Alcohol Intoxication, Impact on Eyewitness Memory

Alcohol consumption has a significant effect on eyewitness identification abilities, including the accuracy of perpetrator descriptions and identification accuracy in showups (an identification procedure where only one individual is shown to the witness) and lineups (an identification procedure where several individuals, usually six in the United States, are shown to the eyewitness). Understanding the effects of alcohol consumption on memory is critical for the police, investigators, prosecutors, defense counsel, judges, and jurors to be able to judge the veracity of statements and evidence that are put forward in cases where alcohol consumption was present.

The research to date that has examined the effects of moderate levels of alcohol intoxication on eyewitness [Page 12]memory and identification accuracy has found that intoxicated witnesses are less likely to be accurate in their descriptions of events and people but are just as likely as sober witnesses to make a correct identification decision. In addition, intoxicated witnesses may be more susceptible to suggestion and suggestive procedures than are sober witnesses. However, as research has suggested, this finding should not necessarily be taken to imply that intoxicated witnesses are always less reliable than their sober counterparts.

Ethyl alcohol, or ethanol, is a depressant that is produced by the fermentation of yeast, sugars, and starches and is most commonly found in beer, wine, and liquor. After it is ingested, alcohol is metabolized by enzymes in the liver. However, because the liver can only metabolize small amounts of alcohol at a time, the remaining alcohol is left to circulate through the body until it can be processed. Alcohol impairs judgment and coordination as well as attention level, and the more alcohol consumed, the greater the impairment. For example, in all states in the United States, the maximum level of blood-alcohol concentration (BAC) that is permitted to be under the “legal limit” for driving a motor vehicle is 0.08% (80 mg/dl). However, the effects of alcohol intoxication as described above are likely to be present at BACs much lower than is set by the legal limit.

Although scientists and researchers know that alcohol consumption causes reduced coordination and impaired judgment, the effects of alcohol intoxication on memory has received little attention from psychology and law researchers. One of the potential reasons for this is that previous research has focused on the effects of alcohol from a public safety perspective (i.e., setting legal limits for driving) and not from a victim or witness perspective. However, given that there are more than 450,000 violent crimes in bars and nightclubs every year in the United States (and therefore more than 450,000 victims/witnesses who are likely to have consumed at least some alcohol), research on this topic is extremely valuable. The general findings from the few research studies that have investigated the memory and identification abilities of intoxicated witnesses are described below after a brief review of alcohol decision-making theory and a description of the research methodologies that are used in this field of research.