1) The study examined the effects of real-world intoxication levels on eyewitness recall of a staged convenience store robbery. 2) It found that witnesses with higher blood alcohol content (BAC) levels of .131 or more recalled significantly less information that was also less accurate compared to those with mild (.000-.079 BAC) or moderate (.080-.130 BAC) intoxication. 3) Witnesses with high BAC levels also tended to report details with less precision than those with lower BAC levels. The findings suggest that intoxication above a .11 BAC significantly impairs eyewitness memory.

1. Beyond the legal limit? The Effects of Real-
World Intoxication Levels
on Eyewitness Recall
Robert Gonzalez
Christopher Altman, M.S.
Nadja Schreiber Compo, Ph.D.

2. Witness testimony often constitutes a central piece of
evidence in legal investigations.
Intoxicated witnesses encountered by the legal system
(Evans et al., 2009; Palmer et al., 2013)
Witness credibility challenged
Introduction

3. Alcohol and Memory
Many of the initial studies examined alcohol’s
effect on memory using word lists, digit spans, etc.
Impairs memory
(e.g., Bisby, Leitz, Morgan, & Curran, 2010)
No effect on memory
(e.g., Garfinkel, Dienes, & Duka, 2006)
Alcohol improves memory
(e.g., Jarosz, Colflesh, & Wiley, 2012)
Mixed findings
Research

4. Alcohol & Eyewitness
Memory
Few researchers have examined the
effects of alcohol on eyewitness memory
Memory measures
Memory for the event: free, cued recall
Memory for faces: identifying the perpetrator
in the video

5. Alcohol & eyewitness memory for events
Findings
Effects on quantity
Fewer effect on
quality
Little to no effect
(e.g., Flowe et al.,
2015; La Rooy, 2013)

6. Typical Lab Study Procedure
Sober or Intoxicated
Witness event
(staged or mock)
BAC measures and
Interview
Quantity: total number units reported
Quality: rate of in/accurate statements reported
No distinction between precision levels:
(e.g., Handgun = 1 accurate unit vs. 44 Magnum= 1 accurate unit)
Outcome Measures
BAC .08

7. Participants not intoxicated enough?
The Present Study
Most lab based studies:
Around .08 BAC
Witnesses encountered by the legal
system: .11+ (e.g.,Evans, Schreiber
Compo, & Russano, 2009)
Precision a factor?
Aim:
Examine eyewitness memory for events
at higher BAC levels

8. Approached bar patrons at a local bar
"Research on alcohol & behavior"
Methods
Taken to a separate secluded testing
room so that participants could hear
stimulus materials
Intoxication measurements:
Handheld breathalyzer (S80 Pro Edition)
Field Study

9. Video of convenience store
robbery (staged) 2.5 minute video
BAC
Witness interview
Procedure
Perpetrator & 3 bystanders
Enter the store at different times

10. Method Cont.
1 free recall question and 1 follow-up probe
9 cued questions
(e.g., What did the perpetrator do when he entered the store?)
Scoring
Recall
Interview transcripts were broken down into units of information
Each units was scored for accuracy (inter-rater reliability >.90)
Units scored for precision on a 1-3 scale:
1 = not precise (e.g., “a gun”)
2 = moderately precise (e.g., “a revolver”)
3 = very precise (e.g., “ an 44 Magnum”)
vs.

11. Participants
N = 85
Age range 19 – 55
Mean = 27.42 (7.30)
Gender
Males = 48.2%
Females = 44.7%
Did not report = 7.1%
Ethnicity
Hispanic = 47.1%
Caucasian = 30.6%
Other ethnicities reported = < 5%

12. BAC Levels
3 intoxication groups
Mild: .000 - .079
N = 47
Moderate: .080 - .130
N = 22
High: .131+
N = 16

13. ANOVA
Mild vs. Moderate vs. High Intoxication
Mild: M = 63.15
Moderate: M = 48.73
High: M = 39.81
(F(2,82) = 6.176, p < .01
Results: Witness Quantity of Information
Regression
Intoxication level was a significant predictor for witness quantity
F(1,83) = 14.77, p = .000, R2 = .15, b = -165.03, B = -.389

15. Witness Quality of Information
Mild vs. Mod vs. High Intoxication
Mild: M = 88%
Moderate: M = 89%
High: M = 72%
F(2,82) = 10.90, p < .01
Regression
Intoxication level was a significant predictor of witness accuracy
F(1,83) = 14.164, p < .01, R2 = .14, B = -.38
ANOVA

17. Witness Quality - Precision
Mild vs. Mod vs. High Intoxication
Mild: M = 1.55
Moderate: M = 1.57
High: M = 1.35
(F(2,82) = 3.163, p < .05
Regression
Intoxication level was a significant predictor of witness precision
level: F(1,83) = 4.76, p = .032, R2 = .054, B = .23
ANOVA

19. Limitations
Intoxication level was not manipulated
Precision scoring only on a scale from 1-3
Data collapsed across open-ended and cued recall

20. Discussion
Imitating real-world intoxication levels yields significant decreases
in the amount and accuracy of witness information reported
Moderately intoxicated witnesses also adjusted their precision level
and reported with less precision than sober/mildly intoxicated
witnesses
Strongest effect of alcohol above the average BAC of real-world
intoxicated witnesses (.11) as reported by law enforcement
interviewers (Evans et al., 2009)
Mixed and null results in the literature may be explained by the
relatively low BACs

21. Questions?
Contact:
Robert Gonzalez at
rgonz415@fiu.edu
Thank you