Policing: Placing people who do NOT look the same in line-ups can improve accuracy by 10 per cent

Is THIS the key to improving eyewitness identification? Placing people who do NOT look the same in police line-ups can improve accuracy by 10%, surprising study reveals

  • US and UK researchers recruited 19,732 volunteers to play the role of eyewitness
  • Each participant was shown a video of a faked crime, followed by a photo line-up
  • The team tried line-ups of people that were more and less similar to the suspect
  • Less similar line-ups were found to improve the accurate detection of the perp.
  • Yet they did not increase false positives in line-ups with just innocent suspects 

The accuracy of identity parades could be improved by 10 per cent by including people who do not all look the same as the suspect in police line-ups, a study found. 

Researchers from the US and the UK recruited more than 19,000 participants to play the role of eyewitnesses in a line-up after witnessing the recording of a faked crime.

They found that people were more likely to identify the perpetrator correctly if they were shown photos of faces that were dissimilar, rather than similar, to the suspect.

However, they were not at the same more likely to incorrectly ‘finger’ an innocent suspect in a line-up where the real perpetrator was not present.

The approach differs from that conventionally taken, in which the ‘fillers’ making up the rest of line-up is chosen to broadly resemble the suspect or witness descriptions.

The accuracy of identity parades could be improved by 10 per cent by including people who do not all look the same in police line-ups, a study has revealed

‘In practice, police tend to err on the side of picking facially similar fillers for their line-ups,’ said paper author and psychologist John Wixted of the University of California San Diego.

‘What our study shows is that it is, contrary to intuition, actually better to pick fillers who are facially dissimilar.’

‘Doing it this way continues to protect the innocent to the same degree while helping witnesses to correctly identify the guilty more frequently.’

In their study, Dr Wixted and colleagues played a mock-crime video showing a white male stealing an office laptop, to 19,732 volunteers.

After viewing the footage, each participant was shown six photographs, one of whom was a ‘suspect’ — and either the perpetrator or an innocent person.

The other five images were of police line-up fillers, each of whom were similar, to varying degrees (as previously rated by a different set of volunteers), to the suspect.

The team found that picking ‘filler’ images of people who were facially dissimilar to the suspect improved the ability of eyewitnesses to pick out the perpetrator when he was in the line-up.

At the same time, however, this did not increase the likelihood of the witness wrongly identifying an innocent suspect when the perpetrator was not part of the identity parade — what the team dub ‘false alarms’.

‘Eyewitness misidentifications have contributed to many wrongful convictions, which are later overturned by DNA evidence,’ said paper author and psychologist Melissa Colloff of the University of Birmingham.

‘Failing to identify a perpetrator when he is in the line-up can also result in guilty perpetrators being free to commit additional crimes.’

‘Although many useful reforms have been introduced to protect the innocent, sometimes these will also protect the guilty.’

The findings, she added, prove one police line-ups can be made more effective for everyone, ‘increasing the likelihood that a guilty perpetrator will be identified, without increasing the likelihood that an innocent suspect will be imperilled.’

The full findings of the study were published in the journal Proceedings of the National Academy of Sciences


The big pause: Lying is quite a complex process for the body and brain to deal with. First your brain produces the truth which it then has to suppress before inventing the lie and the performance of that lie. 

This often leads to a longer pause than normal before answering, plus a verbal stalling technique like ‘Why do you ask that?’ rather than a direct and open response.

The eye dart: Humans have more eye expressions than any other animal and our eyes can give away if we’re trying to hide something. 

When we look up to our left to think we’re often accessing recalled memory, but when our eyes roll up to our right we can be thinking more creatively. Also, the guilt of a lie often makes people use an eye contact cut-off gesture, such as looking down or away.

The lost breath: Bending the truth causes an instant stress response in most people, meaning the fight or flight mechanisms are activated. 

The mouth dries, the body sweats more, the pulse rate quickens and the rhythm of the breathing changes to shorter, shallower breaths that can often be both seen and heard.

Overcompensating: A liar will often over-perform, both speaking and gesticulating too much in a bid to be more convincing. These over the top body language rituals can involve too much eye contact (often without blinking!) and over-emphatic gesticulation.

The more someone gesticulates, the more likely it is they might be fibbing (stock image)

The more someone gesticulates, the more likely it is they might be fibbing (stock image)

The poker face: Although some people prefer to employ the poker face, many assume less is more and almost shut down in terms of movement and eye contact when they’re being economical with the truth.

The face hide: When someone tells a lie they often suffer a strong desire to hide their face from their audience. This can lead to a partial cut-off gesture like the well-know nose touch or mouth-cover.

Self-comfort touches: The stress and discomfort of lying often produces gestures that are aimed at comforting the liar, such as rocking, hair-stroking or twiddling or playing with wedding rings. We all tend to use self-comfort gestures but this will increase dramatically when someone is fibbing.

Micro-gestures: These are very small gestures or facial expressions that can flash across the face so quickly they are difficult to see. Experts will often use filmed footage that is then slowed down to pick up on the true body language response emerging in the middle of the performed lie. 

The best time to spot these in real life is to look for the facial expression that occurs after the liar has finished speaking. The mouth might skew or the eyes roll in an instant give-away.

Heckling hands: The hardest body parts to act with are the hands or feet and liars often struggle to keep them on-message while they lie. 

When the gestures and the words are at odds it’s called incongruent gesticulation and it’s often the hands or feet that are telling the truth.


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