Identifying the bad guy

April 17, 2012, Flinders University

Flinders University psychologist Professor Neil Brewer is proposing a radical alternative to the traditional police line-up, arguing current eyewitness identification tests often fail to pick the culprit, or worse, wrongfully accuse innocent suspects.

Professor Brewer, Dean of the School of Psychology, has devised a new type of line-up where witnesses are simply asked how confident they are that each line-up member is the culprit, and must respond within a few seconds, rather than trying to point out the and having more time to mull it over.

His technique, called “deadline confidence judgements”, has been trialled on more than 900 community members, with the results soon to be published in Psychological Science, one of the world’s most influential psychology journals.

In several experiments conducted over the past three years, Professor Brewer said volunteers watched short films depicting crimes or a mundane event in which one person was prominent.

Half of the participants – some a week later and others within five minutes of the films – were then shown a series of individual pictures from a line-up of 12 people and asked to make a confidence decision about each face within three seconds of it appearing on the computer screen.

They were asked to choose one of 11 options, ranging from “absolutely confident that this is the culprit” to “absolutely certain this is not the culprit”, while the other half of the participants were shown the same faces but given as long as they liked to answer whether each face was or was not the culprit. Sometimes the photos included the culprit and sometimes they did not.

Professor Brewer said a classification “algorithm” produced overall classification accuracy that was 20 to 30 per cent higher than results produced with the conventional line-up.

Moreover, he said the researchers were able to identify particular patterns of confidence judgments across lineup members which showed either a very high or very low likelihood that any individual witness was accurate.

Limiting the time witnesses had to look at suspects yielded better results, Professor Brewer said, because past research showed accurate eyewitness identifications were made significantly faster than inaccurate ones, and that a number of outside factors were removed with a short deadline.

“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 line-up, with plenty of time to reflect on their decision,” Professor Brewer said.

“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 such as the quality of viewing conditions, attention constraints and social cues that bias the witness towards a positive identification – for example “I saw him for a long time so I should know the answer”.”

Professor Brewer said traditional identification tests often failed because the witness felt “under pressure” to identify a guilty party, however his study showed they were more likely to make accurate identifications if they did not have to be so precise.

“A victim of an assault, for example, has plenty of time to reflect on their decision so they’re more likely to think “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”, but in a deadline confidence judgement you’re not asking for a yes or no answer.”

Professor Brewer said the rising number of DNA exonerations and the frequent failure of witnesses to identify the mounted a compelling case for a new system of line-ups.

“The fallibility of eyewitness evidence has been consistently highlighted in lab and field studies, and the potency of mistaken identifications has also been dramatically highlighted by the number of DNA exoneration cases,” he said.

Explore further: Researcher uses card trick to reveal unconscious knowledge

Related Stories

Researcher uses card trick to reveal unconscious knowledge

November 17, 2011
(Medical Xpress) -- Spanish neuroscientist Luis Martínez of the Institute of Neurosciences in Alicante, has shown that an exception exists regarding “change blindness” and it can be demonstrated by using ...

Recommended for you

People with prosthetic arms less affected by common illusion

January 22, 2018
People with prosthetic arms or hands do not experience the "size-weight illusion" as strongly as other people, new research shows.

Intensive behavior therapy no better than conventional support in treating teenagers with antisocial behavior

January 19, 2018
Research led by UCL has found that intensive and costly multisystemic therapy is no better than conventional therapy in treating teenagers with moderate to severe antisocial behaviour.

Babies' babbling betters brains, language

January 18, 2018
Babies are adept at getting what they need - including an education. New research shows that babies organize mothers' verbal responses, which promotes more effective language instruction, and infant babbling is the key.

College branding makes beer more salient to underage students

January 18, 2018
In recent years, major beer companies have tried to capitalize on the salience of students' university affiliations, unveiling marketing campaigns and products—such as "fan cans," store displays, and billboard ads—that ...

Inherited IQ can increase in early childhood

January 18, 2018
When it comes to intelligence, environment and education matter – more than we think.

Modulating molecules: Study shows oxytocin helps the brain to modulate social signals

January 17, 2018
Between sights, sounds, smells and other senses, the brain is flooded with stimuli on a moment-to-moment basis. How can it sort through the flood of information to decide what is important and what can be relegated to the ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.