Biometric devices are typically used to protect computer devices and locations from unauthorized access. The user is required to produce the requested biometric data, either by holding the appropriate body part to a scanner or by producing a voice sample. An authorizer can require users to pass multiple biometric tests.
The downside of biometrics is that an authorizer cannot remotely allow access to the device or location for another person. The authorizer must appear in person to gain access.
There are ways that people can bypass biometric systems. People can copy fingerprints, and they can record voices. One of the most secure biometric devices is a retina scanner, because as of 2015 there is no known way to alter the pattern of a human retina.