The choice of a biometric trait or traits to use in a security system depends on the application; the strengths and weaknesses of each of the four most common biometric identifiers are summarized in the table below. For example, compared with fingerprint recognition, iris recognition allows access to the wrong people less often but currently requires larger and costlier sensors and thus cannot be as easily incorporated into a laptop or other consumer device. Experts concur that in an ideal biometric authentication system, neither the “false accept” rate nor the  “false reject” rate should exceed 0.1 percent. In tests conducted by the National Institute of Standards and Technology, however, none of the systems satisfied these error rate requirements.

  Fingerprint Face Iris Voice
Distinctiveness High Low High Low
Permanence High Medium High Low
How well trait can be sensed Medium High Medium Medium
Speed and cost efficiency of system High Low High Low
Willingness of people to have trait used Medium High Low High
Difficulty of spoofing the trait High Low High Low
False reject rate* 0.4 % 1.0 - 2.5 % 1.1 - 1.4 % 5 - 10 %
False accept rate* 0.1 % 0.1 % 0.1 % 2 - 5 %
*Error rates depend on testing environment, sensors used and composition of users in the population.