1. the Dirty Dozen_12 Sources of Bias in Forensic Neuropsych... (by Richards Geiger Tussey)

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The Dirty Dozen: 12 Sources of Bias in Forensic
Neuropsychology with Ways to Mitigate
ARTICLE in PSYCHOLOGICAL INJURY AND LAW · OCTOBER 2015
DOI: 10.1007/s12207-015-9235-1

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Psychol. Inj. and Law (2015) 8:265–280
DOI 10.1007/s12207-015-9235-1

The Dirty Dozen: 12 Sources of Bias in Forensic Neuropsychology
with Ways to Mitigate
Paul M. Richards 1 & Jennifer A. Geiger 1 & Chriscelyn M. Tussey 2

Received: 10 September 2015 / Accepted: 16 October 2015 / Published online: 31 October 2015
# Springer Science+Business Media New York 2015

Abstract The ever expanding role of a forensic neuropsychologist in civil litigation has rightfully led to a higher level
of expectation for this expert, in realms such as clinical and
courtroom knowledge, objectivity, and work product utility.
The onus is on forensic neuropsychologists to ensure that
these expectations are met. Recognizing that bias is inherent
in clinical and forensic work, it is imperative that in high
stakes situations such as forensic neuropsychological assessment, the evaluator is proactively conscientious in recognizing, and minimizing, the effects of these biases. This article
highlights 12, of many, common biases about which the prudent forensic neuropsychologist should always be mindful of,
during evaluation as well as the provision of deposition or trial
testimony. Role, cognitive, and practice biases are defined and
illustrated with examples. Specific suggestions are extracted
from both empirical literature and forensic experience on how
to recognize and mitigate these biases. The information
contained in this article is intended to provide sound and practical strategies that can be useful for forensic neuropsychological practitioners. Attorneys will also find the content useful
when working with such experts, including during deposition
and cross examination preparation.

Keywords Forensic neuropsychology . Civil litigation .
Testimony . Neuropsychological assessment . Expert witness .
Cognitive bias . Confirmation bias
* Paul M. Richards
[email protected]
1

Independent Practice, Louisville/Denver, CO, USA

2

Independent Practice, New York University School of Medicine/
Bellevue Hospital Center, New York, NY, USA

Introduction
The field of forensic neuropsychology has proliferated for
more than two decades with continued growth expected in
the foreseeable future (Kaufmann, 2009; Kaufmann &
Greiffenstein, 2013). This time period has seen publication
of numerous edited books on this topic (Boone, 2013;
Heilbronner, 2008; Horton & Hartlage, 2010; Larrabee,
2005, 2012; McCaffrey, Williams, Fisher, & Laing, 2004;
Sweet, 1999; Young, Kopelman, & Gudjonsson, 2009).
Sweet, King, Malina, Bergman, and Simmons (2002) documented the Bprominence^ of forensic neuropsychology vis-àvis an increasing number of peer-reviewed journal articles and
continuing education opportunities at national conferences on
this topic. Sweet, Meyer, Nelson, and Moberg (2011) reported
that approximately 72 % of surveyed neuropsychologists provide forensic evaluations and consultation services.
Greiffenstein and Kaufmann (2012) recently concluded
BGrowth in forensic consulting for neuropsychology is
outpacing every related brain-behavior expertise and the
growth is accelerating^ (p.14).
Neuropsychologists are increasingly retained or
subpoenaed to provide forensic and clinical opinions related
to diagnosis, prognosis, causality, and permanency regarding
individuals with a host of compensable conditions such as
traumatic brain injury, anesthesia/surgical accidents, carbon
monoxide poisoning/toxic exposure, and post-traumatic stress
disorder (Richards & Tussey, 2013). Similar to expert witnesses in any field, the forensic neuropsychologist must strive
to be objective and unbiased to maximize effectiveness and
credibility. Triers of fact (i.e., judge, jury, and arbiter) will
likely discount or ignore the testimony of those experts who
are perceived as biased, advocates for one side or the other, or
have their own personal, financial, or political agenda to promote. Skilled attorneys will probe for bias during deposition

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and seize every opportunity to expose the opposing neuropsychologist’s bias in trial which can prove pivotal in the eyes of
judge and/or jury and influential in judgment. In this Bage of
the internet,^ even a cursory online search reveals articles
such as BExposing An Expert Witness’ Bias During Cross
Examination: Collateral Attack^ in which Rubinowitz and
Torgan (2013) offer a step by step guide with specific questions to demonstrate bias and thereby discredit the expert witness. Quite simply, not only does the effective forensic neuropsychologist have to be imminently qualified regarding
education/experience and employ scientific and reliable methodology, he/she must take steps throughout the entire expert
witness process to maintain objectivity and impartiality.
Although each forensic case is different with unique expertexaminee dynamics and differing relationships with the
retaining attorney, there are frequently common threats to objectivity and sources of bias that the seasoned expert sees time
and again.
In this article, we discuss 12 different sources of bias that
the forensic neuropsychologist may encounter in his/her evaluation or provision of expert opinions and testimony. As evident in Appendix 1, the first four biases (role, financial,
referral source, and self-report) are logistical and administrative, pertaining to how the neuropsychologist has set up the
evaluation and the source of information relied upon. The next
two are statistical in nature (under-utilization of base rates and
ignoring normal variance in test scores). The final six biases
might best be described as a subgroup of cognitive, personal,
and attributional biases (confirmation, personal/political,
group attribution, diagnosis momentum, good old days, and
overconfidence). This list is certainly not exhaustive as other
sources of bias exist. Starting 60 years ago with the seminal
work of Meehl and Rosen (1955), researchers in the fields of
social and cognitive psychology as well as behavioral research
have identified, discussed, and studied social, attributional,
cognitive, and experimental biases including ways they might
affect the psychologist’s judgment and decision making process. However, a review of all these biases is beyond the scope
of this article, and instead, we focus on some that are frequently cited in the literature as potentially problematic and that are
topics of interest and study among neuropsychologists at national conferences and workshops. Although there may be
applicability to the criminal arena and with pediatric populations, the biases that follow are discussed primarily within the
context of personal injury civil litigation with an adult population. Other authors (Deidan & Bush, 2002; Martelli, Bush,
& Zasler, 2003) have identified a number of biases and ethical
issues in clinical neuropsychology and listed ways to address;
the present article builds on prior work in this area with a
greater emphasis on forensic practice. We hope that an exploration and review of these issues will promote future discussion and research and thereby improve the objectivity of those
neuropsychologists who choose to provide forensic services

Psychol. Inj. and Law (2015) 8:265–280

or those who unwillingly enter the legal arena (i.e.,
subpoenaed to testify as fact or treating expert). The format
we follow in this article is to first define the potential source of
bias with examples of what can go wrong in such instances
followed by recommendations of ways to mitigate.

Role Bias: Conflating Clinical and Forensic Roles
Clear distinctions exist between clinical and forensic roles
with precautions to not mix these roles (Richards & Wortzel,
2 0 1 5 ; S t r a s b u rg e r, G u t h e i l , & B r o d s k y, 1 9 9 7 ) .
Neuropsychologists routinely receive clinical (non-forensic)
referrals and provide evaluation, treatment, and consultation
services to these patients. The treating neuropsychologist frequently attempts to develop a therapeutic alliance with the
patient which emphasizes trust and empathy and may view
him/herself as an advocate for the patient in order to promote
health, well-being, and recovery. At some point during or after
this process, the neuropsychologist may receive an informal
attorney request or subpoena to provide testimony about a past
or current patient who has been the recipient of clinical services. In this scenario, the neuropsychologist is typically referred to as a Bfact witness^ or Btreating expert.^ It is permissible for this clinician to testify under oath regarding facts
about his/her patient such as start, duration and completion
of care, methods of treatment employed and outcome, working diagnosis, payments received, and so on. However, the
treating neuropsychologist has not performed a forensic evaluation and therefore cannot provide certain expert opinions or
formulate conclusions from the reports of others, and it is
when he/she Bchanges hats^ and provides forensic opinions
regarding causality, permanency of a condition, and other
psycho-legal matters that potential role conflict and/or ethical
issues arise.
In marked contrast, the retained expert has been hired by an
attorney or other third party to evaluate a plaintiff to render
forensic opinions, clearly spelling out the limits of confidentiality before beginning the evaluation with a primary goal of
aiding the legal process. He/she has to conduct an evaluation
that holds up to the scrutiny of the adversarial process that can
include the opposing neuropsychologist’s analysis/critique
and vigorous cross examination. The retained expert has to
meticulously corroborate examinee self- report with collateral
data, never provides treatment to the examinee, and avoids
any perception of advocacy, while attempting throughout this
process to be objective and impartial.
Greenberg and Shuman (1997) listed important differences
between therapeutic and forensic relationships, discussing
how blurring these boundaries lead to Brole conflict^ and
even, BIrreconcilable Conflict.^ These authors distinguished
clinical from forensic roles by noting they typically involve
competing interests that are often at odds. They described the

