Validity of Eyewitness Testimony

Validity of Eyewitness Testimony

Validity of Eyewitness Testimony

In today's court system one of the strongest pieces of evidence, or that most commonly accepted as fact by a jury, is eyewitness testimony. When correct, eyewitness accounts can aid in the conviction of many guilty people. However when it is incorrect, eyewitness testimony can do severe damage. Researchers have found that “more innocent citizens are wrongfully tried and convicted on the basis of eyewitness evidence in Great Britain and North America than by any other factor within the legal system” (Smith, Stinson, & Prosser, 2004, p. 146). Even with the recent background of cases being overturned on the basis of DNA evidence many years after conviction, eyewitness identification is considered by most jurors and judges as the most persuasive sort of evidence. DNA testing contributed to the exonerations of over 100 people in the United States who were on death row. In 80-90% of these cases, eyewitnesses were a key factor in the conviction (Smith, Stinson, & Prosser, 2004). This poses the question of how valid is eyewitness memory. It does indeed appear to be unreliable. So, therefore, the judge and jurors should be alert to the possibility of mistaken identification resulting not only from suggestive law enforcement identification techniques, but also from the inability of human memory. One possibility is to educate the jurors and judge about the problems surrounding eyewitness testimony. Eyewitness testimony can be flawed simply because of the normal and natural memory processes that occur whenever people acquire, retain, and attempt to retrieve information (Loftus, 1979). The validity of eyewitness identification depends on numerous variables. Eyewitness testimony validity can be affected by perception and memory, the weapon focus effect, cross race identification effects, eyewitness confidence and accuracy, and questioning techniques.

Perception and Memory

Identification by eyewitnesses is not always reliable evidence. The human brain is simply not constructed in such a way as to function as a video camera in which one can hit instant replay. There are three stages involved in remembering an important event. The first stage is the acquisition stage in which the information is encoded into a person’s memory system. The second stage is the retention stage which is the period of time that passes between the event and the recollection of a particular piece of information. The third stage is called the retrieval stage. In this stage the person recalls the stored information (Loftus, 1979). Once information has been stored in a witness’s memory some of it may remain there unchanged while some may not.

Many things can happen to a witness during the crucial retention stage of memory. Witness’s may talk with others about the event, overhear conversations, or read a newspaper article pertaining to the event. All of these situations can bring about powerful changes in the witness’s memory (Loftus, 1979). During the acquisition stage there are also many factors that affect a witness’s ability to perceive. One factor is stress. The Yerkes-Dodson law explains that “strong motivational states such as stress or other emotional arousal facilitate learning and performance up to a point, after which there is a decrement” (Loftus, 1979, p. 33). An increase in stress tends to produce a narrowing of attention. Therefore, under high stress people concentrate more on a few features of their environment while paying less attention to others (Loftus, 1979).

Weapon Focus Effect

Weapon focus is a factor affecting the validity of eyewitness testimony. Weapon focus is defined as “the visual attention that eyewitnesses give to a perpetrators weapon during the course of a crime” (Steblay, 1992, p.414). This phenomenon expects that the weapon used during the crime will draw attention which decreases the ability of the eyewitness to adequately encode and later recall important details. An explanation may be that “the threat that someone may be injured or killed increases the witness’s level of emotional arousal, which then reduces his or her attentional capacity” (Pickel, 1999, p.300). Studies on the weapon focus effect usually included a weapon’s presence or absence during the crime as the independent variable and the individual’s later attempt to identify the perpetrator in a lineup as the dependent measure (Steblay, 1992). The researchers hypothesized that correct identifications will be greater in the condition in which the weapon