Current Human Rights beneficiary Innocence Project of Texas works to overturn wrongful convictions and educate the public about junk science. The pseudoscience parading as evidence in courtrooms around the country could fill a book, so I’ll restrict myself to one key issue: eyewitness identification. According to IPOT’s page on eyewitness identification, faulty eyewitnesses are involved in about 75% of false convictions overturned by DNA evidence.
People are not computers; human memory is not perfect We like to think of our memory as a video recording of past events, but memory is actually reconstructed and can be quite biased. We’re not as good at paying attention to people as we think; work on change blindness reveals that people can be substituted for one another or change clothes without attracting much notice (e.g., Simons & Levin, 1998). In the most famous example, misdirection causes people to miss a person in a gorilla suit walking by (Simons & Chabris, 1999).
Work by Elizabeth Loftus and her colleagues has shown that memories of an event can be changed by leading questions (e.g., Loftus & Palmer, 1974) and in extreme cases, completely false memories can be implanted (e.g., Loftus & Pickrell, 1995)!
With regards to eyewitness testimony in particular, a number of additional problems arise (see Wells, Memon & Penrod, 2006, for a review). These include the cross-race identification effect (misidentification is more likely when the perpetrator is of a different race than the witness), weapons focus effect (attention of the witness to a weapon limits the ability to remember the perpetrator), and the general negative effect stress has on memory.
The fact that memory is fallible is not problematic itself. The problem arises when jurors and legal professionals make life-altering decisions (e.g., verdicts, sentences, parole, etc.) as if memory were perfect. However, making some simple changes to lineup procedures can help quite a lot.
Solutions to the misidentification problem IPOT advocates for a number of procedures that reduce the likelihood of misidentification, including a bill in the Texas legislature (see also Clark, 2005; Wells & Olson, 2002; Wells, Memon & Penrod, 2006):
Blind administration: Refers to situations when the police officer conducting the lineup doesn’t know who the suspect is. Blind experimenters are standard for medical and psychological research, because experimenters can inadvertently influence human subjects.
Sequential arrays: Presenting photos or suspects one at a time forces witnesses to compare the picture to their memory of the suspect. When witnesses view several photos at once, they naturally compare the pictures to one another.
Limiting encouragement and prompts (e.g., “are you sure?” or “good”) from officers
Telling witnesses the target may or may not be present
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References Clark, S. E. (2005). A re-examination of the effects of biased lineup instructions in eyewitness identification. Law & Human Behavior, 29, 395–424. Loftus, E. F. & Palmer, J. C. (1974). Reconstruction of auto-mobile destruction: An example of the interaction between language and memory. Journal of Verbal Learning and Verbal Behaviour, 13, 585-589. Loftus, E.F. & Pickrell, J.E. (1995). The formation of false memories. Psychiatric Annals, 25, 720–725. Simons, D.J. & Chabris, C.F. (1999). Gorillas in our midst: sustained inattentional blindness for dynamic events. Perception, 28, 1059-1074. Simons, D.J. & Levin, D.T. (1998). Failure to detect changes to people in a real-world interaction. Psychonomic Bulletin & Review, 5,644–649. Wells, G. L. & Lindsay, R. C. (1980). On estimating the diagnosticity of eyewitness nonidentifications. Psychological Bulletin, 3, 776–784. Wells, G. L. & Olson, E. A. (2002). Eyewitness identification: Information gain from incriminating and exonerating behaviors. Journal of Experimental Psychology: Applied, 3, 155–167. Wells, G.L., Memon, A. & Penrod, S.D. (2006). Eyewitness evidence: Improving its probative value. Psychological Science in the Public Interest, 7(2), 45-75.