Many DUI cases in California involve a reading with a Blood Alcohol Concentration (BAC) over 0.08 percent on the Intoxilyzer 5000 breathaylzer. The machine is manufactured by a company called CMI, Inc.

The median blood alcohol concentration (BAC) of a convicted DUI offender, as reported by law enforcement on Administrative Per Se (APS) forms, was 0.15% in 2011. That median BAC of 0.15% was the same as in the last 7 years, but almost double the California illegal per se BAC limit of 0.08%. The average reported non-zero BAC level for all convicted DUI offenders arrested in 2011, using APS reporting forms as the data source, was 0.16%.

Breath testing must be in compliance with Title 17 of the California Code of Regulations. Title 17 establishes the rules for how the State of California will maintain the breath test instruments and collect the breath test samples from those arrested for DUI. A failure to comply with Title 17 regulations can result in an inaccurate or unreliable BAC level.