,
petitioner’s attorney argued that it was “clear from the tran-
scripts” that defense counsel had failed to “retain an expert
witness” and that “his rationale” for failing to do so “doesn’t
hold water.” He argued that problems “Suckow had attributed
to a conduct disorder, were actually a reaction disorder from
severe abuse that [petitioner] had suffered as a child” and
that Suckow had not considered the records from St. Mary’s.
Petitioner’s attorney also argued that defense counsel,
although he tried, could not move Suckow off his diagno-
sis of petitioner, but that “evidence was available * * * that
he could have presented through an expert that would have
established that [petitioner] didn’t qualify for an antisocial
personality disorder diagnosis.” Similarly, in the Court of
Appeals, petitioner’s lawyer argued three different theories
of deficient performance in briefing: (1) defense counsel was
ineffective “because he did not investigate and obtain peti-
tioner’s ‘juvenile records from St. Mary’s that contain[ed]
a diagnosis of adjustment reactive disorder’ ” (quoting the
post-conviction court); (2) defense counsel was ineffective by
failing to consult with an expert, who “ ‘would have obtained
and reviewed historical records’ ” (quoting Cooley’s report);
and (3) defense counsel was ineffective by failing to call an
expert to testify at the dangerous-offender hearing.
	        Based on the record, we reject the state’s argument,
and we credit arguments by petitioner and amicus that it
was more than a mere possibility that competent defense
counsel could have used the information from Cooley’s report
in ways that “could have tended to affect” the outcome of the
dangerous-offender hearing. Green, 357 Or at 323; Lichau,
333 Or at 365. As we have noted, “many different factors
can affect the outcome” of a case. Green, 357 Or at 322. On
this record, had counsel adequately investigated petitioner’s
past and consulted a psychological expert, he would have
Cite as 362 Or 236 (2017)	267

obtained petitioner’s juvenile mental health records and
would have learned that the expert could provide ammu-
nition to oppose an enhanced dangerous-offender sentence:
(1) an opinion critical of Suckow for failing to obtain and
review petitioner’s records as a juvenile to support his
diagnosis; (2) mitigation evidence that petitioner had been
abused by his mother; (3) hard evidence that petitioner did
not have a conduct disorder as a youth—a diagnosis by a
psychiatrist that petitioner had an adjustment reaction of
early adolescence; and (4) an opinion rebutting the antici-
pated testimony from Suckow that petitioner suffered from
an antisocial personality disorder.
	        And on this record, there was “more than a mere
possibility” that counsel could have used that information
in cross-examining Suckow or by calling that expert to the
stand or doing both. Competent counsel could have used
Suckow’s failure to obtain the St. Mary’s records or other
additional data to show that Suckow had not been thor-
ough in reaching his opinion. Competent counsel also could
have confronted Suckow with the diagnosis by psychiatrist
Johnson that petitioner had an adjustment reaction of early
adolescence, without necessarily calling a defense expert
witness, to shut down Suckow’s explanation to the jury that
there was indirect evidence that petitioner had a conduct
disorder before age 15. Competent counsel also could have
presented a defense expert’s testimony, to provide the jury
with the information that counsel would have learned upon
investigation and consultation, including a direct rebuttal of
Suckow’s diagnosis and an explanation of petitioner’s con-
duct that was not as damaging as an antisocial personality
disorder.11
	        Given the uses to which counsel could put the infor-
mation from the Cooley report, there was more than a mere
possibility that the jury could have rejected the state’s con-
tention that petitioner suffered from a “severe personality
	11
        And, petitioner adds, even apart from using the information at the hear-
ing, competent counsel could have used the information gained from Cooley to
try to avoid a dangerous-offender hearing at all and to gain advantage in peti-
tioner’s sentencing. For example, he argues, competent counsel might have first
attempted to persuade Suckow and the prosecutor to change their minds about
petitioner’s diagnosis and to negotiate with the prosecutor for a different sen-
tence for petitioner before the scheduled hearing.
268	                                 Richardson v. Belleque

disorder.” First, as our discussion above of the Huntley case
and the jury instructions demonstrate, the jury fully under-
stood that it was not bound by any expert testimony about
diagnoses—including Suckow’s testimony. Second, Cooley
opined in the post-conviction proceeding that Suckow could
not legitimately have made a diagnosis of an antisocial per-
sonality disorder on the facts presented and that petitioner
did not have an antisocial personality disorder. As described
above, although the St. Mary’s records contained additional
information about petitioner’s history of truancy, running
away from home, fighting, and stealing, all of that informa-
tion was explained by Cooley as being consistent with adjust-
ment disorder in light of petitioner’s life as a child, given
the abuse in his home. Had the jury heard testimony from
an expert like Cooley, it may well have doubted the diag-
nosis of an antisocial personality disorder and whether the
state had proved, beyond a reasonable doubt, that petitioner
suffered from a severe personality disorder. See Apprendi
v. New Jersey, 530 US 466, 490, 120 S Ct 2348, 147 L Ed
2d 435 (2000) (“Other than the fact of a prior conviction,
any fact that increases the penalty for a crime beyond the
prescribed statutory maximum must be submitted to a jury,
and proved beyond a reasonable doubt.”). Accordingly, we
conclude that there was more than a mere possibility that
counsel’s failure to investigate petitioner’s past and consult
with a defense expert about Suckow’s expert report could
have tended to affect the outcome of the dangerous-offender
proceeding.
	       The decision of the Court of Appeals and the judg-
ment of the circuit court are affirmed.
