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Blood Test for a DUI – What You Need to Know

Blood test results are more reliable than results from PAS devices. The red and blue lights are flashing. Your heart is beating rapidly. You think back on the past few hours of fun you’ve had, and you try to remember how many drinks were put on your tab since you’ve been out. Before you know it, a police officer is knocking at your window, asking your license and vehicle registration.

If you’ve been pulled over because you’re suspected of driving under the influence, you may be asked to perform roadside field sobriety tests (FST) to help the officer on duty determine your level of intoxication. Besides FSTs and preliminary alcohol screening (PAS) devices (commonly referred to as breathalyzers), your blood can also be drawn to test for levels of alcohol in DUI situations.

Related: How Do Preliminary Alcohol Screening (PAS) Devices Work?

Here are a few things you should know about blood tests for a DUI:


Blood test results are more reliable than results from PAS devices. PAS devices are known to be very inaccurate due to many reasons, including out-of-date calibration and simple mishandling of the devices. Blood tests, on the other hand, are generally handled by certified laboratories that are required to adhere to strict guidelines that are meant to ensure the quality of the sample.

Blood Alcohol Content (BAC) is measured in terms of grams of alcohol per 100 milliliters of blood. Simply put, BAC is a measurement of the alcohol in your bloodstream, not the amount of alcohol you exhale from your lungs.

While breathalyzers (PAS Devices) can provide officers with probable cause to arrest, they are generally not equipped to measure your blood’s alcohol content with accuracy.


Many people think they must say yes to submitting to the PAS (breath) test if they’re pulled over for a DUI. This isn’t the case. In fact, it’s often wise to refuse the PAS – breath test in lieu of a blood test if you’ve been arrested. While PAS tests will typically be administered on the scene, blood tests must be administered in a sterile environment by trained professionals. This process usually takes place hours after the initial arrest.


Lab testing errors can throw off the results of your blood alcohol test. In short, humans perform the lab tests. As such, human error could absolutely happen. If the sample wasn’t properly preserved, the blood can ferment, which could cause inaccurate high results. Some of the procedures in L.A. crime labs are out of date.

Your lawyer should be able to find these issues if they exist and fight them in court.

Independent Testing.

You do have the option of obtaining a sample of your blood and having it tested by an independent lab. Be advised, the results could work in your favor, or against you, so it’s best to speak to an experienced DUI attorney to determine the best course of action for your specific case.

Other Considerations.

Blood tests can be very unforgiving. It’s important to remember that alcohol isn’t the only element considered when people are considered intoxicated or driving under an influence.

If other substances show up in your bloodstream — such as illegal drugs or substances that prevent you from being in full control — you could face additional misdemeanor charges for being under the influence of a controlled substance.

Being pulled over by the police can be a scary situation for anybody. It’s important to be mindful of the law while also knowing your rights. If you or a loved one has been charged with a DUI, consider contacting an attorney who specializes in DUI law. An experienced DUI attorney can help you get the best results for your individual circumstances.

If you have been arrested for DUI in the Los Angeles area, contact us today by filling out the form or calling (310) 820-1315.

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