Prior to viewing a lineup, eyewitnesses to crimes are often given various instructions by lineup administrators. Among these is the appearance-change instruction, which is used to inform the eyewitness that the criminal’s appearance in the lineup may be different from his or her appearance at the time of the crime. Generally, this alteration in appearance would be the result of features that might have changed over time (such as head or facial hair). This instruction is especially likely to be given, and is presumed to be most beneficial, if a significant period of time has passed between the crime and the lineup or if the suspect’s appearance is somehow at odds with the witness’s description of the criminal. Although frequently administered in an attempt to increase identifications of the criminal, preliminary research suggests that the appearance-change instruction does not increase correct identifications but instead increases false identifications of innocent lineup members.
Eyewitness Evidence: A Guide for Law Enforcement (a set of guidelines distributed to all law enforcement agencies across the United States) recommends that lineup administrators instruct a witness that “individuals present in the lineup may not appear exactly as they did on the date of the incident because features such as head and facial hair are subject to change” (p. 32). Although recommended, this instruction is not mandatory; consequently, various police departments and individual lineup administrators may word the instruction differently or may omit it altogether. The purpose of this instruction is to ensure that the witness does not fail to identify the criminal simply because the witness does not appreciate that the criminal’s appearance might have changed since the crime. Therefore, it is implicitly assumed that administering the appearance-change instruction will lower witnesses’ expectations that the criminal’s appearance in the lineup will exactly match his or her appearance at the time of the crime. This should, in turn, increase the probability of correctly identifying the actual criminal when the criminal is in fact in the lineup.
Empirical research on the effects of the appearance-change instruction is scarce. Preliminary studies suggest, however, that the instruction may not be as beneficial as previously assumed. Although it has been shown experimentally that witnesses who receive an appearance-change instruction do make more lineup identifications, this did not result in an increased number of correct identifications. Instead, the appearance-change instruction was shown to increase the number of incorrect identifications of fillers (i.e., lineup members who are known to be innocent) without increasing the number of correct identifications of the criminal. Although it is uncertain whether these findings will be replicated by future studies, they do nonetheless challenge the basic assumption underlying the use of the appearance-change instruction. Such an increase in false identifications without a concomitant increase in correct identifications means that lineup identifications made following an appearance-change instruction were, as a whole, less accurate than identifications made without an appearance-change instruction. Additionally, the appearance-change instruction has been shown to increase the length of time it takes witnesses to make an identification and to decrease the confidence with which witnesses report making an identification.
Although it is as yet not known why the appearance-change instruction increased false identifications without a concomitant increase in correct identifications, two hypotheses have been advanced. Both are predicated on the assumption that a lineup identification occurs when the similarity of a lineup member to the witness’s memory of the criminal surpasses a minimum level.
The first hypothesis is that the instruction may simply lower a witness’s decision criterion (the minimum level of similarity needed to result in an identification). Witnesses who are given an appearance-change instruction might conclude that due to possible appearance change they should not expect a high degree of similarity between the criminal in the lineup and their memory of the criminal. However, because even innocent lineup members may bear some moderate resemblance to the criminal, if a witness’s decision criterion is low enough, even these innocent people may be falsely identified.
The second hypothesis that explains the effects of the appearance-change instruction is that the instruction may lead witnesses to mentally alter various facial features of the lineup members. For example, witnesses may imagine what the lineup members would look like with different facial hair, different hairstyles, or a chubbier face. If witnesses mentally alter the various lineup members’ appearance in an effort to match the lineup members to their memory of the criminal, then even innocent lineup members may come to resemble the actual criminal. Thus, the appearance-change instruction would make it even more likely that the similarity between an innocent lineup member and the criminal surpasses the witness’s decision criterion, thereby leading to a false identification.
Whether the effects described here are replicable and whether they generalize across variations in the wording of the appearance-change instruction, across different witnessed events, and across various other lineup manipulations remain open empirical questions. A greater understanding of the effects of the appearance-change instruction, and the explanation of those effects, awaits further research.
- Charman, S. D., & Wells, G. L. (2007). Eyewitness lineups: Is the appearance-change instruction a good idea? Law and Human Behavior, 31, 3-22.
- Douglass, A. B., & Gerety, M. (2005). Eyewitness accuracy as a function of lineup instruction and expectation. Unpublished manuscript.
- Technical Working Group for Eyewitness Evidence. (1999). Eyewitness evidence: A guide for law enforcement. Washington, DC: U.S. Department of Justice, Office of Justice Programs.
Return to the overview of Eyewitness Memory in Forensic Psychology.