Police forces across the country are planning to start using new mobile technology later this year that can identify suspects and instantly reveal their criminal history based on a picture of their face or iris, the colored portion of an eye.

Here's how it works: To scan a person's iris, police officers can hold the special iris-scanning camera on device, called MORIS, about 5 to 6 inches away from an individual's irises. After snapping a high resolution photo, the MORIS system analyzes 235 unique features in each iris and...