apls conference-8

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

Questions?

Contact:

Robert Gonzalez at

rgonz415@fiu.edu

Thank you