I have an “Oh No!” file. The “Oh No!” file is filled with psychological reports from my peers that are filled with procedural and even ethical errors. This blog focuses on common forms of bias that sneak into an evaluation. We’re all human, and I’ve made my fair share of mistakes. But the goal for the Court should be excellence.

“Just the facts, ma’am” was the famous line attributed to Sergeant Joe Friday in the Dragnet parodies created by Stan Freberg. Unfortunately, instead of “just the facts”, bias infects many psychological evaluations. Bias, intended or unintended, obscures or twists “the facts” such that justice is diluted or denied in court.

Bias is rooted in the concept of cognitive distortion. A cognitive distortion is an irrational or exaggerated pattern of thinking that results in a person perceiving reality inaccurately. There are many different types of cognitive bias, and consequently, bias. Because our focus is forensic psychology, bias may involve the inability or unwillingness of the forensic psychologist to consider alternative points of view.

Impartial neutrality, not bias, should be the hallmark of a forensic psychologist when undertaking a psychological evaluation for the court. The American Psychological Association Specialty Guidelines for Forensic Psychology makes this clear in the Responsibilities Section 1.02 Impartiality and Fairness 1:

When offering expert opinion to be relied upon by a decision maker, providing forensic therapeutic services, or teaching or conducting research, forensic practitioners strive for accuracy, impartiality, fairness, and independence (EPPCC Standard 2.01).  Forensic practitioners recognize the adversarial nature of the legal system and strive to treat all participants and weigh all data, opinions, and rival hypotheses impartially.

When conducting forensic examinations, forensic practitioners strive to be unbiased and impartial, and avoid partisan presentation of unrepresentative, incomplete, or inaccurate evidence that might mislead finders of fact.  This guideline does not preclude forceful presentation of the data and reasoning upon which a conclusion or professional product is based.

This inviolable forensic principle is echoed in the American Psychological Association’s Ethical Principles of Psychologists and Code of Conduct Standard 2.012 as noted above.

For the ethical and conscientious psychologist, bias is unintended and undesired. Best standards of practice are diligently followed in an effort to avoid bias. Nevertheless, bias is still found in most reports, including the reports of excellent psychologists. The professional who claims to be unbiased is foolish. Following is a list of a few types of bias.

Primacy & Recency: A person tends to emphasize information that is encountered at the beginning of an examination (primacy), or alternatively, most recently in the examination (recency). For example, suppose that a father is interviewed several times at the beginning of a custody evaluation, and then a month later the mother is interviewed. The evaluator may have a primacy bias that favors the information gathered early in the evaluation, and may view the mother’s account as untruthful or of lesser value. As an attorney reviewing a report with multiple key litigants, pay attention to the order in which people were interviewed, and the amount of time spent with each person. A good evaluator will alternate between key litigants, and allot similar amounts of interview time in an effort to minimize recency and primacy bias. It also may be helpful to learn when the evaluator began to write the report. A report written piecemeal after each interview risks recency and primacy bias.

Data Selection:  A good evaluation is based on multiple sources of data, with an emphasis on third party information rather than information from friends and family. For example, a criminal exam of mental state (MSO) at the time of offense should have interview information from the defendant, witnesses or alleged victims, records from a myriad of sources, psychological testing, depositions and so forth. An MSO evaluation that has an interview of the defendant and a few legal and police records is fatally flawed due to limited data selection. By the same token, a custody evaluator that omits interviews with the children is in no position to offer an opinion on “the best interests of the child” because the children had no voice in the evaluation. An attorney reviewing a report should inquire about the impact of missing information on the evaluator’s report. Even if there is a good reason for omitted data, a good evaluator will mention the potential impact, good and bad, of the missing data in the report.

I’m The Expert:  One of the most blatant forms of bias is, “I’m telling you how it is because I’m a highly trained, respected expert in the field” without any convincing scientific support or data. This argument on the part of the expert is lazy, arrogant or desperate. This form of bias is also known as “ipse dixit”, meaning “it’s true because I said so.” Sadly, the opinion of an expert psychologist unsupported by research and reliable procedures is about as valuable as a coin toss. An expert is obligated to offer reliable information that is well accepted within the profession and beyond the usual knowledge of the court, not their “soap box” opinion. I vividly recall being involved in a highly contested competency to stand trial evaluation that resulted in expert testimony from four forensic psychologists. The first three (including me), had written well researched and reasoned reports opining that the defendant was not competent to stand trial. The fourth psychologist resorted to loudly and repeatedly proclaiming “he’s lying!!!” without any significant supporting evidence. Maybe the defendant was lying. But arguing like a politician is hardly the hallmark of an impartial forensic psychologist serving as an expert witness.

The notion that a psychological evaluation is totally unbiased is silly. Every report has some form of bias. The core issue for the attorneys and trier of fact is whether a conscientious effort has been made, using best standards of practice, to minimize bias. A good forensic psychologist should be able to identify his or her susceptibility to different forms of bias, and provide a description of the efforts taken to minimize bias.

Future blogs will discuss other forms of bias in my effort to help attorneys learn how to discern good psychological work product from the bad.

  • American Psychological Association (2013) Specialty Guidelines for Forensic Psychology. American Psychologist, 68 (1) 7-19.
  • American Psychological Association’s (2010) Ethical Principles of Psychologists and Code of Conduct including 2010 Amendments.