Allegiance Bias in Forensic Evaluation: Why Expert Objectivity Is Critical and How to Guard Against Bias
One of the most uncomfortable truths in forensic psychology is that bias does not require bad faith. Some of the most experienced, well intentioned experts can drift away from objectivity without realizing it. One of the most well documented examples of this phenomenon is allegiance bias.
Allegiance bias occurs when an expert’s opinions subtly align with the interests, expectations, or narrative of the retaining party rather than remaining grounded exclusively in the data. This bias is rarely overt. More often, it emerges incrementally through framing, selective emphasis, or interpretive choices that favor one side of an adversarial process.
In a courtroom setting, where expert opinions carry significant weight, allegiance bias poses a serious threat to the integrity of forensic work and to the legal system itself.
What Is Allegiance Bias?
Allegiance bias refers to the tendency for forensic experts to unconsciously adopt the perspective or goals of the side that retains them. This may occur despite sincere efforts to remain neutral and scientifically grounded.
It does not require intentional distortion, advocacy, or ethical misconduct. Instead, allegiance bias often manifests in subtle ways, such as:
Framing referral questions in a manner that presupposes a conclusion
Giving disproportionate weight to data that supports the retaining party’s theory
Minimizing or contextualizing contradictory findings
Interpreting ambiguous results in a direction that favors one side
Selecting assessment tools or collateral sources that reinforce a particular narrative
Because forensic psychology operates in an adversarial system, the conditions for allegiance bias are built into the structure of the work.
Why Allegiance Bias Is Especially Dangerous in Forensic Psychology
Unlike treating clinicians, forensic psychologists are not advocating for a patient’s wellbeing. Our role is to provide objective, data driven opinions to assist the court. When allegiance bias enters the equation, even subtly, several risks arise.
First, the fact finder may be misled. Jurors and judges often assume that experts are neutral scientists. Biased interpretation undermines that assumption and can distort legal outcomes.
Second, allegiance bias weakens the credibility of the profession. When experts appear aligned with one side, forensic psychology risks being perceived as outcome driven rather than evidence based.
Third, biased opinions are highly vulnerable on cross examination. Skilled attorneys are adept at exposing selective reasoning, omitted data, or inconsistencies that suggest partiality. Once credibility is damaged, even strong science may be discounted.
Finally, allegiance bias creates ethical risk. Forensic psychologists are bound by professional guidelines that emphasize objectivity, transparency, and accuracy. Unchecked bias can place an expert uncomfortably close to advocacy.
Common Pathways to Allegiance Bias
Allegiance bias rarely appears all at once. It often develops through predictable pathways, including:
Repeated work for the same side, firm, or attorney
Early exposure to case theory before independent data collection
Financial pressure or awareness of future referrals
Over identification with perceived injustice suffered by one party
Emotional reactions to particularly sympathetic or unsympathetic examinees
Importantly, none of these factors require unethical intent. They simply highlight how human cognition operates under pressure.
Guarding Against Allegiance Bias in Forensic Practice
Because allegiance bias is largely unconscious, preventing it requires intentional structure rather than good intentions alone. Several practices are critical.
Data First, Theory Second
Forensic opinions must emerge from the data, not the other way around. Adopting or endorsing a psycholegal theory before assessment, testing, and collateral review are complete undermines the scientific foundation of the evaluation. Some attorneys understandably want the psychological data to support their legal theory. At times, the data do. At other times, they do not. My obligation in either scenario is the same. I must be honest with the retaining attorney and transparent with the court.
The data speak for themselves. My role is not to shape them, reinterpret them, or force them into alignment with a case narrative. My role is to accurately collect, analyze, and explain what the data show and what they do not show. I do not enter an evaluation with an a priori hypothesis about the outcome. Doing so converts the evaluation into an exercise in confirmation rather than inquiry. That is data mining, and in a forensic context, it is unethical. Forensic psychology is not a process of testing whether a preferred conclusion can be justified. It is a process of examining whether the available evidence supports a conclusion at all. When experts begin with a theory and search for data to fit it, allegiance bias becomes inevitable.
Explicit Consideration of Alternative Hypotheses
Actively asking what evidence does not support one’s current conclusion is one of the most effective safeguards against biased reasoning. That question cannot be answered without full access to the available data. This is why I review every piece of evidence and discovery that I can obtain. I do not cherry pick what I examine. I do not limit my review to materials that are convenient or favorable. I require the entire file. End of story.
Partial records invite partial conclusions. When an expert relies on a curated subset of discovery, alternative explanations are artificially narrowed and bias becomes structurally embedded in the evaluation process. Reviewing the full record allows for meaningful hypothesis testing. It permits examination of inconsistencies over time, contextualizes statements and behaviors, and ensures that interpretations are grounded in the totality of the data rather than selective excerpts.
In some cases, comprehensive review complicates the narrative. It may introduce facts that are uncomfortable or inconsistent with the retaining party’s theory. That discomfort is not a problem to be solved. It is the point. Forensic opinions must withstand contradictory evidence, not avoid it. Explicit consideration of alternative hypotheses is not a rhetorical exercise. It is a methodological requirement. Without complete data, the question “What evidence does not support my conclusion?” cannot be answered honestly. Forensic objectivity does not come from restraint in data collection. It comes from intellectual courage in confronting all of the data, even when it makes the opinion harder to defend.
