RTFA: http://www.duiblog.com/2007/09/04/secret-breathalyzer-software-finally-revealed/

10. Error Detection Logic: The software design detects measurement errors, but ignores these errors unless they occur a consecutive total number of times. For example, in the airflow measuring logic, if a flow measurement is above the prescribed maximum value, it is called an error, but this error must occur 32 consecutive times for the error to be handled and displayed. This means that the error could occur 31 times, then appear within range once, then appear 31 times, etc., and never be reported…
Based upon a .08% reading from this machine, American citizens are accused of drunk driving and, in court, presumed by law to be guilty.

Analysis of breathalyzer source code reveals the system is unable to produce reliable results! As the link points out, based on a breathalyzer reading, people are determined to be guilty or not guilty of a crime. That is to say, innocent people are turned into criminals – convicted of criminal behavior – when in fact no crime has even taken place.