The vision in "blind" justice: expert perception, judgment, and visual cognition in forensic pattern recognition.

Many forensic disciplines require experts to judge whether two complex patterns are sufficiently similar to conclude that both originate from the same source. Studies in this area have revealed that there are a number of factors that affect perception and judgment and that decisions are subjective and susceptible to extraneous influences (such as emotional context, expectation, and motivation). Some studies have shown that the same expert examiner, examining the same prints but within different contexts, may reach different and contradictory decisions. However, such effects are not always present; some examiners seem more susceptible to such influences than do others--especially when the pattern matching is "hard to call" and when the forensic experts are not aware that they are being observed in an experimental study. Studying forensic examiners can contribute to our understanding of expertise and decision making, as well as have implications for forensic science and other areas of expertise.