One of the failures in the criminal justice system is the conviction of a person for a crime they did not commit. This problem often exists because of unreliable eyewitness testimony. To correct this problem, scientists at the famous Salk Institute out of La Jolla, California, have identified a novel way of presenting a lineup to an eyewitness that could increase the chances that the correct suspect is identified and brought to justice. By using the science of perception, this new method could help reduce the number of innocent people sentenced to jail.
The Trouble with Eye Witness Testimony
“Our new lineup method reveals the structure of eyewitness memory, removes decision bias from the identification process, and quantifies the performance of witnesses,” states Professor Thomas D. Albright, co-author of the study. Why is this method so important? According to the Innocence Project, an organization that exonerates the wrongly convicted and prevents future injustice, 342 people have been exonerated due to DNA analysis as of 2016. Additionally, eyewitness misidentification has played a role in more than 70 percent of wrongfully convicted individuals (Innocence Project).
According to the American Psychological Association, experts believe many people think of memory as a kind of mental YouTube; when someone wants to recall an event, they find the right link and hit play. In reality, memories are not played back but are freshly reassembled every time they are recalled. This action makes them extremely susceptible to modification. Imagine a witness who hesitates when identifying a suspect from a lineup. The police officer says, “good job,” and the witness’s confidence grows. Later, the witness sees the culprit’s photo in the newspaper. A lawyer asks, “Do you remember if the suspect had pierced ears?” What develops is a false memory loaded with details that feel very real.
The good news is that research has focused on variables that influence a witness’s likelihood to identify the correct person. One fundamental factor is the way individuals are presented to the eyewitness during the lineup. Albright, an expert in the science of visual perception and recognition, reveals decades of research suggesting that people commonly misperceive visual events. Moreover, the memories of those events are continuously augmented and deteriorate over time (Science Daily).
The Simultaneous Method Vs. Sequential Method
The two most traditional methods used by law enforcement are known as simultaneous and sequential lineups:
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The simultaneous method includes having the eyewitness view six photographs of individuals at the same time.
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The sequential method includes having the eyewitness view six photos, one at a time.
The witness then identifies a suspect or rejects the lineup if no face matches their memory of the crime scene. However, according to the National Institute of Justice, some research has indicated that a sequential lineup produces fewer false identifications and fewer correct identifications. One study found that sequential lineups seem to make people less likely to make a choice. When they actually pick a suspect, they might be at greater risk of making the wrong choice. However, research that compares simultaneous and sequential lineups and the use of “blind” administrators have not been definitive.
The team at the Salk Institute explored a way to develop a new lineup method that would help predict the strengths of memories for each face and eliminate unconscious biases that shape decisions. “Traditional lineups reveal the top choice. However, the cause of the witness’s decision is vague. It may reflect strong memory for the offender, or it may mean that the witness was not very discerning. Our new technique overcomes that ambiguity by revealing the strength of recognition memory for all lineup faces,” states Albright.
The Method of Paired Comparisons
The team used a technique called the ‘method of paired comparisons’ to help correct eyewitness misidentification. This approach is similar to an eye exam. Like looking through pairs of lenses and stating which lens is clearer, the eyewitness is shown two photographs of individuals at a time. They then choose the one that looks more similar to the person they remember from the crime scene. The procedure generates an estimate of the strength of recognition memory for each lineup face. Statistical analysis of these memory strengths reveals the probability of correctly identifying the offender.
“Our methods derive from a branch of science called sensory psychophysics. Psychophysical tools are designed to reveal how properties of the physical world are ordered in the mind. Our approach allows us to measure how lineup faces are organized in the witness’s memory in terms of their similarity to the culprit,” states Sergei Gepshtein, first author of the paper. The method yields more significant information about the identity of the offender than previous methods. It also offers a quantitative index of certainty for individual eyewitnesses. “The conduct of a lineup is just one way to use our method. Another application is the selection of lineup fillers, which are faces of people known to be innocent. The fillers should not be too similar or too dissimilar to the suspect. Because the new system reveals the perceived similarity of faces, it can be used to optimize the choice of lineup fillers,” states Gepshtein.
The new method of paired comparisons holds much promise as a research and practical tool for investigating and prosecuting crimes. The team at Salk anticipates that the technique will soon be applied in real police casework.
