Transcript The recall of vehicle licence plate details

THE VIRTUAL LICENCE PLATE (VLP) AND
ITS EFFECT ON EYEWITNESS
PERFORMANCE
David Emmett, Brian R. Clifford, Kelly Young,
Margarita Kandova, & Anita Potton
An update on ongoing research
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The problem
“Eyewitness recall of a licence plate can be the
backbone for case solutions.”
MacKinnon, O’Reilly & Geiselman (1990)
“In events such as hit and run accidents the time
available for viewing the licence plate is often
between 0.2 and 5 seconds.”
Al-Haboubi (1999)
“Witness reports are often incomplete distorted or
inaccurate.”
Fisher & Geiselman (1992)
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The potential
With licence plate details now computerised in most
countries, vehicle owner searches can be carried
out with great speed even on partial details.
Clearly, however, the more licence plate characters
that a witness correctly recalls then the greater is
the chance that a vehicle owner can be successfully
traced.
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Previous research
Despite the potential importance of licence
plate recall to criminal investigations, a
search of the extant eyewitness literature
prior to the commencement of this series of
studies, reveals almost a complete lack of
research into either the ability of
eyewitnesses to accurately recall the details
of vehicle licence plates or ways in which
such recall can be assisted
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MacKinnon, O’Reilly &
Geiselman (1990)
In a study using a series of still slides as stimuli in
which a 7 character Californian licence plate was
visible from various distances and with varying
clarity for a total of 45 seconds
together with immediate recall.
A control group correctly recalled 3.15 characters.
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MacKinnon, O’Reilly &
Geiselman (1990)
A second group, using a simulated licence
plate made from coloured cardboard with
removable vinyl alphanumeric characters,
achieved a non significant 7% increase in
characters recalled.
A third group, using the plate simulator and
the context reinstatement mnemonics of the
cognitive interview, achieved a significant
increase of 22% in correct character recall
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The current series of studies
A 21st century approach
The Virtual Licence Plate (VLP)
An electronic version of MacKinnon,
O’Reilly & Geiselman’s cardboard
simulator
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Brief history of this research
Early studies in this series concentrated on testing
the efficacy of the concept of using a Virtual Licence
Plate as a memory retrieval aid and then developing
the VLP to its maximum efficiency.
Significant improvement in eyewitness recall of
licence plates was seen using the VLP, especially in
conjunction with Mental Context Reinstatement.
The results of two early studies using VLP v.1 and v.2 were
reported in
Emmett, D., Clifford, B. R., Young, K., & Potton, A. (2004).
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Present state of the research
During the initial studies it was clear that the
use of the VLP in conjunction with MCR was
having a beneficial effect on the recall of
details of the crime scene beyond the licence
plate
Testing needed to be carried out using both the
‘old’ and ‘new’ style UK licence plates.
Would similar results be seen?
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The current studies
Two studies are presented
Both use VLP v.2 and MCR
Recall of licence plate and general crime
scene details tested
Old and new style UK licence plates
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A brief introduction to
VLP v.2
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VLP v.2
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‘New’ and ‘Old’ style plates
‘OLD’
‘NEW’
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Experiment 1
Stimulus
Video of staged child abduction with ‘old style’
licence plate clearly visible for 3 seconds
watched as individuals
Participants
104 undergraduates – naïve as to reason for
watching video
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Experiment 1
Delay
5 minutes – filled with Ravens Matrices to prevent
rehearsal
Recall
4 conditions – each conducted individually
Control – pencil and paper recall
VLP only – experimenter operated use of VLP
MCR only – individual MCR instructions
VLP + MCR – above two conditions in
combination
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Dependent Variables
Alphanumeric licence plate character
correctly recall in the correct location
Correctly recalled details of the crime scene,
other than the licence plate, through cued
recall
Errors are not being included in this
presentation
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Licence plate characters
group
Characters
correctly
recalled
control
3.35
VLP
4.12
p > 0.05
MCR
4.62
p < 0.05
VLP +
MCR
5.65
Significance
compared to
control
0 – 4 characters
correctly
recalled
5 -7 characters
correctly
recalled
Control
57.7%
42.3%
VLP
53.8%
46.2%
MCR
50.0%
50.0%
VLP + MCR
11.5%
88.5%
p < 0.001
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Recall of crime scene details
group
Items of
information
correctly
recalled
