Expert Witnesses BlindingIntroduction:

Expert witnesses are so prevalent in litigation that it is commonplace for attorneys to be familiar with them and to have myriad working relationships with them.

From cases concerning issues of patent law to radiology, a number of legal commentators and jurists have suggested that “blinding” experts may be a way to reduce potential bias in their testimony.

This article analyzes the concept of blinding experts and what the implications for the legal community may be.


There are several ways in which attorneys who retain expert witnesses can blind them, including blinding the experts to contextual factors and blinding them to legal standards.

The concept of blinding was developed and articulated in 2010 by Christopher T. Robertson, a professor of law at Harvard University. See, e.g., Dr. Ken Broda-Bahm, “Consider a Blind Expert Witness,” Persuasive Litigator, Nov. 15, 2012, at (last visited Sep. 20, 2017.

Blinding typically involves not providing a retained expert with information regarding certain aspects of a case.

For example, in one form of blinding, an expert does not initially know the identity of the party involved in the litigation.

Under Robertson’s formula, the following criteria should be met for an expert to be properly blinded:

  • If they wish, parties would contact an intermediary organization. Members of that organization, also blind to the identity of the party, would then select from a pool of prequalified experts based on criteria provided by the party.
  • The hired expert would learn about the case via a screened set of materials and, without knowing the identity of the hiring party, would draft the preliminary expert report laying out the main conclusions.
  • If the conclusions are not helpful to the hiring party, that party would simply pay and walk away. The fact that a blind expert was consulted would not be subject to discovery.
  • If the conclusions are helpful, on the other hand, the blindfold would be lifted and the expert would be able to testify not only about their conclusions, but also about the process and the fact that their initial report was produced under blind conditions.
  • In the event that a party chooses to use a blind witness, that party would need to disclose all prior blind witness arrangements (to prevent the party from trying multiple times until they get a ‘hit’ with a blind expert).
  • Nothing would prevent either party from hiring a paid expert instead of or in addition to the blind expert.” Id.

The idea behind Robertson’s formula is that blind experts will be less likely to give potentially biased testimony and will also be considered more credible.

Specifically, “benefits of using initially blind experts in this manner, according to Robertson, 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.” Id.

Moreover, researchers who have tested the theories advanced by Robertson have found that experts who are blinded in the manner discussed above are seen as more credible and achieve substantial successes in the courtroom. See id.


There are many techniques available to litigators to help establish their experts’ credibility and objectivity.

In a recent Canadian patent law case, a federal court acknowledged that Robertson’s model may be one factor that can help to accomplish these objectives. See PCK Reporter, “Federal Court finds Expert Blinding to be One Factor in Assessing Weight Given to Expert Evidence,” Lexology, Sep. 19, 2017, at (last visited Sep. 20, 2017).

Another publication in the US regarding radiology cases made similar conclusions. See Daniel J. Durand, et. al, “Expert Witness Blinding Strategies to Mitigate Bias in Radiology Malpractice Cases: A Comprehensive Review of the Literature,” Journal of the American College of Radiology, Jul. 16, 2014.

In any event, blinding expert witnesses via the Robertson method may provide attorneys with additional resources to help their experts shine in the courtroom and to secure the verdicts they are hoping for.