Eyewitness Identification -expert Testimony
| Publication year | 1979 |
| Pages | 1438 |
| Citation | Vol. 8 No. 8 Pg. 1438 |
1979, August, Pg. 1438. Eyewitness Identification -Expert Testimony
Most criminal defense attorneys know very well that in eyewitness identification cases, "seeing is believing"---the eyewitness testifies that he saw the defendant, and the jury believes him.(fn1) Although the dangers of so-called "eyewitness-identification" have been widely acknowledged and discussed in legal and scientific communities for years; few, if any methods have been accepted by the Judiciary which would significantly reduce the possibility of conviction of innocent persons as a result of unreliable eyewitness identification.(fn2)
Because of the subtlety of the psychological phenomena surrounding the identification process, attempts at suppression of eyewitness testimony are generally ineffective. Cautionary jury instructions are often too little, too late. Juries generally do not have a real basis for properly using these instructions. The trial process provides the jury with no information regarding the mechanisms and shortcomings of eyewitness identification, and the jury remains unimpressed by the apparently legalistic jury instruction.
The eyewitness identification phenomenon involves complex psychological mechanisms which have been studied and documented, and, in some cases, this subject requires expert testimony to aid the finder of fact in evaluation of evidence. This article touches briefly on the processes and shortcomings of eyewitness identifications and suggests a legal framework for the use of the expert witness in this area.
The goal of expert testimony in the area of eyewitness testimony should be to point out, within the context of the case, the limitations of visual memory and recall. First it is necessary to consider the four-stage model of visual perception; then to briefly review some of the recent scientific evidence which relates to the four stages. The Visual Perception Model
There are four stages of visual memory processing:
1. Attention to and perception of the event;
2. Registration of the event in short-term memory;
3. Rehearsal of the event resulting in storage in long-term memory; and finally
4. Search and retrieval of the event from long-term memory.
The human memory system is not analogous to a videotape recorder where one can make a tape, store it almost indefinitely
and then come back and replay the original event. Instead, human memory is an active system. We select, process, and modify our visual images at each of the four stages of memory. Under certain circumstances, the selections and modifications can be substantial, leading to innaccurate identifications.
The general capacity of humans to recognize faces under the most ideal conditions is far from perfect. In a typical experiment, the research participant is shown twenty photographs for a few seconds each. He is then shown the identical faces again, but this time the photographs are embedded in a series of sixty other photographs. The task is to indicate, by saying yes or no, whether each photograph was used in the original study trial.
The accuracy rate for these studies typically ranges from 54 percent to 84 percent correct, with an average accuracy rate of 73 percent correct.(fn3) These studies impressively demonstrate even under ideal conditions of minimal psychological stress, minimal time between the original viewing and identification, and the mere identification of the photographs as those that were seen earlier that the accuracy rates are nowhere near the ideal of 100 percent accuracy that jurors seem typically to attribute to an eyewitness.
The basic questions here are obvious. Was it physically possible for the witness to have seen the suspect? Were the lighting conditions adequate? Did the eyewitness have an unobstructed view of the suspect? What is the visual acuity of the witness? If the witness is making an identification based on color does the witness have full color vision?
Assuming that it was physically possible for the witness actually to see the event or suspect, then we can begin looking at the psychological factors which limit the person's ability to store and retrieve visual information.
The first thing that happens after the image of an event hits the retina is that a representation of an image is transferred to short-term memory. Two things happen in short-term memory. First, the person makes a decision about whether the image and its details are important enough to store in long-term memory. If the decision is negative, then the image is not stored and will not be accessible for later recall. We are very selective in our everyday life. There is too much going on around us to store every detail of everything we see. Secondly, we decide how and where to store the image. Our memory is like a series of compartments or categories. We sort things out and place them into categories. The decision about where to place things is partially determined by the degree of importance of the event taking place and partially by the categories we have already used to store images. We are more likely to place things into categories that we have used before than we are to keep making up new categories for everything that comes along.
It is significant that at this stage it takes time to process the information and to make it ready for long-term storage. Perception psychologists have shown that if a person is distracted from thinking about an image immediately after being shown it, that person is not likely to be able to recall that image later on. The events surrounding a crime may place severe limitations on the ability of a witness to process information for long-term storage.
For example, in a life-threatening situation
the eyewitness may be concerned with protecting himself and with looking for ways to escape from the danger. His attention may be focused on the dangerous aspects of the situation, e.g., a weapon, and on the avenues of escape. If the brain is...
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