In 1892 Galton looked at the pattern of whorls, arches and loops that make up fingerprints, and estimated that the chance of two prints matching at random was about one in 64 billion.

ECONOMIST: Fingering fingerprints

With the exception of the Apple logo, the back and sides have a matte finish that make them impervious to fingerprints.

ENGADGET: We've got iPhones, what do you want to know?

If they can pick up fibres or fingerprints from a crime scene, they can trace it back to the year, make, model of the car that the fibre came from and the thumb that left the fingerprint.

BBC