November 01, 2015

Cognitive Bias and Its Impact on Expert Witnesses and the Court

By Itiel E. Dror, Justice Bridget M. McCormack, and Jules Epstein

Disclaimer: This article reflects the position of the authors and does not reflect or represent any government office, agency or other institution.

Expert evidence provides a much needed contribution to the courts in administering justice. Understanding the way humans think and how the brain processes information offers insights to circumstances in which even expert evidence may be influenced by contextual information and cognitive bias. Cognitive science can identify such potential weaknesses and suggest practical ways to mitigate them.

Courts rely on expert witnesses and mostly assume that they provide impartial and objective evidence. Yet cognitive science shows that even the most dedicated and committed experts are influenced, without even realizing it, by factors unrelated to the data relevant to form their expert conclusion. For example, it has been demonstrated that experts’ conclusions on whether crime scene evidence was left by a specific person were influenced by whether they were told that the suspect confessed or, alternatively, that the suspect could not have committed the crime because of a rock-solid alibi. Because juries and judges often depend on reports and testimony from experts it is important to understand the limits and potential vulnerabilities of those witnesses. At the same time it is critical to find ways to increase and improve the contribution experts make to the fact-finding process.

This article will review and summarize the relevant science, discuss how other nations have responded to this problem, and address how the issue of cognitive bias might be confronted in criminal proceedings in this country.

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