Harmful evidence – wrongful conviction or suspicion on the basis of flawed eyewitness testimony

You’ve probably heard people say “I never forget a face” and “I’d definitely recognise him again if I saw him”. But is this really the case, and how should an eyewitness’s memory of the face of the perpetrator be used within the criminal justice system?

Although warnings are given to juries regarding the potential unreliability of eyewitness testimony, not least because research has indicated that our memory of “who done it” may not always be as good as we think, such evidence still features very prominently in most criminal investigations and trials. In addition, eyewitness testimony is often the only direct evidence available that a particular person committed a particular act. Although forensic evidence, such as fingerprints and DNA analysis, can be very useful in establishing that a person was at a particular place or handled a particular object, it only provides indirect evidence that they committed the crime. For example, you may well be familiar with the potential problem of using indirect evidence to determine what happened from popular crime dramas, which often feature the situation where an innocent person helps a victim, and in so doing puts their fingerprints on the murder weapon and gets the victim’s blood on their clothes.

In 1992, the Innocence Project was established in the USA. This project takes up the cases of people who claim to have been wrongly convicted of a crime where DNA testing could potentially exonerate them. To date, 318 convictions have been overturned and innocent victims of injustice released, included eighteen men who were on death row. The average period of wrongful imprisonment is nearly fourteen years. The Innocence Project website reports that “Eyewitness misidentification is the single greatest cause of wrongful convictions nationwide, playing a role in 72% of convictions overturned through DNA testing”. The problem of erroneous eyewitness identification is not confined to the USA: in 2009 William Mills received a nine year jail sentence after being convicted of robbing a Glasgow bank. A critical part of the evidence was the identification by two police officers of Mills from CCTV footage. Two customers who had been in the bank at the time also picked Mills out from an identity parade. Mills was cleared of all charges and released six months into his sentence after DNA found at the scene was subsequently matched to a different person.

In 2005, the first Innocence Project was set up in the UK at The University of Bristol Law School. Although the achievements of Innocence Projects and other similar organisations are important, and indeed life changing for many, they can only correct miscarriages of justice in cases where alternative evidence is present. DNA left at the scene of the crime is often used; however, frequently the perpetrator avoids leaving samples, or by the time a case is reopened any traces have deteriorated. It’s therefore important that we explore why the misidentifications occur in the first place and how they might be avoided.

A first stage is to tackle the myth that we are good at identifying faces.  We are – but only in some circumstances, notably where the face is very familiar to us. However, evidence from psychology experiments shows that we are poor at recognising a face we’ve only encountered briefly. A typical experiment involves showing participants a video of a staged crime involving an unfamiliar person acting the role of perpetrator. Later the participants are presented with a set of photographs or video clips which may or may not include the perpetrator. The rate of correct identifications made varies depending on the exact procedure – but less than 50% accuracy is not unusual. Perhaps more surprisingly, Megreya and Burton (2008) demonstrated that even when people are shown a photograph of a face (the target) then immediately presented with a set of photographs and asked to identify the target, they are only accurate about 70% of the time.

The low accuracy rates reflect the fact that remembering is not like taking a photograph: we don’t record an exact copy of what we see, and what we recognise is influenced by many other factors than simply what we observed. A rather dramatic example of how recognition can be affected by extraneous factors is the case of psychologist Donald Thompson. Thompson took part in a live discussion on Australian TV and on his way home was arrested and placed in an identity parade. He was picked out by a rather distraught woman as the man who had raped her earlier that evening. Fortunately for Thompson the time of the rape coincided with his appearance on television, where, ironically, he had been debating the fallibility of eyewitness memory. Further investigation revealed that the woman was raped while she watched the TV show and she had confused her memory of the rapist with that of Thompson.

There may be little we can do about people’s poor memory, but we can at least try to ensure that when an eyewitness cannot correctly recognise the perpetrator of the crime they saw, they don’t pick out someone who is innocent. We need to understand the factors that cause people to identify someone wrongly, rather than reporting that they do not recognise the perpetrator in the identity parade. To some extent, variations in the line-up procedure address this – simply reminding the witness that the perpetrator ‘may not be present’ helps (for example, if the police had arrested the wrong person then the real perpetrator would not be in the line-up). Similarly, if the members of the identity parade are seen one at a time rather than all being present simultaneously then false identifications are reduced. It’s likely that this is because a simultaneous line-up encourages identification of the individual that best matches the memory of the perpetrator (i.e. the one that ‘looks most like’ the perpetrator). In the same way, unless he or she is specifically reminded otherwise, the witness may believe that the perpetrator is definitely present and pick the best match.

Characteristics of the eyewitness themselves also have an effect. For example, in laboratory tests children are more likely than young adults to identify wrongly a member of the identification parade as being the perpetrator. Havard and Memon (2013) devised an ingenious procedure to investigate this:  as well as the normal line up structure, an additional “person” – actually a silhouette called the “mystery man” – was included and the children were told that if they didn’t see the man who committed the crime, they were to pick the mystery man. This manipulation resulted in a massive drop in false identifications, from 75% to 40% in line-ups where the perpetrator was not present. Moreover there was no reduction in correct identifications when the perpetrator was present. However, 40% is still a worryingly high false identification rate and in a real situation could contribute to a miscarriage of justice.  Older eyewitnesses also tend to make a high number of false identifications in lab tests, which is perhaps even more of a concern. If they also do so in real situations where they may be seen as reliable trustworthy witnesses then their evidence, albeit given in good faith, may result in harm to innocent parties.

How are we to reduce harm and promote justice, then? Ensuring that best practice, informed by psychological research, is followed in the structure and conduct of identity parades is vital. But so is bearing in mind the evidence that memory is more fragile than we might imagine or hope, especially for unfamiliar faces.   Mistaken identifications that lead to wrongful convictions can be as unjust as not solving the crime at all.

Helen Kaye, Deborah H. Drake & Graham Pike, International Centre for Comparative Criminological Research, The Open University.