Most Los Angeles County Police Agencies and the California Highway Patrol are employing the use of field breathalyzers known as Preliminary Alcohol Screening devices to determine a person's alcohol level at the side of the road. Known as a PAS device, this is a small hand-held box that is placed in front of the driver's face with the instruction to blow hard. These field breath machines are notoriously difficult to calibrate and can trigger on any "methyl" based chemical on the breath. A person who was stopped shortly after their last drink of alcohol may still have active particulates of alcohol in their mouth and be blowing straight alcohol in to the machine. This may be an accurate representation of what is present in their throat and mouth but may wildly overstate the actual amount of alcohol that has been absorbed into the body. Also, because these breath machines are not designed to be specific to Ethyl Alcohol (ETOH), they may trigger on mouth washes, mints, or other chemicals that occur naturally in the body. There are studies on file which prove that a person with diabetes will have an elevated level of acetone on their breath which can register as alcohol on the PAS device.
Typically, these breath devices do not meet the "Frye Standards for Scientific Evidence" and are often thought of as being inaccurate. Despite this, police officers place blind trust in the accuracy of their machines. Even if you were to perform perfectly on the Field Sobriety Tests, you can be certain you will be arrested for DUI if a hand-held breath device registers .08% or greater. The breath machines are blind to the fact that they may "misread" a foreign chemical on the breath and; police officers are taught to trust these devices implicitly.
California Vehicle Code (CVC) section 23612(i) specifically instructs police officers to tell drivers of their right to decline a breath test at the side of the road. This section reads,
"If the officer decides to use a Preliminary Alcohol Screening test, he shall advise the driver that upon arrest, the obligation to submit to a blood, breath, or urine test is not satisfied by the person submitting to a Preliminary Alcohol Screening test. The Officer shall advise the person of that fact and of the person's right to refuse to take the preliminary alcohol screening test."
This language in the California Vehicle Code is unambiguous and tells the officer that they shall give this admonishment however, dozens of times a year we find evidence that officers are not advising citizens of their right to decline these wildly inaccurate tests.
For the results of these field tests to be admissible in court or at the DMV; the prosecutors or the DMV Hearing Officer must establish a "foundation" upon which to argue the accuracy of the tests. Your Los Angeles County DUI attorney is an expert at attacking these devices and keeping their readings out of your case.