New research reveals how little we can trust eyewitnesses

Eyewitness recollections are easily distorted by the views of others. shutterstock

Eyewitnesses statements often play a vital role in securing criminal convictions – police surveys show that eyewitness testimony is the main form of evidence in more than 20% of cases. But that doesn’t mean the evidence is always reliable.

In fact research shows that 75% of false convictions are caused by a inaccurate eyewitness statement. This means up to 100 innocent people could be wrongfully convicted each year of a violent or sexual crime in the UK because of these false eyewitnesses.

Today, the phenomenon of eyewitness misidentification is more familiar to the public because of the Netflix documentary series “Making a Murderer”. Steven Avery, the subject of the documentary, was falsely convicted of rape and spent 18 years behind bars before being exonerated. And eyewitness suggestibility – where witnesses are willing to accept and act on the suggestions of others if false but plausible information is given – was at the heart of the case.

Miscarriages of justice can occur more often than television documentaries would have us believe – across a variety of crimes. William Mills, for example, was falsely identified for robbing a bank in Glasgow. He was sentenced to nine years based on police identification from CCTV images – which showed a man in sunglasses with a scarf over his mouth and chin.

Another notable case was the Jill Dando murder enquiry in 2001. An innocent suspect (Barry George) was convicted of murder after witnesses discussed the case with each other and changed their minds based on the information one witness presented with. One eyewitness went from being “uncertain” to “95% sure” that George was the correct suspect.

Steven Avery’s mugshot. Netflix, CC BY

Of course, it isn’t just that these suspect eyewitness statements can lead to the unsafe conviction of innocent people – it means that the real perpetrators remain at large. And in 48% of cases of wrongful conviction the real perpetrator re-offends – which can be devastating for all involved.

Eyewitness talk

Many factors such as memory decay, poor eyesight and induced stress have already been shown to have an influence in false testimony. But these factors can only explain a small percentage of false eyewitness statements. There is another factor known as “eyewitnesses talk” which comes into play. This is where witnesses discuss what they saw with each other after the event and then change their mind about what they thought they saw based on the evidence of another witness.

Witnesses talking after an event is a pretty common phenomenon, a survey found that 86% of real eyewitnesses claim to have discussed the event with other witnesses prior to giving evidence. And this is where the process of “co-witness conformity” occurs – in other words eyewitnesses are influenced into including things they didn’t actually see in their statements.

But while previous research has proved that such processes can occur, very little is known about why some people are more likely to do this, or what influences people to change their statements in the first place.

Finding out the truth

A team of investigative psychologists from the University of Huddersfield has been undertaking a series of experiments on more than 600 participants to simulate the event of witnessing a crime. In our research, groups of participants were shown actual footage of a bar fight taking place.

In some of the participant groups we planted actors who were instructed to suggest the wrong man had started the violence. Participants were then interviewed and asked to identify the person who had started the fight.

The results found that eyewitnesses were susceptible to accepting false information from other witnesses and would then include the “evidence” in their own statements. One cause of this suggestibility was due to participants doubting their own judgement after being exposed to the contradicting information. But we also found that eyewitnesses had genuinely convinced themselves they too had witnessed this false information.

Rethinking the evidence

In the group without any actors, 32% of participants gave incorrect statements – which was put down to factors such as poor eyesight and memory. But when actors were planted in the group, 52% of the “real” participants gave an incorrect statement. And worryingly, when more than two actors were planted in a group, almost 80% of the participants ended up giving the same incorrect statement and identifying an innocent man as the culprit.

Our experiment also found that people with submissive and neurotic personalities were far more likely to relay false information in such a setting – as it may be that these types of people are more susceptible to this type of inadvertent manipulation.

What all this shows is that witness testimony is one of the least reliable forms of evidence. And this is why we are now using our research to help identify ways the police can prevent eyewitnesses from relaying false information.

Not such an expert after all. Shutterstock

Going back to the famous example of Making a Murderer, the chances are that in the case of Avery’s first conviction, the witness did not intentionally fabricate her identification. Instead, constant exposure to misinformation by the police after the event contaminated her original memory of what happened. And subsequently, her failure to correctly differentiate between what she witnessed and what she later found out will have led her to believe Avery was indeed the assailant.

Avery was originally sentenced to 32 years in prison for a wrongful sexual assault conviction, of which he served 18. Who knows how many people are serving just as long behind bars because of someone’s well-meaning but false identification.