NACDL

Though hardly a new subject, discussion about the influence of cognitive bias on the evaluation of forensic science evidence has intensified recently. Academics have warned of the dangers of unconscious biases among forensic examiners for years, but their arguments have gained traction in light of some innovative research studies and the momentum for forensic reform brought about by the National Academy of Sciences’ 2009 report, “Strengthening Forensic Science in the United States: A Path Forward.”¹ 

Generally speaking, cognitive bias refers to distortions in perception and judgment that occur in certain situations.² For example, the perception of a stimulus may be influenced by its surroundings. In Figure 1, although the orange circles are the same size, one appears larger than the other due to the size of the circles around them. Similarly, the shades of gray in Figure 2 are identical, but appear darker or lighter depending on the background. In order to deal with compl