Abstract
Regarding police procedures with alcohol-intoxicated witnesses, Swedish police officers have previously reported inconsistent and subjective decisions when interviewing these potentially vulnerable witnesses. Most officers have also highlighted the need for national policy guidelines aiding in conducting investigative interviews with intoxicated witnesses. The aims of the two studies presented here were to investigate whether (1) police officers’ inconsistent interview decisions are attributable to a lack of research-based knowledge; (2) their decision to interview, as well as their perceptions of the witnesses’ credibility could be influenced by scientific research; and (3) police officers decision-making and perceptions of witness credibility are biased by pre-existing social norms. In two separate randomized online experiments, police professionals and recruits (Study 1, N = 43; Study 2, N = 214) watched a recorded fictive witness interview to which they were asked to rate the probability of interviewing the witness, the witness’ credibility, and to estimate the witness’ level of intoxication. Results showed that interview probability and perceived witness credibility were affected by witness intoxication level. While it cannot be stated definitely from the present research, these findings provided indications that police officers and recruits lacked research-based knowledge. Results also showed that interview probability, but not perceptions of credibility, was influenced by a research-based message. In line with research, interview probability for the most intoxicated witness increased after reading the message. Unexpectedly, neither interview probability nor witness credibility was affected by social norms. The current findings added to the legal psychology literature by showing that a breath alcohol concentration (BrAC) as low as .04% was enough for police officers and recruits to consider intoxicated witnesses less credible than sober witnesses. Findings also indicated that, despite the lower credibility assessment, police may have some understanding that these witnesses can be interviewed at low intoxication levels (i.e., around .04%). However, this willingness to interview intoxicated witnesses ceased at a BrAC lower than the levels where research has found intoxicated witnesses as reliable as sober witnesses (i.e., BrAC < .10%). Future directions for research and policy development as well as theoretical and practical implications of the present findings are discussed.
Highlights
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)
Planned simple contrasts showed that participants considered the highly intoxicated witness to be significantly more intoxicated compared with the sober witness
The present findings suggested that police officers and police recruits might make decisions in the absence of research-based knowledge, leading to inconsistent interview decisions, as well as their ability to deem witnesses as credible
Summary
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, 2021, 2022; Monds et al, 2021a) and lay people (Evans and Schreiber Compo, 2010; Monds et al, 2021b) that intoxicated witnesses are less credible than sober witnesses. Despite the known importance of obtaining information from witness interviews, police officers have reported inconsistent decisions to interview intoxicated witnesses and report varying procedures of engaging with them (i.e., waiting until witness is sober vs. interviewing immediately; Evans et al, 2009; Crossland et al, 2018; Monds et al, 2021a; Hagsand et al, 2022)
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