control
25.08
VLP
25.92
p > 0.05
MCR
31.92
p < 0.05
VLP + MCR
37.65
p < 0.001
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Significance
compared to
control
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Experiment 2
Stimulus
Video of staged street arrest with ‘new style’
licence plate clearly visible for 5 seconds
watched as individuals
Participants
48 undergraduates – naïve as to reason for
watching video
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Experiment 2
Delay
5 minutes – filled with Ravens Matrices to prevent
rehearsal
Recall
3 conditions – each conducted individually
Control – pencil and paper recall
MCR only – individual MCR instructions
VLP + MCR – above two conditions in
combination
Dependent Variables - as before
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Licence plate characters
group
Characters
correctly
recalled
control
2.81
0–4
characters
correctly
recalled
5 -7
characters
correctly
recalled
Control
87.5%
12.5%
MCR
31.3%
68.7%
VLP + MCR
12.5%
87.5%
Significance
compared
to control
MCR
4.94
p < 0.01
VLP +
MCR
6.31
p < 0.001
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Recall of crime scene details
group
Items of
information
correctly
recalled
control
23.38
MCR
29.06
p < 0.05
VLP + MCR
35.63
p < 0.001
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Significance
compared to
control
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Discussion
licence plate details
Clearly in both experiments the use of the VLP and
particularly the use of the VLP in combination with
MCR has led to a marked increase in licence plate
recall.
In the case of the VLP plus MCR combination this
increase was significant in both experiments
Experiment 1- increase of 2.30 characters
Experiment 2 - increase of 3.50 characters
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Mental Context Reinstatement
Based upon the MCR mnemonic of the Cognitive
Interview
Witness mentally reinstates the context of the tobe-remembered event.
Technique applied with great care and intensity.
Encoding Specificity Hypothesis/Principle
(Tulving, 1976; 1983; Tulving & Thompson, 1973)
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VLP v.2
Increase in contextual cues that enable the witness to
bring to life their encoded memory trace. This is
particularly true of the characters that the witness
adds to the plate. Each character acting as a powerful
cue to the next.
Encouragement of witness to concentrate and
consider different ‘candidate combinations’ of
characters.
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VLP v.2
Part recognition task – Initial retrieval is a recall task
but then VLP provides a solid manifestation of that
recall enabling the witness to compare it directly
with the encoded trace in a recognition-like process.
Allows witness to access the power of the ‘change
order’ mnemonic of the CI.
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+ MCR
Clear that there is an additive if not multiplicative
effect when using VLP with MCR
MCR requires witnesses to focus on the target
licence plate and form a mental image of it. The VLP
enables the witness to bring that mental image into
concrete existence, to examine it, and through a
process of comparison with the encoded trace refine
it until as close a match as possible is achieved.
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Recall of crime scene details
Clearly in both experiments the use of the VLP in
combination with MCR has led to a marked
increase in the recall of crime scene details other
than the licence plate
.
This increase was significant in both experiments
Experiment 1- increase of 50.1%
Experiment 2 - increase of 52.4%
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Mental Context Reinstatement
The strongest effects are typically found in free recall, with
less strong effects in cued recall
Technique applied with great care and intensity.
Increases with MCR alone
Experiment 1- increase of 27.3%
Experiment 2 - increase of 24.3%
VLP v.2
Makes little apparent contribution on its own
Experiment 1- increase of 3.3%
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+ MCR
Clearly, as with the licence plate details there is
an additive if not multiplicative effect on general
crime scene recall when using VLP with MCR
How does a technique designed to improve recall of
licence plates also exerts a highly beneficial effect on the
recall of details of the event of which the licence plate
forms a part?
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+ MCR
The witnesses’ mind is focussed sharply
onto both the licence plate and the events
that surround it.
Increased interaction between witness and
experimenter leads to increased feelings of
involvement and motivation
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Next steps
Combining MCR with the VLP not only offers
investigators a powerful practical tool to assist
eyewitnesses in the recall a target licence plate
but also details of the event within which the
licence plate is embedded.
We now feel that the time is right to move out of
the lab and into live trials with the Police service
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Last question
What was the licence plate that you saw at the
beginning?
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