Pupil Reflections In Photos Of Victims' Eyes Could Help Police Catch Perpetrators

By Josh Lieberman on December 28, 2013 5:10 PM EST

Reflections of bystanders can often be extracted from zoomed-in images of pupils, a technique which can help in police investigations. Photo: Flickr user artwork_rebel

Reflections of bystanders can often be extracted from zoomed-in images of pupils, a technique which can help in police investigations. Photo: Flickr user artwork_rebel

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Police may be able to identify perpetrators of crimes by zooming in on victims' eyes, according to new research published in PLoS One. Researchers from the University of York in England and the University of Glasgow in Scotland found that "surprisingly rich" photographic information could be obtained from the pupils of photographic subjects. The technique could be particularly useful in crimes in which the victim is often photographed, such as hostage taking or child abuse, as the face of the photographer/perpetrator may be clearly visible in the pupil of the victim.

"Cameras are routinely seized as evidence during criminal investigations," the researchers write. "Images of people retrieved from these cameras may be used to piece together networks of associates, or to link individuals to particular locations. In particular, it may be desirable to identify the photographer, or other individuals who were present at the scene but were not directly captured in the photograph."

In the study, psychologists Rob Jenkins and Chistie Kerr took passport-style photos of people with bystanders around them and zoomed in on the photo subjects' pupils. Jenkins and Kerr showed study participants the "eye-reflected" images of the bystanders, and although the zoomed-in images weren't of great quality, study participants were able to identify bystanders they didn't know 71 percent of the time in a face-matching test. When the participants were shown eye-reflected images of bystanders they did know, they were able to identify them 84 percent of the time.

If you want to play along at home, take a look at the image below. Although it's highly pixelated and seemingly offers little photographic information, you can almost definitely identify the subject in the picture.

"The pupil of the eye is like a black mirror," said Jenkins. "To enhance the image, you have to zoom in and adjust the contrast. A face image that is recovered from a reflection in the subject's eye is about 30,000 times smaller than the subject's face. Our findings thus highlight the remarkable robustness of human face recognition, as well as the untapped potential of high-resolution photography."

Even though the researchers zoomed in on high-resolution photographs, Jenkins noted that even low-resolution photos of victims could still help ID perpetrators, especially if the person viewing the photo knows the possible perpetrator. As Jenkins told KurzeilAI, "Obtaining optimal viewers--those who are familiar with the faces concerned--may be more important than obtaining optimal images." Jenkins also noted that the "pixel count per dollar" for digital cameras is doubling every year, so in just a few years mobile phones may have resolutions equal to the 39-mexapixel camera Jenkins' team used in the study.

And here's a fun fact: the world "pupil" comes from the Latin word "pupilla," meaning "little doll," because of the small reflection a person sees of himself when looking into another's eyes.

READ MORE:

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