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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 muchneeded contribution to the courts in administering justice. Understanding the way humans think and how the brain processes information offers insights into 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 conclusions. 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 probably did not commit the crime because he has an alibi. Since 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.
Human Cognition and Expertise
Our brains have limited capacity, but they are nevertheless very effective and efficient. This is because they are not passive but instead actively use context and expectation to determine which information to process and how to process it. The human mind is not a camera but rather selects "parts of a picture" on which to focus. Complex cognitive mechanisms are involved in the way in which humans perceive and interpret information, make judgments, and reach decisions.
These cognitive mechanisms stand at the heart of intelligence and expertise. Paradoxically, as people become experts, their brains change and develop very useful capacities, but these very mechanisms can also increase the susceptibility to bias. For example, the cognitive underpinning of expertise entails...