Confirmation Bias: An Enemy of Objectivity in Forensic Mental Health Assessments

Confirmation bias is the seeking or interpreting of evidence in ways that are partial to existing beliefs, expectations, or hypotheses. Confirmation bias leads to errors due to access to extraneous, contextual information. These errors have caused a significant number of unjust convictions. This article discusses the origins of confirmation bias and focuses on its relevance in cases involving forensic mental health experts. Forensic clinicians need to assess ambiguous data and emotionally upsetting events. Three additional cognitive biases that fit within confirmation bias in the forensic mental health evaluation context are also discussed: anchor bias (the primacy effect), adversarial bias (the tendency to arrive at an opinion that favors the attorney that retained the forensic expert), and observer bias (the thoughts, feelings, and beliefs that influence expert conclusions). Finally, we discuss approaches to reduce confirmation bias.