Psychol. Inj. and Law (2015) 8:265–280

role conflict as that of a dual role, violating ethical principles
established by the American Psychological Association.
Malina, Nelson, and Sweet (2005) concluded that BWriting a
forensic report after providing treatment is consistent with
assuming a dual role with the patient-litigant, and harm to
the therapeutic alliance, or threat to the neuropsychologist’s
objectivity are real possibilities^ (p. 30). Melton, Petrila,
Poythress, and Slobogin (2007) described mental health professionals who serve as the retained expert of a patient previously or currently being treated as a Bdouble agent,^ whereas
Richards and Wortzel (2015) referred to this person as a Bdual
agent.^
The BSpecialty Guidelines for Forensic Psychology^
(American Psychological Association, 2013) addresses
therapeutic-forensic role conflicts in Guideline 4.02.01 as
follows:
Providing forensic and therapeutic psychological services to the same individual or closely related individuals involves multiple relationships that may impair objectivity and/or cause exploitation or other harm. Therefore, when requested or ordered to provide either concurrent or sequential forensic and therapeutic services,
forensic practitioners are encouraged to disclose the potential risk and make reasonable efforts to refer the request to another qualified provider. If referral is not possible, the forensic practitioner is encouraged to consider
the risks and benefits to all parties and to the legal system or entity likely to be impacted, the possibility of
separating each service widely in time, seeking
judicial review and direction, and consulting with
knowledgeable colleagues. When providing both
forensic and therapeutic services, forensic practitioners seek to minimize the potential negative effects of this circumstance (P. 11).
Table 1 below summarizes some of the primary role differences between a fact witness/treating expert and a retained
expert. This list is not exhaustive or exclusive but highlights
some key differences culled from the literature that forensic
neuropsychologists should consider.
Regarding mitigation and avoidance of these situations,
Woody (2009) articulated the ethical issues of Bmultiple roles
in forensic services^ and then strongly recommended that the
psychologist decline or withdraw from one of the roles. More
recently, Brodsky (2013) provided recommendations for how
to best handle situations in which the treating expert is asked
to provide forensic opinions in a report and/or during testimony. We concur with the above authors and posit that the simplest and most appropriate way to avoid potential bias in this
area is for the fact witness or treating expert to not provide
forensic opinions, testifying within the boundaries of what he/
she was hired to do and not conflating roles. When pressed by

267

counsel to do such prior to or during testimony, responses
might be: BI did not conduct the type of evaluation necessary
to answer your question^ or BI conducted a clinical but not
forensic evaluation and therefore, do not have the basis to
form an opinion about what you asked.^ Counsel’s inevitable
follow up questions to these responses afford additional opportunities for the expert’s explanation of the inherent issues.

Financial/Payment Bias
Serving as an expert witness can be complex and stressful for
the neuropsychologist, and what should be the most straightforward component of this process (clear and ethical payment
arrangements) sometimes proves confusing or frankly unethical. We next review the continuum of reimbursement arrangements that vary from straightforward to murky to highly biased. First, it is commonly agreed that accepting a forensic
case based on any form of contingency payment arrangements
(payment of the expert’s fees is contingent on legal outcome)
is inappropriate with an inherent conflict of interest that
should be avoided (Binder et al., 2012; Bush, Connell, &
Denney, 2006). Such practices potentially bias the expert or,
at a minimum, contribute to the perception of bias. Second and
less straightforward than contingency financial arrangements
is a Blien^ that may also be termed a Bletter of protection^
(Woody, 2011). In this instance, the expert signs a lien agreement with the retaining attorney which Bprotects^ his/her balance due and seemingly promises payment for services
rendered when/if the case settles, regardless of the outcome
of the case. This presumably covers those instances in which
the patient does not have the finances, health insurance, or
other resources to cover the costs of neuropsychological services such as evaluation, treatment, and consultation.
However, what initially sounds like a creative way to help
someone who is indigent because of a compensable accident
or condition is fraught with ethical pitfalls as discussed by
Woody (2011) who ultimately discourages the psychologist
from engaging in this practice. The neuropsychologist who
accepts a lien as a potential source of payment has to answer
and defend the inevitable question of: BDoctor, isn’t it true that
eventual payment of your final bill is 100 % dependent on the
outcome of this case?^ Personal injury cases frequently take
years to resolve, and there is no guarantee that the plaintiff will
recover anything let alone the full amount demanded or some
percentage thereof. Even the most principled neuropsychologist has to fight the reality or perception of bias that his/her
testimony is somehow shaded or adjusted to help insure a
successful judgment so that the statement for services rendered is paid in full. Anecdotally, some neuropsychologists
charge interest for past balances which places him or her in
the untenable position of somehow evaluating the probability
of eventually getting paid and then serving as a money lender

268
Table 1

Psychol. Inj. and Law (2015) 8:265–280
Primary role differences between a fact witness/treating expert and a retained expert
Fact witness/Treating expert

Retained expert

1. Who is client

The patient

Retaining attorney; Court

2. Forms doctor–patient relationship

Yes

No

3. Provides treatment & Explains test results
4. Advocates for patient

Yes
Yes

No
No

5. Relies extensively on records and other collateral contacts
6. Services provided within adversarial context

Not Necessarily
No

Yes
Yes

7. Provides forensic opinions on causality & permanency

No

Yes

8. Knowledgeable about facts of legal matter/claims made
9. Fiduciary responsibility to whom

Not necessarily
The patient

Yes
Retaining attorney; Court

10. Professional services paid by whom

The patient and/or insurance company

Retaining attorney; Court

who calculates interest on past due amounts. Whereas
Guideline 5.02 of the SGFP states that: BLetters of protection
…are not considered contingent fees unless payment is dependent on the outcome of the matter,^ we concur with Woody
(2011) that acceptance of a lien/letter of protection poses potential ethical, legal, and business pitfalls and should therefore
be avoided.
The third and most straightforward form of payment is
BFee for Service^ where the neuropsychologist is paid for
his/her time, irrespective of legal outcome. We have previously (Richards & Tussey, 2013) recommended that before providing any forensic services, the neuropsychologist has the
retaining attorney/party sign an Expert Witness Retention
Contract that clearly spells out in a transparent way the expert’s fees including retainer (if any) and duties. Babitsky and
Mangraviti (2005) recommend that experts BGet paid up front.
An expert for the plaintiff who fails to do this may create a de
facto contingent fee situation where the expert is not likely to
be paid unless the plaintiff wins^ (p. 46).
There are, of course, other forms of payment such as pro
bono and sliding fee arrangements, and some disability insurance carriers and IME companies request that the expert’s fees
be Bcapped^ at a set amount. Ultimately, the neuropsychologist has to decide (and perhaps explain during testimony) why
he/she deviated from their standard practice for this one particular case at hand. It is imperative in these scenarios that the
neuropsychologist not Bcut corners^ (e.g., skip some tests, not
review all the relevant records, or prepare insufficiently) because he/she is not compensated or only partially paid.
Providing pro bono services is laudable, but the forensic neuropsychologist must examine his/her subtle and obvious motivations for doing such. Colleagues occasionally provide pro
bono or discounted forensic services out of empathy for
impoverished litigants who have been Bwronged and need
their day in court^ or are trying to establish a reputation early
in their career, practices that might best be saved for the clinical but not forensic arena. Finally, there are Bback door^
referrals in which an attorney asks a treating physician to refer

the patient/plaintiff to a neuropsychologist, hoping an evaluation can be paid by health care insurance or a government
payer such as Medicare or Medicaid. However, most if not
all commercial insurance carriers and government health entities exclude forensic evaluations as they are not medically
necessary. One would certainly have to question the ethics and
potential bias of any neuropsychologist willing to disguise
charges for hours of record review and report writing as clinical rather than forensic.

