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Does An Alcohol Swab Affect The Result Of A DUI Blood Test?

A swab used for DUI purposes is supposed to be non-alcoholic. But most of them have a small percentage of alcohol. That’s why the World Health Organization (WHO), are the ones who recommend regulations. There are also regulations under Title 17, which regulates breath and blood testing in California. The WHO recommends that once the swab has been put on the arm, that the phlebotomist wait 30 seconds for any substance that’s in the swab or in the material to evaporate. The site has to be cleaned and the air helps it evaporate. From there, it’s okay to do the puncture. So, can an alcohol swab affect the results of a blood test? Yes, it can.

If they used the wrong type of swab with alcohol in it and don’t let it air out long enough, that can have an effect. Sometimes, when they are letting it air out, they may touch it again with their glove, and that too can affect the results. That’s something we may be able to catch on video. They could have been picking up papers, moving stuff around, touching a computer, a desk, or their face. Anything can contaminate the area where the swab cleaned the puncture area. The tourniquet strap, which is up the arm, could also fall onto the swab site and contaminate it. There are many different things that can happen, which is why I always ask for the video of the blood draw in my blood cases. Every once in a while, we get a phlebotomist making mistakes. That’s something that can help us win a case and get a better result.

If Given A Choice, Should I Take A Breath Test Or A Blood Test?

If given a choice between a breath test or blood test, choosing the one you should take will depend on the circumstance. A blood test is usually more accurate. A breath test has a ratio of conversion of 2100 to 1, and there is a mathematical formula. A lot more has to be done for a breath test, and it’s a little less accurate. There is a larger margin of error on breath testing when you talk to most experts in the field. However, breath testing has gotten much better over time. Most of the machines that are used in the San Francisco Bay Area, whether it is Marin County, Sonoma, Napa, Alameda, Contra Costa, San Francisco, Santa Clara, or San Mateo, most of those counties now use Draeger machines.

Draeger machines test for fuel cell and infrared. They use those two different types of technology. So, they test in two different ways with breath testing. Those machines are usually calibrated properly, so it’s rare when they get taken out of service or are having problems. That’s something that we always check into and investigate in all of our cases. But, they are more reliable than they used to be. The old Intoxilyzer 5000 was a 40- or 50-pound metal machine, like a big typewriter. It was something that had a lot more things that could go wrong. It was not as efficient. It only tested through the infrared technology, and not fuel cells. And so, breath testing is something that has gotten a lot better.

Now, when deciding between breath test or blood test, you also have to ask: What is in your system? If it’s just alcohol, then either a blood test or breath test will do. But, if you have alcohol and drugs or alcohol and prescription drugs in your system, you won’t want to do a blood test. The reason is because that’s just going to give the prosecutor and the district attorney in the San Francisco Bay Area or county you are in more information. You’ll be giving them more tools in their box; more things to go after you with. If you are at, over the limit, or just under with drugs in your system as well, they can say that the combined substances make you that much more impaired, which according to science and common sense, in a lot of cases, it does. Therefore, you don’t want to take a blood test if you have drugs in your system.

Blood testing has less of a margin of error. It’s a direct test, but there are things that can go wrong with blood testing too. Whether it has to do with the method used to test or the actual testing of the blood once it’s been sent to the lab, things like contamination can happen. There are a lot of things that we can go after with blood testing, and I wouldn’t say I prefer to fight a blood case, but I’d have a lot more things to talk about, to look at, and to examine when blood testing is involved. As mentioned, there is less margin of error, so if it’s right on the borderline, that’s where breath testing might be the better option. Unfortunately, we don’t know. If you do the preliminary alcohol screening test as the last field test before they decide to arrest you, it’s best if you can take your time if you are able to, especially if you had your drinks a while ago. The hope is that more alcohol burns off before they do the next test, regardless of whether it is breath or blood.

A lot of times, they are ready to do the evidential breath test right there on the spot or when you get to the station. By contrast, a blood test requires a phlebotomist, an EMT, or a nurse to administer it. Unfortunately, most people who do get into these situations don’t have a clear mind at the time. They most likely haven’t watched videos on blood and breath testing, and are not aware of the choices and options they have until after they’ve been arrested and released. Most people start searching for information after the fact to try and find out as much as they can about how DUIs work and how to defend against them. Reading websites, watching videos, and gather information like this are tools that most people don’t have when these situations occur.

I hope people are learning a lot now. Unfortunately, it is usually a little too late. But, a lot of this information can help with trying to find an attorney, ask the right questions, and let other people in the future know just in case they get into similar circumstances. I hope they don’t. But as we know, we are all humans. We make mistakes, and these things unfortunately are going to continue to happen. If they do, we are here to help.

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For more information on Impact Of Alcohol Swab On A Blood Test In CA, a free initial consultation is your next best step. Get the information and legal answers you are seeking by calling (415) 523-7878 today.

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Aaron Bortel
With 30 years of specialized experience in DUI defense, Attorney Aaron Bortel is a dedicated advocate for those facing DUI charges in the Bay Area. Committed to helping clients avoid jail, save their driver’s licenses and jobs, and prevent permanent criminal records, he combines deep legal expertise with genuine care for his client's welfare. Trust in a lawyer who not only defends but truly supports you through challenging times.

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