Identifying the bad guy

April 17, 2012

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

Even babies can tell who's the boss, UW research says

July 27, 2017
The charismatic colleague, the natural leader, the life of the party - all are personal qualities that adults recognize instinctively. These socially dominant types, according to repeated studies, also tend to accomplish ...

Infants know what we like best, study finds

July 27, 2017
Behind the chubby cheeks and bright eyes of babies as young as 8 months lies the smoothly whirring mind of a social statistician, logging our every move and making odds on what a person is most likely to do next, suggests ...

DREAMers at greater risk for mental health distress

July 27, 2017
Immigrants who came to the United States illegally as small children and who meet the requirements of the Development Relief and Education for Alien Minors Act, more commonly known as DREAMers, are at risk for mental health ...

Negativity, be gone—new online tool can retrain your brain

July 27, 2017
Anxiety and depression can have devastating effects on people's lives. In some cases, the mental disorders lead to isolation, poverty and poor physical health, things that often cascade to future generations.

Research aims to shape more precise treatments for depression in women

July 27, 2017
Among women in the United States, depression is at epidemic levels: Approximately 12 million women in the U.S. experience clinical depression each year, and more than 12 percent of women can expect to experience depression ...

Very preterm birth not associated with mood and anxiety disorders, new research finds

July 27, 2017
Do very-preterm or very-low-weight babies develop anxiety and mood disorders later in life? Julia Jaekel, assistant professor of child and family studies at the University of Tennessee, Knoxville, and Dieter Wolke, professor ...

0 comments

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.