Breath Alcohol Testing

Marin County driving under the influence (DUI) prosecutions most often rely on a breath alcohol test administered on the Alcotest 7110 MKIII-C breath alcohol testing device manufactured by Drager Industries. The machine utilizes dual technology, incorporating both infrared and fuel cell technology to determine the blood alcohol level of individuals suspected of driving under the influence of alcohol.

The way the Alcotest 7110 operates is by shining infrared energy (a light bulb) through an 80 cubic centimeter sample chamber (pipe) towards a detector positioned at the other end of the sample chamber. Molecules resembling alcohol absorb this infrared energy (light) which allows less energy to reach the detector. The difference between the amount of infrared energy expected to reach the detector and the amount which actually reaches the detector during a breath alcohol test is how the blood alcohol level is calculated.

Although all law enforcement agencies making DUI arrests in Marin County rely on the Alcotest 7110, the device is not infallible nor completely accurate. In fact, in November of 2005, a Florida court ruling disallowed use of the Alcotest 7110 because the manufacturer, refused to provide information and details about how the device computes Breath Alcohol Content. California law requires evidential breath tests to be conducted in compliance with the California Code of Regulations. Title 17 is the governing section of the California Code of Regulations applicable to alcohol breath tests.

While the Alcotest 7110 may be the "Gold Standard" for law enforcement making DUI arrests in Marin County, it is by no means absolute or incontrovertible evidence that a person was at a particular blood alcohol level at the time of driving. Many factors, including an individual's physiology, can undercut the accuracy of the Drager Alcotest 7110 MKIII-C.