During DUI Arrest in California
Preliminary Alcohol Screen device (PAS device)
Usually after you have done some field sobriety tests after you got pulled over, the officer will bring out a handheld breath device that he will get you to blow into. This handheld breath machine is called a preliminary alcohol screening device (PAS device for short). Under the law it is described as a field sobriety test that the officer can use it to detect the presence of alcohol in you. Under the law, blowing into this device is supposed to be optional; the officer must tell you that you can refuse this test, unfortunately officers usually never tell you it is optional to blow into this device and they will make you blow into it. After you blow into it; they almost always will not tell you your results.
Breath machines at the police station
The results of the PAS device at the scene of your arrest are not as accurate as the breath machines at the police station that you might have blown into. Prosecutors give more weight to the breath results from the machines at the police stations. However, if the breath results from the PAS device are lower than your breath results from the machine at the police station, you can argue that your blood alcohol rose after driving and you potentially have a rising blood alcohol defense, especially if your results are near .08.