“Blinding” Expert Witnesses: An Effective Trial Strategy

Anjelica Cappellino, J.D.

Written by
— Updated on June 23, 2020

“Blinding” Expert Witnesses: An Effective Trial Strategy

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Blinding Expert Witnesses

By any measure, expert witnesses are an integral part of the judicial process. They can break down complex concepts into more palatable formats for the jury while making the facts at hand easier to understand. Although retained by a litigating party, qualified expert witnesses generally bring an air of objectivity and impartiality to a trial, as their opinions are based on evidence. But that does not immunize experts from a certain level of bias, however slight or subconscious.

Like all other human beings, experts are susceptible to being influenced by outside information that may not be relevant to the facts at hand. Even if a qualified expert can minimize such influences when rendering a professional opinion, the jury’s perception of any potential expert bias can be just as, if not more, damaging than a partial expert.

A trial strategy known as “blinding” an expert offers a solution. This strategy refers to the practice of withholding certain pieces of information from the experts that could create unintentional bias. The information withheld is largely dependent upon the bias that the party seeks to avoid. Although not a widespread practice, one 2012 study indicates that “blind experts” are perceived as significantly more credible, persuasive, and doubled the chances of a favorable verdict. In light of the prevalence of experts at trial, blinding experts may become an increasingly utilized strategy.

Why Blind an Expert?

In order to understand the methodology behind purposefully withholding aspects of a case from experts, one needs to recognize the importance of human cognition and the ways our brains process and perceive information. The human brain is not passive, but rather, uses context and expectation to determine how to process information and which pieces of information on which to focus. The ways humans perceive and interpret information, make judgments, and reach conclusions depend on complex cognitive mechanisms in the brain. As a person develops an expertise in a specific area, their cognitive processes also change. An expert is likely to use education, past experience, and training to filter and interpret information.

Although experts possess superior capabilities for understanding the subject matter in which they are qualified, their professional training can also lead to ignoring important pieces of information while fixating on others. Such cognitive processing is found to exist in experts from different fields, from medical professionals to police officers.

Cognitive research has established that judgment and perception are shaped by various factors. While any qualified, responsible expert would not intentionally allow bias to inform their opinion , there are many ways in which an expert could subconsciously develop a biased opinion.

In terms of processing information, there are several informational biases that an expert could develop. A contextual bias occurs when an expert is aware that the case will lead to litigation or trial, oftentimes changing the amount of attention given to the matter. Similarly, an expectation bias or experimenter’s bias refers to situations where an expert’s expectations are higher, which can cause an expert to more quickly conclude the adverse party was negligent. Likewise, hindsight bias can lead an expert to overestimate certain findings once they are aware of their presence. One study conducted on experts in radiology showed that radiologists were more likely to detect strokes when reviewing a CT scan after they already had prior knowledge that an MRI suggested the same.

Other types of biases form throughout the litigation process that occur outside the scope of an expert’s cognitive processes. Selection bias, which is the most prevalent and beyond an expert’s control, occurs when an attorney consults with several (or dozens) of experts and designates the expert with the most favorable opinion. Because such consultations are protected by attorney-client privilege and attorney/work product privilege, only the expert with the favorable opinion is presented to the jury. This practice can also lead to undersampling bias, during which the testimony of an expert may not accurately represent the larger population of the expertise. Lastly, compensation bias and affiliation bias are biases implicit in the adversarial system and refer to the fact that experts are compensated by one party and likewise affiliated with one side of the litigation. Some biases are unavoidable, but blinding an expert to certain information can help minimize partiality, bolster their credibility, and overall, increase the likelihood of a favorable verdict.

How to Effectively “Blind” an Expert

The concept of blinding an expert was developed in 2010 by Christopher T. Robertson, a professor of law at Harvard University. In one form of blinding that keeps the identity of the parties concealed from the expert, Robertson created a set of criteria to follow. First, the parties would contact an intermediary organization. Members of the organization, also blind to the party’s identity, would then select an expert based on the party’s requirements. The expert, without knowing the party’s identity, would be provided a screened set of materials to review and then report their findings. If the findings are not favorable to the party, the relationship can end there without the expert’s report being discoverable by opposing counsel. If the expert’s opinions are favorable, then the “blindfold” can be removed and the expert can testify to trial with the benefit of explaining their “blinded” relationship to the jury for additional credibility. Attorneys would still have to disclose how many blinded experts were consulted, which reduces the risk of selection bias. According to Robertson, “benefits of using initially blind experts in this manner…is that their opinions are more likely to be consistent with the scientific mainstream, more comfortable for the experts themselves, and more likely to be viewed as credible by jurors.”

A 2012 study, The Effects of Blinded Experts on Jurors’ Verdicts, published in the Journal of Empirical Legal Studies, tested Robertson’s hypothesis. 275 mock jurors reviewed video recordings of a medical malpractice case, with each participant randomly assigned a recording of a blind expert testifying for either the plaintiff or defendant. The study found that blinding experts doubled the chances of a favorable verdict and increased the damages awarded to the plaintiff by $100,000.

The need to blind an expert can be present in a variety of different scenarios. For example, forensic science typically requires experts to compare and contrast physical evidence, such as fingerprints, tire marks, or handwriting, found at a crime scene. The expert’s findings are usually couched in the terms of “sufficient similarity,” i.e., the fingerprints found at the crime scene are “sufficiently similar to those obtained from the suspect. Because the examiner of this evidence is the main “instrument of analysis,” the findings are susceptible to bias on both a conscious and subconscious level. Issues concerning bias even arise in the area of DNA evidence, which is arguably considered a more scientific area than other softer sciences.

Overall, the concept of blindness is not new. In science, “double-blind” studies and placebo groups are the norm when conducting research. In academia, blind reviews of student examinations or papers, during which the professor is unaware of the student or author’s identity, are also commonplace. Even in the highly adversarial legal world, the ideal that “justice is blind” is still a pervasive mantra. While not frequently utilized, the process of blinding experts can bring forth an additional layer of credibility and strength to a trial.

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