Referral Source Bias (and Retaining Attorney
Pressure)
Rule 26 of the Federal Rules of Civil Procedure (1975) requires retained experts who are disclosed as witnesses in a
proceeding to submit, among other documents, a list of past
testimony (deposition and trial) over the preceding 4 years.
This disclosure must include case caption, number, and jurisdiction and whether the expert was retained by the plaintiff or
defense; however, there is no requirement to disclose case
outcome or other information. This BRule 26 disclosure^ often
provides fodder for the cross examining attorney to probe for,
insinuate or assert bias based on a preponderance of testimony
for one side or the other. However, the breakdown of where
one’s referrals come from is not indication of bias in and of
itself. As noted by Greiffenstein and Kaufmann (2012), BA
simple ratio of plaintiff to defense cases is not compelling
evidence for objectivity versus partisanship. It is a reality that
a [forensic neuropsychologist’s] career trajectory increasingly
attracts retention by one side or the other. There are many
reasons for this including word of mouth, aggressive versus
conservative neurodiagnostic approaches, and scientist- practitioner ethos versus pure clinical orientation^ (p. 57).
On the other hand, one could easily speculate that a reason
why only plaintiff or defense attorneys will repeatedly or exclusively retain a particular forensic neuropsychologist is because that expert is predictable, tending to consistently proffer

Psychol. Inj. and Law (2015) 8:265–280

opinions that are helpful for that side while hindering the
opposing side’s case. Why would an expert who only accepts
plaintiff or defense cases, and especially those situations in
which one particular attorney or law firm accounts for all or
a majority of referrals, not become jaded over time and gradually conceptualize cases from that standpoint? If the expert is
employing a Bscientific method^ to forensic neuropsychology
as advocated by Larrabee (2012), that person should theoretically be equally conversant and willing to accept both defense
and plaintiff cases, assuming of course ethical payment and
other arrangements were in place.
Lees-Haley (1999) called a 50–50 forensic referral pattern
an B…unfounded but widely circulated myth that testifying
50 % for plaintiff and 50 % defense is evidence of absence of
bias. This myth is a problem in the context of debiasing because it is used to imply lack of bias when ‘50-50’ may actually be evidence of just the opposite. The 50–50 myth is a
classic case of an unexamined proposition that survives by
repetition without critical review^ (p. 14). However, as one's
year's of forensic practice increase, it is difficult and perhaps
unrealistic for the neuropsychologist to maintain a true 50–50
referral pattern, and we are not aware of studies addressing
bias (or lack thereof) with this phenomenon. It may be that the
referral ratio is not as important as a wide referral network,
and, therefore, we concur with Martinez (2014) who noted:
BDiversifying a forensic practice may reduce pressure to satisfy the referral source due to interest in future referrals^ (p. 2).
In summary, it may be common for neuropsychologists who
testify exclusively for one side or the other to get type-cast as
either a Bliberal plaintiff neuropsychologist^ or Bconservative
defense expert.^ However, rather than being concerned about
these labels, it is much more important for the forensic neuropsychologist to guard against automatically offering favorable
opinions for the side that hired them.
Somewhat more problematic than where a neuropsychologist’s forensic referrals come from are more subtle but potent
biasing factors that begin the moment the phone rings with an
attorney referral. At that time, the referring attorney may attempt to have the expert Bjoin the team^ with statements such
as BDoctor, I know you will do your own evaluation but I’m
sure you will find that Mrs. Smith sustained a traumatic brain
injury (or did not).^ These types of statements begin a push to
affiliate with the referring attorney with subtle pressure to
accept their prevailing view. Attorneys by definition are zealous advocates and persuasive not only to judge, jury, and
client but their expert(s) as well. We encourage resisting attorney sweeping case conclusions before the neuropsychologist
reviews all the records and conducts his/her evaluation, setting
appropriate boundaries up front such as: BI appreciate that
information but I’d like to be the judge of whether Mrs.
Smith sustained a brain injury after I complete my
evaluation.^ Information received at the onset of a case should
bring into consideration the long-studied psychological

269

principle of primacy bias or anchoring, that is, early information may lead to premature conclusions that are difficult to
abandon as the case unfolds. The simplest way to counter
potential bias in this area is to limit early attorney meetings.
The focus of the initial attorney-expert contact should primarily be administrative in nature to rule out potential
conflicts of interest, assure competency with the condition in question, and provide fees/policies and other
necessary documents (e.g., expert witness retention
agreement, CV, and disclosure of past testimony).
Post evaluation, attorneys will sometimes ask the neuropsychologist to make report changes that can vary from minor
factual mistakes (incorrectly reporting someone has three siblings when, in fact, it is two) to substantive (changing forensic
opinions about diagnosis or causation). The forensic neuropsychologist should never alter a report that has been finalized, even if it has only been sent to the referring attorney who
promises to shred it. Such requests have to be evaluated according to accuracy and can be accomplished in the form of an
addendum or supplemental report where there is a paper trail
of the neuropsychologist’s decision-making process with full
disclosure. Factual inaccuracies can and should be corrected;
however, requests for more substantive changes have to be
evaluated on a case by case basis. For instance, if additional
key records or facts become available after report completion
and that information changes forensic opinions, an addendum
is the appropriate forum to document using language such as
BAfter reviewing the following records on this date, my opinion of X changes to Y for the following reasons.^ Otherwise,
if the retaining attorney is requesting that an expert alter his/
her report with substantive changes in the absence of new facts
or simply to bolster their legal case, a firm but polite BNo^ is
recommended with explanation that the expert is not willing to
compromise his /her ethics and integrity. Setting this type of
ethical boundary up front communicates the expert’s unwavering conviction he/she cannot be manipulated or bullied
which often paves the way for a more productive working
relationship down the road.
Finally, after a judge or jury has delivered a verdict,
experts are sometimes tempted to call the retaining attorney to find out Bhow did we do^ with maybe a
specific question of Bhow much did the jury award the
plaintiff?^ This communicates an emotional investment
in the outcome that should be avoided. Some experts
may have need for being perceived as the Bstar witness^
in high profile cases or Bhitting a homerun^ with their
testimony which only communicates partisanship.
Moreover, if an expert is that intrigued by a jury verdict, he/she was likely biased from the start and may
have approached the forensic evaluation from the standpoint of winning vs. losing a case or defeating the opposing expert, factors inconsistent with the awareness
and mitigation of bias that we advocate in this article.

