The cost to society of inaccurate eyewitness identifications is twofold, emphasizes psychologist Rod Lindsay, Ph.D., of Queens University in Kingston, Ontario. It's a double error," Lindsay says. "Not only are you convicting the innocent-or at least putting them through the process of having to get out of the situation-but the guilty are still out there doing the crimes."
It’s often said that the camera doesn’t lie.
But human memory does: The details of a memory can become
distorted, and events that occurred at different times can
become conflated with events that we imagined. As a result,
a witness to a crime forms a memory that may differ markedly
from the actual event. The likelihood of these so-called “retrieval
errors” increases if a witness is prompted—sometimes
deliberately, sometimes unintentionally—to fill in details
of an event that the witness may not have noticed at the time.
For example, suppose a woman who observed a fatal traffic
accident is rehearsing her testimony with a lawyer. The lawyer
says, “How fast was the car going when it went through
the red light?” At the time, she didn’t notice
the color of the light, but the way the lawyer phrased the
question plants the suggestion in mind that the car ran a
red light. As a result, the woman may form an image of the
traffic light in her mind’s eye—an image she didn’t
really see at the actual event.
Later if she practices her testimony and retrieves the accident
from her memory, the image of the red traffic light is replayed,
too. Each time, it becomes more strongly embedded in memory.
She may grow more and more confident that a car running a
red light was part of the actual event.
In the courtroom, this woman may give inaccurate eyewitness
testimony, although she didn’t intend to mislead the
court. If she seems credible to a jury, her testimony might
send an innocent person to jail. The bottom line: Memory does
not always consistently distinguish between the parts of a
story that are real and the elaborations or embellishments
that were added later.
Memory and the courts
There remains a disconnect between scientific understanding
of memory and the popular perception, Lindsay notes. “It’s
old news to psychologists that memory is constructive, that
there are inferences involved in memory, but the rest of the
world doesn’t necessarily understand that,” he
says. “People know there are errors, but I don’t
think they really understand how easy it is to elicit those
errors and how systematic the errors can be.”
Lindsay says that if you weigh in all the studies done to
date on the accuracy of eyewitness identifications conducted
with standard lineups, the accuracy rate is about 60 percent.
That means four out of every 10 eyewitness ID’s are
Lindsay and other researchers have developed improved procedures
that can significantly reduce these errors. These include
sequential line-ups, where witnesses see faces one at a time
rather than choosing one out of a small set. Another procedure
is double-blind lineups, in which neither the witness nor
the police officer handling the lineup knows who the prime
suspect is. This prevents the officer from inadvertently tipping
the witness off to make the "correct" choice, or
from giving confirmatory feedback ("Good, you got him")
that may affect the witness's memory—like the woman
"recalling" the red light in the example above.
Lindsay is certain of the need for double-blind lineups and
other reforms in the justice system. "Double blind is just
something that should be done automatically," he says. "It's
amazing to think that scientists have said for years that
they couldn't trust themselves not to bias the data. You do
double-blind testing with placebos for drug studies because
you can't trust yourself not to influence the results. We
knew that 80 years ago, and yet nobody ever transported it
to police investigations and the influencing of witnesses."
Lindsay and his colleagues are testing a new procedure that
could reduce mistaken identifications even more so than a
double-blind sequential lineup. In the technique, photographs
of the suspect and five innocent "foils" are used to construct
a sequential lineup. But instead of just showing faces, the
witness sees only the head of each person in the lineup, then
sees photos of just the bodies from the shoulders down with
the faces electronically edited out, and finally hears a sample
of each person's voice.
In preliminary testing, witnesses who can correctly identify
the face, body, and voice of the person are considerably more
accurate than witnesses who can only correctly identify one
of these factors (typically the face). In fact, when witnesses
chose the face, body, and voice, the identification is virtually
always accurate. This kind of "multiple identification" technique
is still in the research stage, but it does suggest that innovative,
new procedures-if adopted by police-could significantly cut
down on the number of inaccurate eyewitness identifications.
Research on eyewitness identifications highlights the fact
that memory does not accurately record events-even extraordinary
events like murder and rape. So next time you are in a heated
argument with a friend or spouse over something you supposedly
heard him say or saw her do, slow down for a second and think
of the dozens of people who have sat in jail for years until
new evidence revealed what psychologists and neuroscientists
have known for years: that seeing is indeed believing, but
what you "remember" isn't necessarily what actually happened.
"Eyewitness Testimony," by Gary
L. Wells and Elizabeth A. Olson. (Annual Review of Psychology,
2003, Volume 54, pp. 277-295).
"Distorted retrospective eyewitness reports as
functions of feedback and delay," by Gary L.
Wells, Elizabeth A. Olson, and Steve D. Charman. (Journal
of Experimental Psychology: Applied, 2003, Volume 9, Number
1, pp. 42-52).