Balanced Reporting
Forensic reports should clearly document both supportive and contradictory findings. Omissions are often more damaging than unfavorable data. In the courtroom, discussing limitations is not optional. It is requisite. Forensic opinions that fail to articulate their boundaries are often more vulnerable than opinions that acknowledge uncertainty.
I have been asked, both in reports and on the witness stand, to opine on whether a specific event actually occurred. That question is fundamentally outside the scope of my role. Forensic psychologists do not determine historical truth. We evaluate psychological functioning, consistency of reporting, symptom patterns, and the relationship between reported experiences and observed data.
When asked whether an event occurred, my answer is straightforward: no one except those who were there will ever know the ground truth.This is why precise language matters. In forensic reporting, we use terms such as “reported event” or “alleged experience” rather than presenting contested facts as established truth. This is not evasive language. It is accurate language. It reflects the reality that forensic psychology operates probabilistically, not omnisciently.
Standardized Methods
Using well validated assessment instruments, transparent scoring practices, and established forensic protocols reduces interpretive drift. In practice, this also means maintaining independence in test selection.
I have been asked by attorneys to use specific psychological tests in an evaluation. That is an absolute nonstarter. Allowing a retaining party to dictate assessment instruments compromises the independence of the evaluation and creates the appearance that the methodology was tailored to achieve a particular outcome. Test selection is a professional judgment that must be guided by the referral question, the examinee’s presentation, and the relevant scientific literature. It is not a strategic decision and it is not subject to negotiation.
I have also been asked, in advance of an evaluation, to disclose exactly which tests I plan to administer. I refuse to do so. Providing that information ahead of time creates a real risk of coaching, intentional or unintentional, and threatens the validity of the data collected.
Clear Role Boundaries
Experts should resist pressure to “help the case” and instead remain anchored to their role as neutral evaluators whose duty is to the court, not the retaining party. I have been asked to provide therapy to an examinee after completing a forensic evaluation, or to “coach” the individual in preparation for testimony or court proceedings. These requests are sometimes framed as being helpful, supportive, or in the client’s best interest. In reality, they fundamentally compromise the forensic role. In each instance, I shut that down. As a forensic psychologist, my role is to serve as an objective evaluator. I am not an advocate. I am not a treating provider. I am not a consultant tasked with shaping presentation or improving how someone appears in court. Once those lines blur, neutrality is lost.
Peer Consultation
Discussing difficult cases with respected forensic colleagues can help identify blind spots and challenge assumptions before opinions are finalized. In my own practice, I have reached out to numerous experts in the field for consultation, often by cold calling or emailing colleagues I have never met when I encounter particularly complex or high stakes issues. These are not conversations designed to obtain validation or support a predetermined conclusion. They are intentional efforts to expose my thinking to scrutiny before opinions are finalized.
A Concrete Example From the Witness Stand
Allegiance bias is often discussed in abstract terms, but it most clearly reveals itself in moments of live testimony.
For example, I have been asked on direct examination by retaining counsel to offer opinions that fell outside the scope of my actual evaluation. This typically occurs when an attorney, intentionally or not, attempts to expand the reach of the expert’s work in real time. The question may sound reasonable on its face, but it asks the expert to speculate, infer, or opine beyond the data collected, the referral question, or the methodology employed.
In those circumstances, my obligation is not to the attorney who retained me. My obligation is to the court and to the integrity of the evaluation itself. The appropriate response is not to accommodate the question, soften it, or attempt to be helpful. The appropriate response is to clearly and respectfully decline.
That often sounds like this:
“That question goes beyond the scope of my evaluation, and I do not have sufficient data to offer an opinion on that issue.”
Or:
“I was not retained to evaluate that specific question, and addressing it would require additional data that I did not collect.”
This is not evasive. It is not uncooperative. It is an essential act of forensic boundary setting. Importantly, this applies even when the question comes from the side that retained me. If an expert allows the scope of their opinion to expand on the stand simply because it benefits the retaining party, allegiance bias has already entered the testimony.
Shutting down one’s own counsel when necessary is one of the clearest indicators of forensic objectivity. It demonstrates to the court that the expert’s opinions are constrained by data, methodology, and ethical limits, not by advocacy or loyalty.
From a practical standpoint, this approach often strengthens credibility rather than undermining it. Judges and jurors tend to trust experts who acknowledge limits, resist overreach, and remain consistent under pressure. Conversely, experts who appear willing to stretch their opinions are far more vulnerable on cross examination.
In forensic psychology, knowing what you cannot say is just as important as knowing what you can. Respecting the boundaries of the evaluation is not a weakness. It is the hallmark of disciplined, ethical expert testimony.
Objectivity Is an Active Process
True forensic objectivity is not passive. It is not achieved by simply intending to be neutral. It requires ongoing self monitoring, methodological discipline, and a willingness to tolerate conclusions that may disappoint the retaining party.
In some cases, the most ethical opinion an expert can offer is one that does not advance the legal strategy of the side who hired them. While this can be uncomfortable, it is precisely what distinguishes forensic psychology from advocacy.
The credibility of our field depends not on always being persuasive, but on consistently being honest, transparent, and scientifically grounded.
In the end, allegiance bias is not a personal failing. It is a human one. Recognizing it, addressing it, and building safeguards against it is what defines ethical and effective forensic practice.