270

Self Report Bias (Need for Corroborative Data)
In psychology doctoral training programs and medical school,
the fledgling clinician is typically taught to Blisten to the
patient.^ This admonition also holds true for the forensic neuropsychologist, yet, it must be tempered with a statement
about the critical importance of not relying exclusively or even
extensively on examinee self report, stressing the need to supplement subjective history with a thorough review of
collateral/corroborative information. Along with interview/
mental status exam and neuropsychological test results, a thorough record review helps form the triad of an evidence-based
and scientifically sound forensic evaluation and guideline of
opinions for eventual testimony. In this section, we focus on
the limitations of self-reported subjective history without
judgment or mention as to whether an examinee might be
consciously distorting the history for secondary gain, misremembering pre, and post-injury events, or is simply
amnestic for facts surrounding a particular incident.
Being a plaintiff, defendant, or other interested party in
civil litigation suggests an inherent bias that may place an
emphasis on providing information that leads to the best possible outcome of that legal proceeding. Examinee self-report
in forensic settings can be notoriously unreliable, with problems that bring into question the accuracy of one’s subjective
history. Greiffenstein, Baker, and Johnson-Greene (2002) examined agreement between self-reported and actual academic
performance with groups of litigants, including those with
severe traumatic brain injury and Blate postconcussion
syndrome^ (LPCS). They found that both groups inflated past
academic performance significantly more than non-litigating
controls; however, the magnitude was greater with the LPCS
group. The authors concluded as follows: BThese findings
support previous studies which showed self report is not a
reliable basis for estimation of pre-injury cognitive status.
Retrospective inflation may represent a response shift bias
shaped by an adversarial context rather than a form of
malingering^ (p. 202). Thus, analyzing past academic records,
including transcripts, results of standardized testing, and even
supervisor ratings /employment records are helpful in corroborating reported history. In addition to estimating premorbid
cognitive functioning, records often address pre-incident functioning across an array of psychiatric, neurologic, substance
abuse, and other areas and thus are vital to obtain (if they
exist), review, and incorporate within the overall evaluation
context.
Lees Haley et al. (1997) studied the accuracy of selfreported histories in a large sample of personal injury litigants
in comparison to a non-litigating control group in five regions
throughout the USA. Results showed that the litigants rated
their histories across various cognitive (concentration and
memory), psychiatric (depression, anxiety, and substance
use), and physical (headache and fatigue) domains as well as

Psychol. Inj. and Law (2015) 8:265–280

employment, academic areas, and Blife in general^ to be superior and more trouble free than the non-litigating controls.
Lees Haley et al. (1997) did not believe that malingering
could fully account for the significant differences and offered
social pressures, cognitive dissonance, and other possible explanatory factors. Somewhat related (and discussed in detail
in section 11 of this article) is the Bgood old days^ bias
(Iverson, Lange, Brooks, & Rennison, 2010) in which forensic examinees tend to over-report pre-incident accomplishments and abilities.
That neuropsychologists often evaluate individuals who
legitimately have no memory or have impaired recall of a
compensable traumatic event, such as the examinee with a
history of brain injury including a loss of consciousness and/
or post-traumatic amnesia in which no memories were stored,
also dictates the necessity of reviewing records surrounding
the incident in question. This is especially important when
trying to objectively establish acute injury parameters that
help grade TBI severity or the duration of loss of consciousness (LOC) for the victim of carbon monoxide poisoning. In
such instances, paramedics, first responders, and emergency
physicians who are trained to evaluate and document acute
injury characteristics such as Glasgow Coma Scale scores,
length of post traumatic amnesia, or carboxyhemoglobin
levels provide vital information that Bfill in the blank^ for
the time the examinee has no recall. Hospital or outpatient
provider records help trace an individual’s recovery (or lack
thereof) and often contain neuroimaging reports, treatment
provided and outcome, and cognitive evaluation findings.
It is time saving for the forensic neuropsychologist to have
a checklist of these and all other recommended pre- and postincident records to give to the referral source up front and as a
cross check for the psychologist to ensure no primary source
of records is being over-looked. Many civil personal injury
cases can entail hundreds if not thousands of pages of records;
therefore, developing an organizational system in which records are indexed chronologically or according to provider or
specialty is recommended. However, relying exclusively on
the retaining attorney or claims adjuster to provide all or at
least key records in a case is presumptive as interested parties
sometimes Bcherry pick^ records that support their side, withholding key records harmful to their central premise
(Schatman & Thoman, 2014). The forensic neuropsychologist
should therefore insist that all pre- and post-incident records
be provided including, if necessary, going directly to the
source document (e.g., requesting a vital discharge summary
directly from the hospital). Awareness of a record with important implications that cannot be obtained should be noted in
the report to promote transparency.
Moreover, third party records can sometimes be misleading
and according to Cripe (2002) have significant limitations
including B…limited sampling; varied report writing styles;
indirect methods; narrow focus; subjective biased

Psychol. Inj. and Law (2015) 8:265–280

interpretations; and lack of validation^ (p. 8). Thus, it may be
difficult to determine if the hospital psychologist’s definition
of Bdepression^ is the same as or close to the diagnostic
criteria used by the outpatient psychiatrist or IME physician
all of whom evaluated the same examinee and documented
Bdepression.^ Psychologists sometimes rely on affidavits or
questionnaires that have been completed by an examinee’s
spouse who may also be a party in the lawsuit. Again, the
accuracy of these documents must be scrutinized to rule out
or establish potential response bias.
Finally, the lack of reliability in self reporting has even
been documented in non-litigating normal controls where
there is no injury or apparent secondary gain. For instance,
Otto et al. (1994) studied the effect of depression on memory
functioning. These authors concluded that their findings were
B…consistent with reports indicating that the self-report of
memory complaints is linked to severity of depression but is
not significantly associated with actual memory performance
in elderly subjects^ (p. 86). Thus, the forensic examiner
should be reminded that individuals distort self-report intentionally perhaps to appear more impaired than they actually
are and unknowingly as a function of conditions such as depression. As well, there are situations in which the examinee
genuinely can’t remember or has impaired memory as a result
of loss/alteration of consciousness or other brain-related
condition.

Under-Utilization of Base Rates
The term base rate is defined as the frequency or prevalence
of a diagnosis, condition symptom, sign, or disorder within a
given population. For instance, the base rate of dementia in the
general population over age 85 years is approximately 20 %
whereas the base rate of attention-deficit/hyperactivity disorder in school age children is estimated as 3 to 5 % (American
Psychiatric Association, 1994). Base rates are fundamental in
all of the medical sciences but especially important to the
forensic neuropsychologist given the high number of tests
typically administered. Base rates help inform the decisionmaking process and address the significance of a particular
test finding (McCaffrey, Palav, O’Bryant, & Labarge, 2003).
Base rates are especially important in calculation of positive
predictive probability and negative predictive probability (see
Larrabee, 2012 for definitions and formulas of these classification statistics as well as sensitivity and specificity).
However, there is reason to believe that neuropsychologists
under-utilize or are unaware of base rates. Labarge,
McCaffrey, and Brown (2003) surveyed 279 members of the
National Academy of Neuropsychology, posing various scenarios in which participants had to answer questions related to
calculating sensitivity, specificity, and positive and negative
predictive values. Whereas a majority of neuropsychologists

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correctly answered basic questions about sensitivity and specificity, only 8.6 % were able to correctly compute the positive
predictive value question when it was presented in a probability
format; however, accuracy improved to 63 % when presented
in a frequency format.
Base rates are important for the neuropsychologist to consider
in all conditions but especially important in the forensic evaluation of someone with known or suspected Mild Traumatic Brain
Injury (MTBI). For instance, the base rate of malingering in
plaintiffs with uncomplicated MTBI (negative neuro-imaging)
has been estimated as high as 40 % (Larrabee, 2003).
Moreover, it has been shown in this same population that the
base rate of cognitive symptoms beyond 12 months post-injury
is only approximately 5 % (Carroll et al., 2004; McCrea, 2008).
Thus, if a forensic neuropsychologist is evaluating a plaintiff
who sustained an uncomplicated MTBI 4 years ago but still
presents with numerous cognitive symptoms, it would be unwise
to not consider malingering and a host of other explanatory
factors in the differential diagnosis. That is, the chance of malingering could be as high as 40 % in this hypothetical scenario but
there would be a much higher probability of factors other than
MTBI as the cause of persistent cognitive problems (e.g., preexisting conditions and/or comorbid psychiatric or neurologic
factors would need to be ruled out).
Lees-Haley and Brown (1993) administered a 37-item
checklist to a large sample of personal injury claimants undergoing psychological evaluation for Bemotional distress.^
Subjects, specifically excluded if they had any history of
TBI, seizures, toxic exposure, or other Bneuropsychological
impairment^, were compared to a control group of family
practice patients who presented with routine problems of sore
throat, respiratory problems, headache, flu, and hypertension.
There was not an MTBI control group. The experimental
group (with no neurologic history) endorsed high numbers
of neuropsychological (concentration, memory, word finding,
and organization problems), psychological (anxiety, depression, and loss of interest), and physical (headache, back pain,
and fatigue) symptoms. There are two main conclusions from
these and other studies: First, MTBI symptoms are nonspecific and occur in high frequency in many clinical and
normal-control populations; it is therefore critical for the forensic neuropsychologist to be aware of this base rate data.
Second, relying extensively on MTBI or post-concussion
checklists or self report inventories likely places the neuropsychologist at risk of diagnostic error or faulty conclusions.
Paul Meehl famously pointed out that Bthe chief reason for
our ignorance of the base rates is nothing more subtle than our
failure to compute them^ (in Waller, Younce, Grove, & Faust,
2006. p. 234). Our field now has extensive guides of base rates
with both clinical neuropsychology and general populations.
McCaffrey et al. (2003) systematically documented symptom
base rates for a wide array of medical (HIV/Aids, stroke, and
dementia), psychiatric (learning disability, depression, and

