Reflections in the "dark mirror" of a person's pupil could be used by police to identify criminals, piece together crime scenes or link networks of suspects.
According to the study, led by Dr Rob Jenkins at the University of York, we are able to able identify people reflected in the pupils of photographed subjects with a surprising degree of accuracy.
Jenkins and the University of Glasgow's Christine Kerr photographed eight people.
They found that test subjects were able to identify the image of someone they already knew in the enlarged pupil reflection 84% of the time.
When they did not know the person reflected, they were able to identify them against a passport photo 71% of the time.
"The pupil of the eye is like a black mirror," Jenkins said. "Eyes in the photographs could reveal where you were and who you were with."
"In the context of criminal investigations, this could be used to piece together networks of associates, or to link individuals to particular locations," Jenkins told Kurzweil Artificial Intelligence.
The reflections could be particularly useful in child abuse or kidnapping cases, where a victim is photographed by a criminal.
"Reflections in the victim's eyes could reveal the identity of the photographer," said Jenkins.
"Also, around 40 million photographs per day are uploaded to Instagram alone.
"Faces are among the most frequently photographed objects. Our study serves as a reminder to be careful what you upload."
The photographs were taken with a high-end 29 pixel camera, but the study's authors noted that as high-res cameras become more common in mobile phones, so better images may become more readily available to police.