…scientific research with actual forensic examiners which [showed] that the *same* expert, examining the *same* evidence, can reach different conclusions when they are affected by bias. The problem was also demonstrated in fingerprinting and DNA, very robust forensic domains. […]
Fingerprinting, DNA, CCTV images, firearms, shoe and tire marks, document examination, and so on. When there is no instrument that says ‘match’ or ‘no-match’ and it is in the ‘eye of the beholder’ to make the judgement, then subjectivity comes in, and is open to cognitive bias. Essentially, forensic areas in which there are no objective criteria: where it is the forensic expert who compares visual patterns and determines if they are ‘sufficiently similar’ or ‘sufficiently consistent’. For example, whether two fingerprints were made by the same finger, whether two bullets were fired from the same gun, whether two signatures were made by the same person. Such determinations are governed by a variety of cognitive processes.