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anxiety), and substance use/exposure (carbon monoxide, recreational drugs including marijuana, alcohol and cocaine, and
pesticides/solvents) conditions. In 2006, McCaffrey, Bauer,
O’Bryant, and Palav published Practitioner’s Guide to
Symptom Base Rates in the General Population. Knowing
the base rates of the condition and symptoms in question will
only increase the forensic practitioner’s diagnostic and predictive accuracy.

Ignoring Normal Variance in Test Scores
Interpretation of neuropsychological test data is an acquired
skill that requires an extensive knowledge base and a clear
understanding of the two issues: the likelihood of an abnormal
score, and the degree of covariance among cognitive domains,
particularly the degree to which intelligence correlates with
other domains. These issues have been thoroughly reviewed
and clearly explained by Greiffenstein (2009) and Binder,
Iverson, and Brooks (2009).
Determining whether a given number of scores reflects
neuropsychological impairment should take into account both
the level at which impairment is defined (e.g., 1, 1.5, or 2
standard deviations below the mean or below an estimated
premorbid level) and the number of tests that were administered. Of course, some pathognomonic signs may reveal impairment despite the overall number of tests not reaching the
threshold typically used for determining impairment. In defining abnormal as more than one standard deviation below the
mean, it can be expected that in a battery of 20 measures
between 10 and 15 % of the scores will be impaired in a
normal-control population (Heaton, Miller, Taylor, & Grant,
2004). In a sample of 327 healthy adults, the use of demographically adjusted scores resulted in even more abnormal
scores (Schretlen, Testa, Winicki, Pearlson, & Gordon,
2008). Therefore, it is a fallacy that all abnormal scores reflect
brain dysfunction and equally incorrect to say that all abnormal scores are acquired.
Although there are instances in which average scores reflect a decline from a previously higher level, it is incorrect to
automatically assume that average scores in an individual of
above average intelligence represent acquired deficits in every
case (Greiffenstein, 2009). Intelligence is not uniformly correlated with other cognitive domains (Diaz-Asper, Schretlen,
& Pearlson, 2004; Dodrill, 1997). Average performance may
result from a variety of factors, including the psychometrics of
a given test (i.e., low ceiling), that are unrelated to cerebral
impairment in a person of above average intelligence.
Therefore, the clinician looking to avoid biased interpretation
of testing data would benefit from considering evidence that
supports and disconfirms two scenarios. In the first scenario,
the lowest scores in the profile are normal variance. In the
second scenario, the lowest scores are reflective of true decline

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from a previously higher baseline. Deliberate consideration of
both scenarios may help to mitigate biased interpretation of
test scores.

Confirmation Bias
Confirmation bias is a psychological phenomenon whereby
an individual preferentially favors information that supports
an original hypothesis and ignores or dismisses data that may
disconfirm the favored hypothesis (Mendel et al., 2011;
Nickerson, 1998). It is the process of seeking information
based on a desired outcome. This bias has been recognized
in philosophy and psychology for decades and was described
as early as 1620 by Francis Bacon (Nickerson, 1998). It is not
unique to medical professionals. In politics and debate, for
example, it is not uncommon for individuals to highlight facts
that are consistent with their positions while simultaneously
dismissing facts that may refute their position. In forensic
science, research has indicated that judging the similarity of
two handwriting samples is directly affected by confirmation
bias, and that confession of a crime can lead to collection of
evidence that fits the confession (Kukucka & Kassin, 2014).
Confirmatory information seeking is often not a conscious
process, but even awareness of confirmation bias does not
make one immune to it (Mendel et al., 2011; Nickerson,
1998). In addition to being aware of the bias itself, neuropsychologists must be continuously aware of their own decision
making processes (Gallagher, 2003). This section details ways
to mitigate confirmation bias at three critical points in the
neuropsychological evaluation: (1) the review of medical records, (2) the selection of questions and use of answers in the
clinical interview, and (3) interpretation of interview and testing data.
Medical records are commonly the first piece of evidence
that a neuropsychologist reviews in process of an evaluation.
Even before embarking on the record review, clinicians are
often able to formulate a hypothesis about the nature of an
injury or illness based on other presenting information. At that
point in the diagnostic process, it is helpful to establish two
competing hypotheses or at least remember the scientific
method of establishing both a hypothesis and its null. If only
one hypothesis is formulated, confirmation bias can arise out
of a tendency to seek information that confirms the one hypothesis (Nickerson, 1998). This may occur in part because of
a preference for reducing the possibility that the original hypothesis was wrong (i.e., Berror reduction^) as one proceeds
through the diagnostic process (Friedrich, 1993).
Confirmation bias occurs more frequently in settings where
hypotheses are considered sequentially as opposed to simultaneously (Jonas, Schultz-Hardt, Frey, & Thelen, 2001). In
addition, research on biased decision making indicates that
after a person commits to a single hypothesis, there is typically

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preference for confirmatory evidence because disconfirmatory
evidence results in too much cognitive dissonance (e.g., Jonas
et al., 2001). Perhaps for this reason, Borum, Otto, and
Golding (1993) recommended a deliberate attempt to search
for disconfirmatory evidence to interrupt the pattern of confirmatory searching (see also, Wedding & Faust, 1989).
Upon embarking on a medical record review, it is important
to keep in mind that information gathered early in the diagnostic process tends to have more weight than information
gathered later (Nickerson, 1998). Given this primacy effect,
clinicians wishing to reduce confirmation bias will seek to
review the most objective sources of information first
(Wedding & Faust, 1989). For example, in a case of traumatic
brain injury, this might be a preferential early review of a
paramedic’s report and emergency department records.
The next step in the diagnostic process is often the clinical
interview. In the effort to avoid confirmation bias and premature commitment to a preliminary diagnosis, the interview is
perhaps the most precarious point of the diagnostic process. If
a bias is already brewing, the clinician can create diagnosis
momentum in the interview by posing only questions that will
confirm a specific hypothesis. This problem can be
compounded by an acquiescence bias on the part of the interviewee who may be inclined to answer affirmatively. To avoid
this situation, it can be helpful to begin a diagnostic interview
as transparently as possible by saying something like BI am
going to ask about a number of symptoms not all of which will
fit your experience.^ Interview questions could be deliberately
balanced between questions that are designed to enhance and
lower confidence in a specific hypothesis. The clinician who
tends to interview in a manner that favors Byes^ responses
may have selected a series of questions in order to confirm a
hypothesis.
The nonbiased use of objective neuropsychological testing
data is easier when a clinician has not prematurely committed
to diagnosis. Committing to an expected level of impairment
or neurobehavioral syndrome before seeing the test scores is a
risk factor for confirmation bias. It also increases the risk of
perceiving Billusory correlations^ (Chapman & Chapman,
1969) between test scores and patient behavior or that injury
A must be associated with symptom B. It is important to
maintain competing hypotheses all the way through the evaluation, including the test data review. If cognitive impairment
is found and a confirmation bias is at work, the etiology of the
cognitive impairment will be automatically biased. In other
words, the clinician who seeks to find cognitive impairment
will, due to a confirmation bias, inevitably try to find cognitive
impairment. Consider the case of MTBI in which a patient
shows evidence of attention impairment on neuropsychological testing 12 months post injury. For the neuropsychologist
who has fallen victim to confirmation bias, he or she may seek
to ascribe the attention impairment to MTBI while ignoring
potentially conflicting or disconfirming information. A

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second contrasting example would be a patient who is
3 months into her recovery from MTBI who also has a preexisting anxiety disorder and evidences attentional deficits on
formal testing. The neuropsychologist who has developed a
bias that attention problems are entirely related to the preexisting anxiety disorder could erroneously exclude any contribution of the MTBI. Specifically, the biased neuropsychologist in this example would unknowingly or deliberately review records, ask interview questions, and interpret test results
in such a manner as to seek information that confirms the
anxiety causation while downplaying or ignoring contributions from the MTBI. In short, there is a need to consider both
factors as MTBI can certainly produce acute attentional problems and concurrent anxiety could exacerbate attentional and
other cognitive problems.

