Is it time to retire the police sketch?
Do you recognize this face? Most people probably
do, but try describing it from memory. Kind of like a taller head. Does he have brown
eyes? They’re not exactly deep-set. Green eyes? Bland features. I don’t remember like any
dimples or moles. Ben Affleck’s nose… Not flat but not super pointy either.
So this is the challenge faced by police sketch artists. They interview
victims and witnesses about a criminal’s face and their drawings go out to the public
with the goal of soliciting tips. Take a good look at that sketch. If that man looks familiar… If you have any information you’re asked to call metro crimestoppers. we wanted to find out how accurate these sketches
are, and if there might be a better way to put those memories onto paper. There really isn’t any good data on how
often a sketch helps police catch a criminal on the loose.
but by the looks of it, more often than not, they don’t achieve a very strong likeness.
There are certainly some notable exceptions, like this sketch made of Oklahoma City bomber
Timothy McVeigh. or cases where the suspect has a really distinctive
look. but mostly they’re kind of a shot in the dark.
In academic experiments, sketches were identified only around 8% of the time
Now that’s arguably better than nothing, but there are also risks to putting out a bad
sketch. This man served 12 years in prison for a crime
he didn’t commit after someone said he looked like the sketch of a rapist and then the victim
wrongly chose him from a lineup. Here’s why this is so hard. Psychologists
have long known that we process human faces holistically, rather than on the level of
individual features. Here’s an example: take a look at this photo. Now which of these is the mouth you saw? Generally people are worse at getting this right than
if the mouths are shown in the original facial context. Or try this – are the top halves of these faces the same? How about these? We’re generally
quicker to answer when the halves are misaligned than when they’re aligned. That suggests that it’s difficult for us to focus on just one part of a face. The rest of the face tends to interfere.
So our brains aren’t well suited to describe individual facial features but that’s typically
what victims and witnesses are asked to do. And that’s been the fatal flaw for the many
attempts to improve upon the hand-drawn sketch, dating back to the 1960s when police tried
using these mechanical kits of interchangeable features. Picture puzzles to put mugs in the jug. Then came computer programs that were slightly more customizable but still relied on feature-by-feature
reconstruction. In laboratory tests, these systems performed
pretty badly. But the latest generation of computer programs
seems more promising. This system was developed by psychologists at the University of Winchester
in the UK. It makes use of the fact that we’re good and recognizing faces but bad at recalling
their parts. After the victim or witness specifies the
gender, age and race, it presents randomly generated faces instead of individual features.
and all the person has to do is choose a few faces that most resemble the suspect. Using
what’s called a genetic algorithm, those faces then get bred together and a new set
of faces appears. They can also adjust holistic variables, like attractiveness.
When they tested this program in the lab, participants were able to generate these celebrity
faces from memory. And when they tried it in 5 real police departments,
it led to arrests around 40% of the time on average and up to 60% in the most recent trial.
For example, this composite helped police catch a man who raped two women in Manchester.
Someone called in after they recognized the image as a local fast food worker.
Nearly half of violent crimes go unsolved in the US. that includes around 60% of forcible
rapes. Sketches are easy to poke fun at but they’ve been one of the only tools detectives
have in the absence of other evidence. So it’s good news that in the future, they
might be slightly less of an art and more of a science.