Memory and credibility perceptions of alcohol and other drug intoxicated witnesses and victims of crime

Abstract

Research into juror perceptions regarding the impact of intoxication on eyewitness memory and credibility is scarce for substances other than alcohol. However, jurors are frequently told to draw on their personal beliefs and experience with intoxicating substances to infer their impact on the case. It is therefore important to investigate laypeople's perceptions regarding witness and victim intoxication across a range of substances, and whether these perceptions are associated with substance familiarity. Participants (n = 470) completed a survey assessing familiarity and use of different substances, as well as perceptions regarding effects on the memory and credibility of intoxicated victims and witnesses. While participants most frequently reported believing that alcohol, hallucinogens, and polysubstance use of alcohol and cannabis have large negative effects on memory, they more frequently reported that they do not know the extent to which cannabis and cocaine affect memory. In addition, attitudes were found to vary based on substance familiarity.Differences with respect to the perceived impact on memory and credibility of various substances have relevance to court proceedings, particularly in terms of voir dire procedures and whether an expert witness may be required to educate the court on the impacts of different forms of intoxication.

Juror Perceptions of Bystander and Victim Intoxication by Different Substances

“…The finding that witnesses intoxicated by amphetamines were perceived more negatively (i.e., lower credibility/cognitive competence) than sober witnesses is consistent with previous survey data. For instance, respondents in the study by Monds et al (2022b) believed that witnesses intoxicated by amphetamines would have poorer memories than sober witnesses and that amphetamine intoxication would negatively impact witness credibility. Therefore, the effect of witness amphetamine intoxication on perceptions might be driven by our participants' beliefs about how amphetamines impair a witness' ability to give accurate testimony, which in turn has a detrimental impact on credibility.…”

“…The lack of an effect of cannabis intoxication on witness perceptions might reflect laypeople's uncertainty regarding the effect of cannabis on memory. For example, Monds et al (2022b) found that while respondents believed that a cannabis-intoxicated witness would be less credible than a sober witness, these same respondents also stated that they were uncertain about how cannabis would affect eyewitness memory. Perhaps our participants were also generally uncertain about how cannabis influences memory (as per previous research), and thus were unsure about the credibility of a cannabis-intoxicated versus sober witness in the current study.…”

“…While it is unclear how intoxication by these substances would affect bystander and victim credibility in court and the outcome of trials, some preliminary research may offer some insights. Monds et al (2022b) surveyed undergraduate students about alcohol, cannabis, and other substances they were familiar with (e.g., amphetamines) in relation to perceptions of witness memory and credibility. Most participants believed that alcohol and amphetamines would have a negative effect on memory but were unsure about the effect of cannabis on memory.…”

Police Decision-Making in the Absence of Evidence-Based Guidelines: Assessment of Alcohol-Intoxicated Eyewitnesses

“…In the past, the alcohol and memory literature have often found evidence of detrimental memory impairments being caused by alcohol-intoxication (e.g., Parker et al, 1976;Mintzer, 2007). This provides a rationale for the prevalent perception among legal practitioners (Kassin et al, 2001;Evans et al, 2009;Crossland et al, 2018;Hagsand et al, 2021Monds et al, 2021a) and lay people (Evans and Schreiber Compo, 2010;Monds et al, 2021b) that intoxicated witnesses are less credible than sober witnesses. However, the effects of memory impairments caused by alcohol-intoxication have often not been replicated within the applied legal context of eyewitness memory (see Altman et al, 2019, for a review).…”

The effects of alcohol and co-witness information on memory reports: a field study

“…Alcohol intoxication in witnesses and victims is common (Crossland et al 2018;Evans et al 2009;Monds et al 2021) and such witnesses often play a comparable role to their sober counterparts in criminal investigations (Palmer et al 2013). Both were just as likely to make a suspect ID and to provide a suspect description.…”