Personal and Political Bias
In the voir dire process of jury selection, attorneys on both
sides of a civil dispute question potential jurors about an array
of attitudes, stereotypes, and life experiences to determine if
bias exists in order to exclude jurors thought unable to be
impartial in evaluating the case at hand. Although forensic
neuropsychologists may undergo voir dire on the stand by
attorneys in attempts to qualify or disqualify them, this selection process does not occur up front for experts who are often
retained on factors as basic as willingness to take a case, availability to meet deadlines, costs, and perhaps recommendations
of a legal colleague. It is then during the expert’s deposition or
cross examination that biases can be probed and exposed if
they exist.
Like the general public, neuropsychologists and their family and friends can be the victim of various adverse life experiences that can shape attitudes and contribute to unconscious
stereotyping or frank bias. For instance, the expert or his/her
family member(s) may have been involved in a motor vehicle
or other accident or be the victim of crime, malpractice, or
negligence through no fault of their own. Careful selfexamination is required here to insure the expert is not biased
by such an event or trying to champion a cause.
Potentially more pervasive and not as obvious as these
major life experiences are political beliefs that vary from slight
affiliation with one political party to a full subscription to an
ideology associated with another party. As of this writing, we
are 15 months away from the next presidential election and
already bombarded in the print, electronic, and television/
radio media with highly polarizing news and advertisements
pertaining to candidates’ views on foreign and domestic policy, the BPatient Protection and Affordable Care Act,^ the role
of government vs. the private sector in health care insurance
and dozens of other hot topic issues. Equally prevalent in the
American two-party system are subtle and obvious political

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views about individual responsibility of citizens, the role and
need (if any) of various social Bsafety nets^ and government
assistance programs, gun rights, safety and violence, tort reform, Brun-away^ jury verdicts, and so on. However, many of
the plaintiffs that the forensic neuropsychologist evaluates are
some of the very individuals that are often the direct and
indirect subject of strong political messages or ideologies associated with one political party or the other (e.g., the victim
or perpetrator of gun violence or motor vehicle accident, the
person with no insurance vs. a defendant with Bdeep
pockets^). In addition to the potential personal and political
biases discussed in this section, Ruff (2009) urged the forensic
examiner to be aware of Bcountertransference issues,^ that is,
examinee characteristics such as age, gender, attractiveness,
ethnicity, and socioeconomic status that could elicit an emotion or reaction in the neuropsychologist that somehow effect
attitudes and expert opinions. There is no guarantee that the
expert’s life experiences, political views or countertransference will or will not shape his/her forensic opinions but vigilance, careful self-reflection, and various Bpractice
guidelines^ as articulated by Ruff (2009) are required to promote impartiality.

Group Attribution Error
Group attribution error refers to the belief that an individual’s
traits are representative of a whole group (Allison & Messick,
1985). The understanding of group attribution error has been
at the core of the social psychology research on racism and
stereotype persistence for many years. Issues of ethnocultural
diversity in neuropsychological assessment are beyond the
scope of this article, but have been reviewed elsewhere (e.g.,
Archives of Clinical Neuropsychology 2007 special edition on
cultural diversity). In our opinion, the applications of group
attribution error can extend to diagnostic categories as well as
culture and ethnicity. The same attribution bias can occur in
the clinician who develops overly rigid expectations about the
ways individuals with certain illnesses should behave and/or
perform on neuropsychological tests. This type of bias may be
present in the clinician who thinks that everyone with
Alzheimer’s disease should present in a certain manner, or
everyone with injury history of MTBI should have a certain
constellation of symptoms, or everyone with fibromyalgia has
a somatoform disorder. The conscientious neuropsychologist
can attempt to mitigate this bias by first examining his/her
personal practice to identify which individual traits or diagnostic categories are most likely to be overgeneralized. It can
then be helpful to carefully analyze the interview and testing
data from those cases to make sure that symptoms are not
being dismissed because they are nonconforming to an expected constellation of symptoms.

Psychol. Inj. and Law (2015) 8:265–280

Diagnosis Momentum
Research has estimated that 75 % of clinician diagnostic failures can be attributed to cognitive error by the clinician, which
can stem from a variety of factors, such as insufficient knowledge, inadequate data obtainment and synthesizing, and/or
faulty data verification (Thammasitboon & Cutrer, 2013). In
addition to the cognitive errors described previously, diagnosis momentum bias is equally relevant and warrants consideration. This bias is defined as the tendency for an opinion or
working diagnosis to become almost certain as it is passed
from person to person, thereby suppressing further evaluation
(Croskerry, 2002). In other words, clinicians may prematurely
and/or inaccurately assign a diagnosis early, and then this
diagnosis gains momentum when subsequent clinicians accept the initial diagnosis, with no consideration of differential
diagnoses. Contributions from the field of cognitive psychology have led to this bias gaining increased attention in the
literature, largely in the medical and emergency department
settings, though with clear relevance for forensic neuropsychological practice.
It is essential that clinicians and forensic neuropsychologists are vigilant to diagnosis momentum bias as the foundations for this bias begins as soon as an individual is given a
diagnosis and is often an unconscious or unintended process
(Vick, Estrada, & Rodriguez, 2013). In an inpatient setting, for
instance, a patient may be labeled as Bdemented^ after
evidencing moderate difficulty on a Mini-mental State
Exam. If care is not taken, this label, applied presumably by
an inpatient treatment team and therefore carrying the weight
of a Bteam^ diagnosis, can follow a patient and have longlasting implications for treatment, even if further assessment
and diagnostic verification have not been attempted. This example illustrates the notion that diagnosis momentum bias is
an example of a systemic error, which in combination with
cognitive biases, can lead to diagnostic errors in all fields of
clinical practice.
The negative consequences of diagnosis momentum bias
extend into the forensic setting. For instance, in a recent legal
case in which one of the authors was involved, a seemingly
well-intended primary care physician (PCP) diagnosed MTBI
and made a number of referrals to other treatment providers
such as speech/cognitive therapy, psychiatry, and psychology.
Throughout the records, all of these clinicians used the same
diagnosis. Approximately 3 years later when this same PCP
was deposed and asked the basis of her diagnosis, she testified
that her patient was involved in a moderate speed automobile
accident and sustained a small laceration to his forehead.
Thus, she concluded, it would be reasonable to assume he
sustained an MTBI based on these and other factors. She
was next confronted with records documenting no loss or
alteration of consciousness, a GCS score of 15, and an affidavit from a witness who stated he had an accurate conversation

