When asked why they don’t fully use iris searches in their investigations, law enforcement officers often say, “Because people don’t leave their irises at crime scenes.”
While it is true that suspects don’t leave usable latent impressions of their eyes on objects or surfaces—like they commonly do with fingerprints—iris images can still be useful for identification.
The FBI’s Next Generation Identification (NGI) service provides a variety of investigative tools. The newest of them is an iris image repository that contains more than 1.7 million images. Each iris image is linked to a fingerprint record. Law enforcement agencies collect these images during criminal bookings, incarcerations, or other legal proceedings, then share them with the FBI.
An iris, the colored ring surrounding the pupil of the eye, is made up of intricate layers visible to the naked eye. These layers create distinct patterns that are unique to an individual—as distinctive as a person’s fingerprints. According to research, barring injuries or medical issues, iris patterns don’t normally change throughout a person’s life. So, technicians can use iris patterns to identify individuals using photos taken more than 20 years apart.
Currently, these images can only be taken using specialized equipment. Technicians use near-infrared cameras specially designed to capture iris images for identification purposes. However, with advancements in iris recognition algorithms, this requirement may change. The FBI continues to research potential applications and technologies for the future.