Perceiving the Crime Some kinds of persons and events are more difficult to perceive than others. Com- mon sense tells us that a quick glimpse, bad lighting, long distance, physical dis- guise, and distraction can all limit a witness’s perceptions. In one study, for example, Rod Lindsay and others (2008) had approximately 1,300 participants observe a tar- get person, outdoors, at one of various distances ranging from 5 meters (16 feet) to 50 meters (164 feet). They found, first, that the witnesses were not accurate at estimating distance and, second, that the further witnesses were from the target, the less accurate they were at identifying the target in a lineup shortly afterward.
Research has uncovered other aspects of the witnessing situation that can impair accuracy. Consider the effects of a witness’s emotional state. Often people are asked to recall a bloody shooting, a car wreck, or an assault— emotional events that trigger high lev- els of stress. In a study that illustrates the debilitating effects of stress, Charles Morgan and others (2004) randomly assigned trainees in a military survival school to undergo a realistic high-stress or low-stress mock interrogation. Twenty-four hours later, he found that those in the high-stress condition had difficulty identifying their interrogators in a lineup. In another study, Tim Valen- tine and Jan Mesout (2009) fitted adult visitors to the London Dungeon—a house of horrors—with a wireless heart monitor and asked them afterward to describe and identify a scary person they had encountered inside. The more anx- ious visitors were in the Dungeon, the less accurate they were later at describing and identifying the scary person in a lineup.