Psychol. Inj. and Law (2015) 8:265–280

with the patient at the scene about a sporting event they had
each happened to watch on television the prior night. The PCP
eventually conceded that she did not use any specific MTBI
diagnostic criteria and based the diagnosis exclusively on
what her patient told her. Similarly, when each treatment provider was asked how they arrived at the MTBI diagnosis, they
all testified that they simply used the referring physician’s
diagnosis without independent verification. This example
again highlights the systemic and individual contributions that
can perpetuate this bias.
Diagnosis momentum can also have significant consequences when malingering is the diagnosis. In another recent
case, a forensic neuropsychologist hired by the defense was
evaluating a plaintiff who had been labeled malingering in
prior evaluations. The expert was vaguely aware of the specific indicia of malingering in the past and was also frequently
reminded of these by the retaining attorney. After closely
reviewing the prior reports from both medical and psychological experts, it became clear that malingering was only comprehensively evaluated in the first evaluation, and similar to
the aforementioned example, subsequent evaluators seemed
to concur with the diagnosis with minimal independent verification. Indeed, treatment records at a rehabilitation facility
cited one of the prior evaluations (not the first) in opining that
intervention was Bnot necessary due to the patient’s feigned
symptomatology.^ Although it is possible the plaintiff was
malingering across all evaluations, it is equally possible that
the pejorative nature of this label instantly cast doubt and bias
in subsequent evaluators. Diagnosis momentum in this example can lead to individuals not receiving treatment that is genuinely indicated and can have significant legal ramifications.
It is important to recognize that cognitive biases are inevitable and often occur without intention. Therefore, forensic
neuropsychologists must take proactive steps to mitigate the
risk of this bias. Understanding the nature of cognitive biases
and their prevalence is a recommended fundamental step to
decreasing risk. According to Kahneman (2003), a dualprocess model unifies many theories of decision-making and
can help provide insight into how clinicians think, reason, and
judge efficiently in the diagnostic process. Although it is outside the scope of this article to describe this theory in detail,
applying Kahneman’s (2003) model, clinicians rely on two
modes of decision making, BSystem 1^ and BSystem 2.^
System 1 is comprised largely of non-analytical thinking and
is characterized as intuitive, tacit, and experiential and may be
comprised of pattern recognition. Thus, in a neuropsychological evaluation, once a combination of clinical features is recognized, System 1 mode is enacted and can result in a rapid
diagnosis. However, this method alone is vulnerable to errors
and bias. If the diagnostic pattern is not easily recognized, the
System 2 mode, or analytical thinking, is then activated. The
System 2 mode is described as slow, deliberate, conscious,
and effortful reasoning that is often effective but not as

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efficient, the latter of which can be particularly detrimental
in critical diagnostic conditions where time is of the essence.
Utilizing Kahneman’s (2003) theory as a way to understand
clinical decision making, it follows that methods to protect
against biases will target both System 1 and System 2.
Researchers have proposed several ways in which to mitigate
cognitive biases, including diagnosis momentum, in general
and in relation to these decision-making systems (e.g.,
Croskerry, 2002; Thammasitboon & Cutrer, 2013). Though
many of these interventions are primarily suggestions due to
a lack of proven efficacy in the literature, they warrant consideration as the alternative of inaction in this area is unacceptable. Below is a subset of strategies that can be employed to
address diagnosis momentum bias as well as other cognitive
biases, many of which overlap.
In general, strategies to protect against cognitive bias encompass both a focus on increasing clinician expertise and on
avoiding inherent cognitive errors. The competent forensic
neuropsychologist must keep in mind the importance of
reviewing all available records, including diagnoses, with a
high degree of scrutiny and careful attention to diagnosis momentum. Care should be taken to assess the validity of previously rendered diagnoses, after considering all available information. To do this, the onus is on the neuropsychologist to
have sufficient understanding about any/all relevant diagnoses
which he/she is considering.
Understanding that forensic neuropsychologists typically
review many records prior to an evaluation and therefore are
privy to existing diagnoses, it is prudent for them to engage in
a hypothesis-driven approach to rendering his/her own diagnoses, which must involve carefully considering differential
diagnoses. In other words, asking BWhat else might this be?^
is helpful, and the pause inherent in this questioning can activate the aforementioned System 2 to be used in conjunction
with System 1 (Croskerry, 2003). A useful exercise is to consider and practice how one would explain to a trier-of-fact
why a particular diagnosis would or would not be considered
or ruled out. Obtaining peer consult and feedback can be helpful with this exercise.
Some research has posited that metacognition, or
Bthinking about thinking,^ should be utilized as a method to counteract cognitive biases by increasing awareness of one’s own thought processes and clinical reasoning (Croskerry, 2003; Groopman & Hartzband,
2011). Metacognition may allow a forensic neuropsychologist to reflect upon his/her decision-making skills
and sharpen the ability to identify and prevent cognitive
biases. Croskerry (2003) described five features of
metacognition that can improve clinical reasoning in
the context of System 1: (1) awareness of requirements
of learning process, (2) recognition of limitations of
memory, (3) ability to appreciate perspective, (4) capacity for self-critique, and (5) ability to select strategies.

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Strategies to mitigate diagnosis momentum bias as it may
impact System 2 include ensuring the use of evidence-based
practices and normative decision making, obtaining targeted
training on common errors identified in practice settings and
employing metacognition (Croskerry, 2003). Regarding
System 2, reflection (e.g., upon one’s work or comfort level
with a diagnosis) can also be useful to improve a forensic
neuropsychologist’s self-awareness as well as his/her overall
reasoning process (Croskerry & Nimmo, 2011).

Good Old Days Bias
As this article has highlighted, there are multiple factors that
can impact the validity, outcome, and efficacy of a forensic
neuropsychological evaluation. Most of the previously
discussed factors involve the impact of the cognitive biases
of the evaluator. The Bgood old days^ bias is similar to selfreport bias, in that it is held by the individual being evaluated.
It can impact an individual’s retrospective perception and
reporting of symptoms. This bias is included in this paper
because it is imperative for forensic neuropsychologists to
consider when conducting evaluations, particularly with those
who have, or may have, sustained an MTBI. Research (e.g.,
Dikmen, Machamer, & Temkin, 2001; McCrea et al., 2009)
has indicated that recovery from an MTBI is measured by
examining the resolution of post-concussive symptoms back
to premorbid levels. The Bgood old days^ bias is the tendency
to view oneself as healthier or higher functioning in the past,
or to underestimate symptoms, prior to an injury. Indeed, research has shown that patients with back injuries, general
trauma, and those who have sustained MTBIs, including children, tend to report fewer pre-injury symptoms than the base
rate of symptoms in healthy adult and pediatric samples, and
these patients tend to overestimate the actual degree of change
from pre-injury (Brooks et al., 2013; Davis, 2002; Gunstad &
Suhr, 2001, 2004; Hilsabeck, Gouvier, & Bolter, 1998;
Mittenberg, DiGiulio, Perrin, & Bass, 1992). That is, individuals have a tendency to misperceive or misrepresent their preinjury functioning as better than the average person, which
then negatively impacts their perception of current problems,
recovery from their injury, and ability to return to work (e.g.,
Iverson et al., 2010). This finding is further complicated by
one’s involvement in personal injury civil litigation (e.g., see
above reference to Lees-Haley et al., 1997).
The research into this complex area of science is ongoing,
with interesting and innovative findings driving further research. Recently, noteworthy is the first study to prospectively
evaluate the Bgood-old-days^ bias in different domains of
post-concussion symptoms (PCS) in patients with a history
of MTBI (Yang et al., 2014). Yang et al. found additional
support that the Bgood-old-days^ bias is seen in patients with
a history of MTBI by 1-month post-injury, but that this

