Breath testing is a common tool in DUIs to determine a person’s blood alcohol content or BAC. There are two different kinds of breath testing, and they’re done at different stages of a DUI investigation. This guide will go over what those kinds of breath testing are when they’re used during the DUI investigation, a person’s legal obligations concerning them, and other things to think about if you’re ever pulled over and the officer conducts a DUI investigation.

The officer does not need to pull you over on suspicion that you were driving under the influence to arrest you for a DUI. If the officer pulls you over for another traffic-related violation and becomes suspicious that you may be intoxicated, the officer can start the DUI investigation at that time. However, the officer needs more than just a suspicion that you were under the influence to make a DUI arrest. The officer must either observe “objective signs of intoxication,” or certain actions, behavior, or conduct that the driver exhibits that give the officer reason to believe that you are under the influence of a drug or alcohol, or measure your BAC.

At the end of conducting Field Sobriety Tests, or FSTs, the officer may request that you take a Preliminary Alcohol Screen test, more commonly known as the PAS. It is also colloquially known as a breathalyzer. In general, you can and should refuse to take the PAS breathalyzer. The point of the test is to give the officer probable cause to arrest you for driving under the influence. But there are certain circumstances where you will not be able to refuse. First, if you have been convicted of a prior DUI and a condition of your probation is that you must submit to PAS, then refusing the PAS will be a violation of your probation, which can lead to further penalties associated with your probation. Second, if you are under 21, the PAS is mandatory.

Before the test, the officer is required to give you a PAS admonition. In the admonition, the officer should say that you may refuse to take this test. If you choose to take the test, then the officer will calibrate the handheld PAS machine, and ask you to blow into it. The machine needs a strong breath in order to work, and if your blow is not strong enough, the officer may count it as a refusal. The officer should get the test results immediately or soon after the test is conducted, and will note it in the police report.

Then depending on the results of the PAS and the officer’s observations, the officer may arrest you for driving under the influence. If arrested, then the second kind of breath testing may come into play. The officer will transport you to the station, where he must give you a choice between taking a chemical breath test or a blood test. You must take either the chemical test or the blood test, and the officer must also tell you what the consequences are for refusing to take both tests. If it’s your first DUI, then the penalties for refusing to take the chemical test include an additional 48 hours in jail, a 1-year suspension of your driver’s license, and an extra 6 months on your DUI class. If you have had prior DUIs, then the penalties will include more jail time and a longer license suspension depending on how many prior DUIs you’ve had. A DUI counts as a prior if you were convicted of the DUI, and the arrest date for that DUI is less than 10 years old.

The chemical test is more accurate than the handheld PAS, and can more accurately determine your BAC. If you choose the chemical test, then the officer must observe you for fifteen uninterrupted minutes to ensure that you don’t belch, burp, vomit, pee, or do anything else that would remove alcohol from your system. Then the officer will ask you to blow into a large breathalyzer machine. The machine should return the BAC results immediately or soon after the test is conducted, and the officer will note it in the police report.

Weaknesses of the PAS and Chemical Tests

These tests, despite their technology, have their weaknesses. The first and most glaring flaw is that they do not capture what the prosecution needs to capture to convict you of a DUI. In order to be convicted of a DUI, you need to have a BAC of 0.08% or higher while driving a car. While both the PAS and chemical tests measure BAC, they cannot measure your BAC at the time of driving, because the officer is not in your car with you, having you blow into the breathalyzer to get the result while you’re driving. Therefore, just because your PAS or chemical test result comes back over 0.08% BAC, doesn’t mean you’re guaranteed a conviction for a misdemeanor DUI. Instead, there are several defenses that may be available to you in your case.

Second, despite their alleged accuracy, these devices can still make errors. These device results do not directly capture your blood alcohol content. The devices measure the amount of alcohol in your breath and use a series of calculations to estimate your blood alcohol content. If the machines are not functioning properly, then the results they produce can be incorrect and can be used for a favorable outcome in your case.

The first type of error that can be used as a defense against a DUI is the margin of error in the BAC results. A typical PAS or chemical test device’s margin of error is around 0.02%. This means that if the machine gives a result of 0.08%, your actual blood alcohol content could be anywhere between 0.06% to 0.10%. Because there is a chance that your BAC could have been below 0.08%, your attorney can use that to get a favorable result at trial or get a better deal.

The second type of error is calibration error. These devices have to be calibrated by law on a specific schedule. The PAS and chemical test machines have to be calibrated after 10 days or 150 uses, whichever comes first. The law enforcement agency also has to keep detailed records of all testing and calibrations. If the machine is not calibrated after 10 days or 150 uses, then it’s likely the result it produced for you was incorrect. Your attorney will be able to argue that the incorrect result cannot be used to convict you for driving under the influence.

Contact an Oakland DUI Attorney Now

The attorneys at Lamano Law Office have over 30 years of experience handling DUI matters and will be able to identify defenses for your case, as well as find the weaknesses of the PAS and chemical test devices used on you to get you a more favorable result at trial or a better deal. If you have more questions, please contact us at or call us today to get an evaluation of your case.