Recent cases have come to the fore concerning faulty eyewitness ID raising increasing and continuing concern about the error rate of eyewitness ID. This concern dates all the way back to Janet Reno, Attorney General, who appointed a committee of mentalhealth professionals and attorney to evaluate the area of eyewitness ID. She was concerned about the alarmingly rising rate of error with eyewitness IDs. One of the outcomes of the committee's recommendations was to recommend that sequential lineups be conducted rather than all individuals being presented at one time as sequential was found to have significantly less error.
A recent story in the Los Angeles Times chronicled a man who was sent to prison for 15 years for a crime he did not commit. One of the eyewitnesses had said that he did not have glasses on at the time and was not sure of his ID. However, he notes that the police questioning resulted in his "telling them what they wanted to hear." Indeed, the authority of the interrogator can matter a great deal.
There is no way to estimate the frequency of mistaken IDs in actual cases. Several decades of research shows that mistaken ID is the single largest source of wrongful conviction. One study by Rattner (1988) had a sample of 205 cases. Review of the 205 cases of proven wrongful conviction noted that 52% of the cases were associated with mistaken eyewitness ID.
All psychologists agree on a three-stage model of memory (i.e., acquisition, retention, and retrieval). Many different factors can affect these three areas. Acquisition can be affected by learning disorders, disorders of attention, etc. Retention disorders can be caused by short-term memory impairment, brain dysfunction, depression, etc. Retrieval can be affected by cognitive and memory deficits.
The Yerkes-Dodson effect indicates that stress affects memory at very low and very high levels of arousal. Loftus found that memory efficiency dramatically affected negatively. Under stress, individuals watched a film and were either holding a teddy bear or there was what they thought was a cobra in a bag next ti them. They were shown a complex film event. The individuals with the stuffed cobra in a bag did far worse on complex event in terms of memory.
The question of why two people differ in an eyewitness account are affected by what are called event factors (i.e., exposure time, type of fact, frequency of observing an event, detail salience, violence of an event, stress, temporary biases, cultural expectations). Moreover, the weapon's effect wherein an individual focuses on the weapon of an assailant and the field of view out to the periphery as one goes out the periphery becomes increasingly error prone due to the fixation of focus on the weapon. This is especially important to assess in cases of individuals who are victims of violence. Stress hormones and glucocorticoids facilitate long-term memory storage.
The aforementioned Yerkes-Dodson effect was found in a study in which soldiers performed less well in combat versus in training, indicating the effects of stress.
The federal guidelines for eyewitness identification recommend that the lead investigator gage the state of mind of a witness, and that if a witness is distraught or anxious, there should be a delay of gathering of data about ID because of the state of mind of the witness.
A factor of general eyewitness ability is predictive of eyewitness accuracy (Boice, 1982). Some individuals are detail oriented and some are not. And some are more accurate in viewing and assessing an event and others are not.
Confidence malleability relates to individuals in the legal system who can contaminate the confidence of an eyewitness.
The largest factor contributing to false confession is mistaken eyewitness ID.
The trace alteration hypothesis indicates that more loosely integrated poor memory permits more trace intrusions from suggestive external sources.
The coexistence hypothesis indicates suggestive information more likely to coexist with memory from the original information if the original information is poor and has begun to disintegrate.
Factors affecting ability to encode and store information are: exposure duration, viewing distance, visibility, stress or fear, pressure of a weapon, adverse events, less time to view an event (meaning less time to encode the information and therefore a less accurate ID).
Faulty eyewitness ID is a problem that is not going to go away. One sees cases daily of wrongful conviction with faulty eyewitness ID frequently implicated. Education, health professionals, and experts should speak with one voice to judicial administrations about this runaway problem which most recently there was an estimate of 2000 wrongful convictions by the Innocence Project.
Michael J. Perrotti, Ph.D.
Certified Forensic Expert
Expert Witness Panel, San Bernardino Superior Court
Expert Witness Panel, Juvenile Court San Bernardino
Expert Witness Panel, Orange County Superior Court
Expert Witness Panel, Juvenile Court Orange County
Expert Witness Panel, Los Angeles County Superior Court
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Expert Witness Panel, Kern County Superior Court
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Rattner, A. (1988). Convicted but innocent: Wrongful conviction and the criminal justice
system. Law and Human Behavior, 12, 283-293.
Loftus, E. F. (1979). Eyewitness testimony. Cambridge, MA: Harvard University Press
Boice, R., Hanley, C. P., Shaughnessy, P., & Gansler, D. (1982). Eyewitness Accuracy:
A general observational skill? Bulletin of the Psychonomic Society, 204, 193-195.