Psychol. Inj. and Law (2015) 8:265–280

response bias may diminish by 3-month post-injury. In this
study, PCS was subdivided into physical, cognitive, and emotional domains, and results found that the Bgood-old-days^
bias presented differently in these domains. First, the Bgoodold-days^ bias was prominent in the physical and cognitive
domains but not in the emotional domain. This finding may
suggest that patients with MTBI histories overestimate their
pre-injury physical and cognitive abilities rather than emotional reactions such as depression and anxiety, possibly due to the
fact that medical symptoms are easily viewed as indicators of
medical illness. Yang et al. proposed that patients with MTBI
histories may more readily recognize the pre-injury supernormal status of physical and cognitive abilities versus emotional
symptoms, and thus, it is possible that such emotions may not
be subjectively perceived as a Bsymptom^ during evaluation.
Results also found that the Bgood-old days^ bias involving
cognitive PCS symptoms tended to diminish by 3-month
post-injury. In fact, the Bgood old days^ bias seemed to persist
at a consistent rate only with the physical PCS symptoms.
Yang et al. (2014) hypothesized that this finding could
suggest that the Bgood-old-days^ bias may be a dynamic psychological process that occurs after one sustains a mild injury.
If this is true, the authors suggested that it is important to
continuously monitor patients’ symptom reporting in clinical
settings because of the possibility that the Bgood-old-days^
bias can evolve with time. Awareness of the specific factors
that can contribute to this bias can potentially inform the creation of targeted psychological interventions to address PCS.
To mitigate the risk of obtaining faulty data and/or making
problematic inferences due to the Bgood old days^ bias of
those being evaluated, forensic neuropsychologists must be
aware of the continuously evolving research, and ongoing
controversy, in this area of practice. Several of the aforementioned biases (e.g., self-report bias and underutilization of base
rates) are particularly relevant. Knowledge is crucial from the
state of the science to the accurate assessment of the
premorbid and postmorbid functioning of the individual.
With respect to the latter, it is prudent for forensic neuropsychologists to obtain as much collateral information as available that can help provide insight into the examinee’s pre- and
post-injury states. Reliance on self-report alone is insufficient.
It is also important for forensic neuropsychologists to be
aware of base rates, so that they can have a context in which
to interpret the individual’s current symptoms. For example,
neuropsychologists unfamiliar with base rates may be particularly vulnerable to overpathologizing normal variance. It is
easy to see how this can be further complicated if a forensic
neuropsychologist engages in confirmation bias from the onset of the evaluation. In essence, evaluation of an individual’s
symptoms, and his/her perceptions of symptoms post-injury,
requires thoughtful, pro-active consideration of many factors
to increase the chance of a valid assessment, which is of utmost necessity in civil litigation.

Psychol. Inj. and Law (2015) 8:265–280

Overconfidence
Bias exists in spite of excellent training, professional successes, and desire to be bias free. Bias also is unaffected by
years of experience in practice and is therefore equally likely
to occur in experienced and early career psychologists (Grove,
Zald, Lebow, Snitz, & Nelson, 2000; Sladeczek, Dumont,
Martel, & Karagiannakis, 2006). The overconfidence bias as
it applies to neuropsychology is most related to the accuracy
or precision of one’s diagnostic capabilities (Harvey, 1997).
This bias characterizes the neuropsychologist who is 100 %
certain that they know Bthe truth^, perhaps as a consequence
of the confirmatory bias or diagnosis momentum problems
that are described in other sections of this article. It can lead
to diagnostic errors because of an inability to consider competing hypotheses. Therefore, deliberate consideration of two
competing hypotheses is as essential in reducing overconfidence as it is in reducing confirmation bias. Other ways to
mitigate overconfidence involve requesting periodic peer reviews of forensic reports, and being aware of one’s own limitations in training and experience, including a lack of continuing education in forensic neuropsychology.

Discussion
To be biased is to be human, and neuropsychologists are no
exception. But striving to reduce, manage, or otherwise control the impact of those biases on one’s forensic services is an
essential obligation of neuropsychologists. The above list of
biases is not exhaustive (dozens more exist) nor mutually
exclusive. For instance, the Bgood old days bias^ is a type of
Bself report bias, and Bdiagnosis momentum bias^ is a form of
Bconfirmatory bias.^ Even non-forensic psychologists are
subject to myriad biases that effect their decision making
and judgment. Then, when an adversarial setting with high
stakes and heightened scrutiny is introduced in the forensic
arena, the potential for cognitive biases and diagnostic errors
only increases. In adversarial systems, two equally competent
neuropsychologists can and often do disagree, arguing for
instance that the opposing expert’s written report or methodology suggests confirmation, financial, or referral bias or represents overconfidence. Whereas the cross examination process provides certain checks on revealing bias, jurisdictional
ethics, and licensing boards rarely get involved except in cases
of egregious ethical violations; for instance, the forensic neuropsychologist who provides expert opinions to Bprove^ a
family member’s damages or facilitate their acquittal of an
alleged crime, or the expert who engages in an unethical contingency fee scheme with bonuses and incentives. Ultimately,
however, it is up to the individual professional to monitor
biases and take appropriate steps to reduce and eliminate
them.

277

Although the neuropsychologist has to be attentive to
biases throughout the entire expert witness process, we concur
with Greiffenstein and Kaufmann (2012) that following the
resolution of a case is the ideal time to engage in various
debiasing techniques and what Brodsky (1999) terms an
Bintegrity check.^ When the stress and time requirements of
a legal case are over, the expert can turn his/her attention to
self -examination of bias. We have described specific ways to
mitigate each of the one dozen biases described above: Some
mitigation steps are straightforward and dichotomous (the expert simply does not accept a forensic case on contingency fee
arrangements or provide forensic opinions regarding current
patients). However, a majority of these biases vary in subjectivity, and experts can both knowingly and unconsciously be
subject to committing some or many of them.
Borum et al. (1993) listed various clinical examples with
Bcorrective measures^ to improve clinical judgment and
decision making in forensic evaluations. Martelli et al.
(2003) offered 14 recommendations to promote objectivity
and ethical conduct in medicolegal settings (e.g., BEnsure
against excessive black and white findings. Recognize the
limitations of scientific, medical and neuropsychological
opinion, fewer findings are black or white and attributable to
a single event.^ P. 34). Sweet and Moulthrop (1999) created
two sets of BSelf-examination questions as a means of identifying bias in adversarial assessments.^ Their heuristic approach was discussed from a general standpoint and then regarding the forensic neuropsychology report. Lees-Haley
(1999) provided follow up commentary on these debiasing
procedures, concluding BSweet and Moulthrop’s article
should be viewed as an excellent starting point for further
dialogue. Now we need critical review of the debiasing procedures and process for testing and peer reviewing their
effectiveness^ (p. 47). Unfortunately, the intervening 16 years
has seen a paucity of research on the latter recommendation.
Martinez (2014) appropriately urged the early-career forensic psychologist to develop Bgood habits^ early on regarding
the identification and management of potential bias. However,
some neuropsychologists enter the forensic/adversarial arena
mid to late career. Knowledge is key here and may be obtained, for instance, via continuing education, clinical supervision,
peer consultation, and experience. Developing a small peer
group in which two forensic experts review each other’s reports and deposition/trial transcripts especially for a settled
case that posed unusual challenges can help raise awareness
of bias(es) and develop steps to mitigate. Finally, one could
modify Appendix 1 and utilize it as a simple check-list of
these one dozen biases with notation of those areas (if any)
that proved problematic or the subject of difficult-to-answer
cross examination questions. For instance, has the expert accepted too many referrals from a particular law firm notorious
for withholding records or a difficult-to-work with attorney;
has the expert failed to consider high or low base rates of the

278

subject condition; did a political attitude, group attribution
error, or stereotype interfere with objectivity; or has the expert
relied too heavily on self report and failed to obtain a key
record that he/she was confronted with on the witness stand?
The list is seemingly endless and actions from an honest selfappraisal can guide ways to reduce bias in one’s practice, and
help revise or fine tune methodology to insure the bias does
not happen again or minimally, is controlled as much as
possible.
Compliance with Ethical Standards
Conflict of Interest The authors declare that they have no competing
interests.

Appendix 1
12 Sources of Bias in Forensic Neuropsychology
1. Role bias: Conflating clinical and forensic roles
2. Financial/Payment bias
3. Referral source bias (and retaining attorney pressure)
4. Self report bias (Need for corroborative data)
5. Under-utilization of base rates
6. Ignoring normal variance in test scores
7. Confirmation bias
8. Personal and political bias
9. Group attribution error
10. Diagnosis momentum
11. Good old days bias
12. Overconfidence

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