Australasian Science - May 2016

(Nancy Kaufman) #1

E


yewitness misidentiication is the single greatest
cause of wrongful convictions in theUnited States,
having played a role in more than 70% of original
convictions later overturned by newDNAevidence
(www.innocenceproject.org).
This is consistent with a great deal of psychological research
using simulated crimes and lineups. This research shows that
our memories can be surprisingly fallible – we forget impor-
tant details of events, even whole events themselves, and we
remember things that have never happened.What’s worse, we
can make these mistakes even when we seem very conident
that our memories are correct.
Findings like these have cast doubt on the reliability of
eyewitnesses. Even when witnesses appear to remember some-
thing, or someone, strongly and with high conidence, they can
still be wrong.
Our research challenges this widespread view. Rather than
relying on laboratory studies, we were interested in the reliability
of eyewitnesses in actual police lineups and tested two impor-
tant conclusions drawn from laboratory research: that coni-
dence is not a good guide to accuracy, and that sequential lineups
are better than simultaneous lineups.
In a simultaneous lineup, the eyewitness is given all the
photos, usually laid out in a grid, and asked to identify the
person they remember committing the crime. In a sequential
lineup, each photo is presented one-by-one and the eyewitness
is asked to identify whether or not each photo is the culprit.
There is laboratory evidence that accuracy can be greater in
a sequential lineup than in a simultaneous lineup. This is
surprising, because more information is available to the witness
in a simultaneous lineup. While this could aid their decision-
making, it may instead make the decision more confusing.
The data for our study was collected by a member of our
team, William Wells, in collaboration with the Robbery Divi-

sion of the Houston Police Department, where 45 police oi-
cers had presented photo lineups to more than 700 eye witnesses
over a 12-month period. Each lineup included a photo of a
suspect that had been identiied by the police as possibly respon-
sible for the crime, as well as photos of ive innocent “illers”.
Half the lineups were presented simultaneously and the other
half were presented sequentially.
The lineups were conducted fairly – the administering oicer
was unaware which photo was of the suspect. Eyewitnesses who
identiied a photo as the culprit were asked to rate their coni-
dence on a three-point scale: low, medium or high conidence.
Our irst question was whether conidence was a reliable
indicator of accuracy. Unlike laboratory studies, we didn’t
know if the suspect in the photo lineup was innocent or guilty
so we weren’t able to measure accuracy directly. We therefore
approached this problem in two different ways.
First, because the suspect could be the culprit but none of the
innocent illers could be, high accuracy would be relected in a
high level of suspect identiication coupled with a low level of

18 | MAY 2016


How Reliable Is


an Eyewitness?


JOHN DUNN

Eyewitness identification of criminals is notoriously
unreliable, but a new study based on police records
has identified factors that can determine which
witnesses are accurate and which are guessing.

auremar/adobe
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