The only circumstances under which you should submit to a preliminary breathalyzer test in the field in California, is if you’re under 21 and requested to do so by an officer, on DUI probation and are required to submit as part of your terms and conditions, or if you did not consume any alcohol within 24 hours.
The preliminary breathalyzer is generally a voluntary test and the results are usually not reliable. BAC results, with these devices, commonly read higher than someone’s actual BAC level. Scientific studies have shown that breathalyzers provide false high readings during the absorptive phase, which can last for an extended period of time after your last drink. Also most of these devices do not have certain mechanisms, such as a “slope detector,” which factors in contaminants like mouth alcohol and provides a safeguard for the reliability in the results. Thus, the results do not reflect your BAC level and are likely to register higher than what your BAC level actually is.
So when confronted by an officer conducting a DUI investigation in California that asks you to submit to a breathalyzer in the field, before you are arrested, you must politely inform him that you know your constitutional rights to refuse this test. Tell him you’ve been advised that the breathalyzers may falsely misrepresent your actual BAC level and that you don’t want to submit to anything that could improperly incriminate you. You should have the same response ready when the officer requests field sobriety tests.
A common public misconception is that this preliminary breathalyzer test will show you’re innocent (below 0.08%), and the officer will then let you go. But, as explained above, you may be below 0.08% and still register well above if you’re still absorbing alcohol. Also, even if you’re below 0.08%, you can still be arrested and charged with a DUI under California Vehicle Code § 23152(a).
By refusing to submit to the breathalyzer in the field, and refusing the field sobriety tests, you can limit the amount of evidence the officer and prosecutor can use against you. This would allow a qualified DUI attorney to potentially challenge the constitutionality of the arrest, with a suppression motion. It would also help in negotiating a plea, because it would limit the prosecutor’s evidence in your case. Finally, it would make it more difficult for a prosecutor to prove you were DUI, beyond a reasonable doubt, in trial.
For more information, visit: What to do when arrested for a DUI