It is certainly the case, I think as the FBI has pointed out, that when preliminary tests are done, secondary and I suppose tertiary tests are made because of the need for accuracy and to be sure about what the substances might be.

WHITEHOUSE: Press Briefing

In the future, software for voice and facial recognition will surpass all the current biometric tests in terms of accuracy and ease of use.

WSJ: Eric Schmidt and Jared Cohen: The Dark Side of the Digital Revolution