While eyewitness identification evidence is frequently used in the courtroom, many studies show that an alarming number of witnesses fail to pick up the culprit, and worse, witnesses sometimes wrongfully accuse innocent suspects.
While witness accounts will never be 100 percent accurate, scientists have found a way to boost the accuracy of identification tests by focusing on eyewitnesses' confidence judgments.
In a new study, expected to be published in the forthcoming in Psychological Science, lead researcher Neil Brewer of Flinders University and his team found that the new type of lineup based on "deadline confidence judgments" produced results that were 20 to 30 percent more accurate than results produced in a conventional lineup.
Researchers explained that in the new lineup, witnesses would be presented with lineup photos one at a time and would then rate how confident they are that the person in each photo is the culprit. However, researchers stressed that witnesses would not be allotted time to think over their assessments and must respond within a few seconds.
Brewer and his team tested the new witness identification technique by showing participants short films depicting crimes or a mundane event in which there was one prominent character.
Afterwards, either five minutes later or a full week later, researchers showed half of the participants a series of separate pictures from a lineup of 12 people and asked to make a confidence decision on a scale of 1 to 11, ranging from "absolutely confident that this is the culprit" to "absolutely certain this is not the culprit" about each face within three seconds of it appearing on a computer screen.
Participants in the control group were shown the same faces but given as long as they liked to answer whether each face was or was not the culprit via 'yes' or 'no' answers.
Researchers noted that sometimes photos included the culprit and sometimes they did not.
Results from the study showed that participants in the confidence ratings group were 20 to 30 percent more accurate than the control group.
Additionally, researchers added that they were able to identify particular patterns of confidence judgments indicating how reliable witnesses were, showing that accurate eyewitness identifications are made significantly faster than inaccurate ones.
Researchers explain that the new line-up may produce more accurate results because a large number of external factors are eliminated with a short deadline, like conditions under which people view lineup photos, constraints on attention, and social cues that bias the witness towards a positive identification.
"A weakness of the traditional test lies in the fact that it requires a witness to make a single 'yes' or 'no' decision about a lineup, with plenty of time to reflect on their decision," Brewer said in a statement. "But the time lapse from the initial viewing to the response often mitigates against witnesses making accurate decisions, as does an array of external factors."
Researchers say that traditional identification tests often fail because the witness feels the burden to identify a guilty party. They say that witnesses are more likely to make accurate identifications in the new lineup because they do not have to be so precise.
Brewer explains that with plenty of time to reflect on their decisions, witnesses are more likely to feel the stress related to the potential consequences of not picking out the culprit, thinking 'If I don't pick this person, a dangerous man may go free' or 'If I do pick the suspect, I'd better be right.'
However, with a deadline confidence judgment, this pressure is eliminated because the witness doesn't have to provide a 'yes' or 'no' answer.