Investigating the Influence of Alcohol on Eyewitness Memory

Abstract

Whilst many eyewitness factors have been researched, one issue that has been largely overlooked until very recently is witness intoxication. Police officers in study 1 of this thesis, however, indicated that intoxicated witnesses are a common occurrence. With so little research there are no specific guidelines for the Criminal Justice System detailing the capabilities of intoxicated witnesses. To understand the abilities of these individuals, this thesis tested the theory currently underpinning intoxicated witness research: Alcohol Myopia Theory (AMT). This theory considers alcohol to particularly impair the recall of low, as opposed to high, salience details. Within this thesis, in contrast to previous research, but consistent with AMT, salience was determined by spatial location and semantic meaning, as opposed to information type or centrality. At low (MBAC=.06%) to moderate (MBAC=.09%) levels of intoxication, recall was not impaired when memory was assessed through free recall or a true/false recognition test. At higher intoxication levels (MBAC=.14%; study 3; a field study), contrary to the propositions of AMT, alcohol was only seen to impair free recall completeness, with high rather than low salience details suffering the greater deficit. In seeking to improve the recall of highly intoxicated witnesses, study 4 (a field study) adopted a modified Enhanced Cognitive Interview (ECI) procedure, applying the report everything and mental reinstatement of context mnemonics. The ECI, improved the correct recall, accuracy and completeness of moderately (MBAC=.05%) and severely intoxicated (MBAC=.14%) witnesses. With this thesis indicating that low to moderate intoxication levels are not particularly detrimental to recall, study 5 looked at juror perceptions of intoxicated witness credibility. The knowledge that the witness was intoxicated, rather than the actual testimony, resulted in poorer credibility ratings. In light of this thesis’ findings it is argued that AMT does not account for alcohols effect on eyewitness recall, but high levels of intoxication impair recall completeness but not accuracy. Based on this thesis it is recommended that police officers are provided with clear guidelines on how to deal with intoxicated witnesses, including interviewing with the ECI, even in the modified form. In addition, it is recommended that all parties in the judicial process be educated on the limited effect moderate intoxication has on witness recall, and that severe intoxication impairs recall completeness but not accuracy.

Date of Award	15 Aug 2017
Original language	English
Awarding Institution	University of Winchester
Supervisor	Wendy Kneller (Supervisor) & Rachel Wilcock (Supervisor)