Biometrics are used in electronic identity documents in order to verify the identity of the holder. Here, biometric characteristics make it easer to determine whether the person submitting a form of identification really is the person in question. When two people look virtually identical to the naked eye, for example, a computer-aided facial comparison can tell them apart.

When this method is used (e.g. in the context of border controls), the facial image of the person at hand is first obtained from their identity document. After that, a picture is taken on site. The two images are then compared using a corresponding program. Minor changes in appearance, such as a different hairstyle, do not affect the results of this examination.

It is important, however, that the biometric characteristics stored on identity documents correspond to a minimum standard of quality. This is why various Technical Guidelines from the BSI, the ISO, and the ICAO specify uniform requirements regarding how characteristics are to be collected and how their quality is to be verified (see, for example, TR 03121-- Biometrics in Public Sector Applications). Thanks to these specifications, biometric procedures can be used across international borders.

The manner in which registration authorities collect biometric characteristics is described in greater detail under Facial Images and Fingerprints.