Radio Iowa
09-21-06
I-S-U expert says Missouri crime points out eyewitness problems
by Stella Shaffer
A sensational stolen-baby case in Missouri has ended today with charges against
a woman accused of injuring a young woman and taking her newborn child.
Images of the suspect were distributed nationwide, but Iowa State University
Psychology Professor Gary Wells says eyewitness accounts are frequently
flawed
"The study of memory is really the oldest area of scientific psychology," says
Wells, so recently the field has been looking at what eyewitnesses can remember
from crimes and seeing what can be done to improve that. He says,
"Eyewitnesses are not performing very well."
Wells says when people try to recall the face of a suspect or someone else
they've spotted during a crime, they work with a professional sketch artist, or new
computer programs that help them choose from a wide variety of models of each
facial feature.
"When you do that, you end up with something that looks like a real face." The
problem is, he says, that it often doesn't much resemble the face of the person
they're trying to identify.
It's a problem for police and the legal system, he says: "If they release a
composite they might be giving solace to the real perpetrator who might look at it,
and say boy, they'll never find me based on that." He says the reason a picture
made from memory isn't very good is because you don't look at a person the way
a camera or a computer might.
When you see somebody's face, you don't exactly remember what the nose
looked like, the eyes looked like, etc. Instead, says Wells, "Face-processing is
more holistic." You have an overall impression. He says often several people will
be eyewitnesses to an event, and that turned out to be the key to a solution -taking their varying impressions of the suspect's face and morphing them
together in a computer program.
Morphing is just "a form of averaging," he explains, so all you're doing is taking
the four different impressions of a face and using computer technology,
"averaging them at the pixel level." He says his research found that doing that
averaging will produce a new face that resembles the real person a lot more than
any of the original composite pictures did. Wells says that holds promise of
creating more useful eyewitness pictures for a criminal investigation.