Post #243

950 words; 4 minutes to read

This post was authored by graduate student Michelle Reinink based on work done by Dr Jamal Mansour  and colleagues at the University of Lethbridge.  


Imagine that you are walking late at night. You hear footsteps behind you and as you turn, someone hits you, grabs your wallet and runs off. You report to the police and describe the attacker. Some days later, the police ask you to look at a lineup for the person they suspect attacked you.

It’s has been some time since the crime occurred. You select someone confidently stating, “that’s them, I’m 100% certain,” and that you would “never forget his face.” Later, you hear that someone else was caught after a series of similar incidents and that person admitted to robbing you as well. When you see their picture, they do not look a lot like the description you gave. You identified an innocent person, and this innocent person could have been imprisoned based on your identification.

Unfortunately, cases like this are more frequent than we might assume.

Eyewitness Unreliability

Eyewitnesses are an integral part of the criminal justice system. However, eyewitnesses can make mistakes because memory isn’t perfect. According to the Canadian Registry of Wrongful Convictions, in 25 out of the 89 wrongful convictions cases eyewitness identification errors played a role. The Innocence Project is an organization working to free individuals who have been wrongfully convicted. They report that just over 60% of clients they have worked with were imprisoned in part due to eyewitness errors, both intentional as well as unintentional.

Because of these errors, eyewitness reliability has been is a topic of research that has revealed numerous factors that bring into question the accuracy of eyewitness evidence.

What Affects Eyewitness Memory?

A major contributing factor to unintentional eyewitness errors is our ability to remember. A common belief is that our memory is like a video camera that records everything we see in detail. In reality, our memory is subject to many kinds of manipulations and distortions. During the event, factors that influence memory include stress, the presence of a weapon, and the severity of the crime influence memory. Even shortly after witnessing an event, memories can become muddled or altered due to leading questions, post-event information, and our own biases.

  1. Stress and Crime Severity: Witnessing a crime can be extremely stressful. Generally, research studies have found that witnesses remember information about a crime better if they are moderately stressed during that crime, compared to  when they experience low or severe stress, yet this can come down to personal differences or the type of crime committed. Severe crimes like murder or assault tend to cause severe levels of stress in victims and witnesses.
  2. Weapon Focus Effect: the presence of a weapon during a crime has been shown to lead to poorer eyewitness memory for the criminal because people tend to focus attention on the weapon. This may be because of the threatening or unusual nature of the weapon.
  3. Cross-Race Effect: Also known as the own-race or other-race effect, this shows that eyewitnesses tend to make more errors identifying someone of another race. This is believed to happen because we are better at differentiating faces of our own race either because we pay more attention to them or because we have had more experience with them.
  4. Leading Questions: The way questions are worded can impact the answers that an eyewitness will give. In a famous study, Loftus and colleagues asked participants to watch a short clip of a car accident. The participants were then asked to rate the speed they believed the car was going upon impact, but the word used to describe the impact varied. Some participants were asked “How fast was the car going when it smashed the other car”, and others were asked “How fast was the car going when it bumped the other car.” Participants rated the speed of the car as faster when the word “smashed” was used.
  5. Post-Event Information: Hearing information about the event after it was experienced can affect how we remember. When we hear false information and incorporate it into our memory, it is a misinformation effect. For example, imagine you witness a robbery. You see the perpetrator enter the store, go to the counter, and tell the clerk to give them the money from the cash register before leaving. After the event, another eyewitness mentions the clerk being assaulted, something you did not notice. But now you begin to think that the clerk was assaulted and feel like you can picture it. Later, when police ask you to describe the event, you mention an assault. You had incorporated this false information into your memory based on what another witness had (incorrectly) remembered.

 How Can We Improve Eyewitness Accuracy?

We cannot control every factor that affects an eyewitness’s accuracy and memory. However, some variables, called system variables, can be controlled. Wells and colleagues summarize research on eyewitness identification and identify best practices for obtaining reliable evidence. These include using double-blind procedures for lineups (where neither the officer presenting the lineup nor the eyewitness are aware of who the suspect is in said lineup), reminding eyewitnesses not to speak with one another about the event, selecting lineup non-suspect lineup members (fillers) so that the suspect does not stand out in the lineup, recording the identification procedure, not using showups (showing only an image of the suspect to the eyewitness), avoiding multiple identification procedures, and minimizing the amount of time between witnessing a crime and interviewing eyewitnesses where possible.

Given the importance of eyewitness testimony in securing convictions, police, lawyers and courts must do everything possible to ensure these identifications are accurate so as to avoid wrongful convictions.


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