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Beyond the legal limit? The Effects of Real-World Intoxication Levels
on Eyewitness Recall
Robert GonzalezChristopher Altman, M.S.
Nadja Schreiber Compo, Ph.D.
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
Alcohol and Memory
Many of the initial studies examined alcohol’seffect 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
Alcohol & Eyewitness
Memory
Few researchers have examined theeffects of alcohol on eyewitness memory
Memory measures
Memory for the event: free, cued recall
Memory for faces: identifying the perpetratorin the video
Alcohol & eyewitness memory for events
Findings
Effects on quantity
Fewer effect onquality
Little to no effect(e.g., Flowe et al.,
2015; La Rooy, 2013)
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
Participants not intoxicated enough?
The Present Study
Most lab based studies: Around .08 BAC
Witnesses encountered by the legalsystem: .11+ (e.g.,Evans, SchreiberCompo, & Russano, 2009)
Precision a factor?
Aim:
Examine eyewitness memory for eventsat higher BAC levels
Approached bar patrons at a local bar"Research on alcohol & behavior"
Methods
Taken to a separate secluded testingroom so that participants could hearstimulus materials
Intoxication measurements:Handheld breathalyzer (S80 Pro Edition)
Field Study
Video of convenience store
robbery (staged) 2.5 minute video
BAC
Witness interview
Procedure
Perpetrator & 3 bystanders
Enter the store at different times
Method Cont.
1 free recall question and 1 follow-up probe9 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.
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%
BAC Levels
3 intoxication groups
Mild: .000 - .079 N = 47
Moderate: .080 - .130N = 22
High: .131+N = 16
ANOVAMild 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
RegressionIntoxication level was a significant predictor for witness quantity F(1,83) = 14.77, p = .000, R2 = .15, b = -165.03, B = -.389
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
RegressionIntoxication level was a significant predictor of witness accuracyF(1,83) = 14.164, p < .01, R2 = .14, B = -.38
ANOVA
Witness Quality - Precision
Mild vs. Mod vs. High Intoxication
Mild: M = 1.55Moderate: M = 1.57High: M = 1.35
(F(2,82) = 3.163, p < .05
RegressionIntoxication level was a significant predictor of witness precisionlevel: F(1,83) = 4.76, p = .032, R2 = .054, B = .23
ANOVA
Limitations
Intoxication level was not manipulated
Precision scoring only on a scale from 1-3
Data collapsed across open-ended and cued recall
Discussion
Imitating real-world intoxication levels yields significant decreasesin the amount and accuracy of witness information reported
Moderately intoxicated witnesses also adjusted their precision leveland reported with less precision than sober/mildly intoxicatedwitnesses
Strongest effect of alcohol above the average BAC of real-worldintoxicated witnesses (.11) as reported by law enforcementinterviewers (Evans et al., 2009)
Mixed and null results in the literature may be explained by therelatively low BACs
