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The Eyes in Police Work

The eyes reveal more than just the soul, particularly in police work.  Often referred to as “the mirror of the soul”, your eyes can tell if you are lying or if you’ve been drinking or taking drugs.   In addition, recent research shows your eyes can tell much about your surroundings including who or what is around you!

Most people are probably familiar with the “eye test” in DUI investigations; we have all seen it demonstrated in television shows, movies and occasionally roadside.  This test is called the nystagmus field sobriety test or, more accurately, the horizontal gaze nystagmus (HGN) test.  It is one of the most commonly used field sobriety tests.  The short description is the examiner looks for three different indicators of impairment in each eye that is represented by various specific eye movements.  If between the two eyes, four or more clues appear, the suspect likely has a blood alcohol level (BAC) of 0.08 or greater. Research shows that this test allows proper classification in approximately 88 percent of suspects. HGN may also indicate consumption of seizure medications, phencyclidine (PCP), a variety of inhalants, barbiturates, and other depressants.

Evaluating eye movements can also indicate if someone is lying.  The University of Utah researchers and educational psychologists developed software that has an effective method of tracking eye movements to detect lies. The technology works differently than polygraph tests.  Lie detection with polygraph testing measures a person’s emotional reaction to lying. But eye-tracking measures his or her cognitive reaction while reading and answering true-or-false questions on a computer.  The technology relies on the assumption that lying requires more work than telling the truth, so it looks for indications that the liar is working hard, such as dilated pupils or taking longer to read and answer the questions during the test. The test also measures reading and rereading time, as well as errors.  Experiments have demonstrated this approach is as reliable as results obtained from polygraph testing.

The most recent research is some of the most intriguing.  A UK team, along with the Department of Psychology at the University of New York, found that today’s high-resolution digital images are now so detailed they can enlarge pictures of eyes in photos and retrieve images of out-of-shot bystanders from reflections on their corneas.  Researchers found that participants were able to identify the tiny faces of people reflected in the eyes of photographed subjects, findings which could help solve crime one day.

The pupil of the eye is like a black mirror. 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.  Despite the low resolution of the blown up images, observers could accurately identify who the bystanders were. In fact, in a recent study, observers were able to identify the tiny faces 71% of the time for unfamiliar faces and 84% of the time for familiar faces.

These findings highlight the remarkable ability for human face recognition, as well as the potential of high-resolution photography.  For example, analyzing images reflected in the eyes of victims photographed in child sex abuse or hostage situations, or images of people retrieved from cameras seized as evidence in investigations, could provide vital clues about perpetrators or their associates, or link individuals to particular locations.  Hopefully this technology will be studied further and become commonplace in police work!

If you have questions about our topics today please contact us in Stillwater at 405-372-1715 .  We also invite you to visit our website at and like us on Facebook at Cockrell Eyecare Center!