Eye reflections in photos could catch child abusers
Reflections caught in the eyes of child sex abuse victims in photographs could help police to identify and catch the perpetrators, thanks to new research from two UK universities.
Psychologists at the University of York and the University of Glasgow were able to extract images of people standing behind the photographer from reflections in the eyes of subjects. They then discovered that they were identifiable by third parties, despite their low resolution and poor quality.
The iris typically occupies only 0.5 per cent of the area of a person’s face, meaning that the amount of reflected data that can be extracted to form an image is extremely small. Advances in camera technology have increased the number of pixels captured over the years but researchers found that the quality of images of reflected faces remains around 30,000 times lower than a face directly visible in the same photograph.
In the experiments, published in the journal PLOS One this month, people were photographed with a 39 megapixel camera and reflections in the eyes of the subject were cropped and magnified. The quality of camera used in the experiment is already available commercially; Nokia’s Lumia 1020 smartphone is already on the market with a more powerful 41 megapixel sensor.
Previous research has shown that people can identify familiar faces from extremely low resolution images, down to just seven by ten pixels. Current technology means that it is possible to gather images of at least this quality. But the scientists were surprised to discover that even unfamiliar faces are distinguishable at this quality.
During the experiments it was shown that those familiar with a person could identify them from reflected images 84 per cent of the time. Crucially for law enforcement use, even those unfamiliar with the person were able to correctly state whether or not they were the same individual as that shown in a second, a high-quality image with an accuracy of 71 per cent in a second experiment.
The researchers suggest that the technology could prove invaluable for police in linking multiple suspects with each other in complex criminal cases or in identifying child sex abusers who personally photographed their victims. It could also be used to gather more information in hostage scenarios where videos or images are released.
Researchers said that if images were available from both eyes in an image, that a 3D image could be constructed from the subject’s viewpoint.