However, Cook County (Illinois) is experimenting with a biometric identification device, the retinal scanner, that could end such impersonations. The device identifies persons by their unique retinal patterns on the back of the eye. The Eyedent System allows positive identification of an individual on the spot by matching up a unique and unchanging physiological characteristic. A retinal screening of each inmate takes place during registration; the machine calculates the agreement between several different photographs to ensure proper identification. The inmate's retinal scans of both eyes and text occupy about 1,200 bytes of computer disk space, while each fingerprint takes up 10,000 bytes in comparison. The Eyedent System identifies suspects living as fugitives or behind aliases, establishes criminal histories, and prevents identity switching. 1 figure