No evidence that low levels of intoxication at both encoding and retrieval impact scores on the Gudjonsson Suggestibility Scale

The importance of the smallest effect size of interest in expert witness testimony on alcohol and memory

Memory experts are sometimes asked to evaluate the validity of accounts of witnesses, victims, or suspects. In some of these cases, they are asked what effect alcohol has on the validity of such accounts. In this article, we offer a guide on what expert witnesses can reliably say about how alcohol affects memory. We do so by resorting to effect sizes from previous studies and meta-analytic work, and address this novel question: Are these effect sizes meaningful in legal cases? More specifically, we argue that any determination of whether individual studies about alcohol and memory are practically relevant for legal cases, scientists must focus on the smallest effect size of interest. We make the case that a decrease or increase of only 1 detail, especially an incorrect detail, should be regarded as the smallest effect size of interest in this line of research. In line with this idea, we show that effect sizes in the alcohol and memory literature are often larger than this smallest effect size of interest. This finding is important because it implies that alcohol often exerts a practically relevant and meaningful detrimental effect on the reporting of both correct and incorrect details, which in turn negatively affects the validity of witness testimony.

Police–suspect interactions and confession rates are affected by suspects’ alcohol and drug use status in low-stakes crime interrogations

Background

Low-stakes crimes related to alcohol and/or drugs are common around the world, but research is lacking on police–suspect interactions of such crimes. A large proportion of these suspects are intoxicated during interrogations, and many may have substance use disorder, making them potentially vulnerable to interrogative pressure.

Methods

To address this lack of knowledge, the taxonomy of interrogation methods framework (i.e., 60+ interrogation techniques classified into five domains) and a common classification of question types (appropriate vs. inappropriate) were applied in the coding of written police interrogations. Two archival studies, one pilot (Study 1, N = 39) and one main study (Study 2, N = 97) analyzed police interrogations with suspects of alcohol- and drug-related crimes in Sweden.

Results

For both Study 1 and 2, suspects showed signs of alcohol and/or drug intoxication, hangover or withdrawal in more than 50% of all interrogations. In Study 2, additional coding indicated that suspects displayed signs of substance use disorder in 57% of the interrogations. The main results from both studies revealed a large number of direct questions asked by the police across all interrogations, and relatively little use of the strategic interrogation techniques from the taxonomy of interrogation methods framework. In fact, when it came to interrogation techniques, law enforcement used more confrontational techniques in their interactions with intoxicated suspects compared to sober suspects. Furthermore, suspects displaying signs of substance use disorder were significantly more cooperative and prone to confess than suspects without indicators of substance use disorder.

Conclusion

As the first novel study on low-stakes crime interrogations related to alcohol and/or drugs, the present study provides useful information about current Swedish interrogation practices and areas for improvement. The study results indicate that suspects displaying signs of intoxication or substance use disorder may be more vulnerable during police interrogations. This may in turn have the potential to inform the development of new interrogation policies. Due to the novelty of this research, more studies are needed, both on a national and international level, to examine interrogations in low-stakes crimes further.

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

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.

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

RATIONALE

Witnesses who discuss a crime together may report details that they did not see themselves but heard about from their co-witness. Co-witness information may have beneficial and harmful effects on memory accuracy depending on whether the information was correct or incorrect.

OBJECTIVES

Given the prevalence of intoxicated witnesses, it is imperative to understand how alcohol influences this effect.

METHODS

The present study asked pubgoers (n = 67) at varying levels of intoxication to recall a mock crime video after having also watched a video witness statement containing both correct and false information.

RESULTS

Increased intoxication was associated with decreased confidence, completeness and accuracy, but no increased tendency to report false information. Exposure to incorrect post-event information (PEI) can lead to the incorporation of incorrect information, whereas exposure to correct PEI increased accuracy, regardless of individuals' alcohol intoxication status.

CONCLUSIONS

Thus, whilst discussion and intoxication can negatively impact eyewitness memory, discussion may also have benefits for both sober and intoxicated witnesses.