Miami DUI Defense Attorney Izquierdo Law FirmYou were pulled over, given a roadside sobriety test, and charged with driving under the influence. Now you’re wondering just how alcohol breath tests work and whether they are accurate or not. You are right to question the accuracy of the test, but without an experienced DUI attorney on your side, you will not get far in launching a defense based on an inaccurate breath test. Learn more about these tests and how the Izquierdo Law Firm may be able to defend you in court.

How an Alcohol Breath Test Works

So, how can the amount of alcohol in your blood be measured by collecting a sample of your breath? The answer is, it can’t. Even though the test result is stated in terms of blood alcohol content (BAC), what is actually being measured is the amount of alcohol vapor in your breath.

When you have an alcoholic drink, some of the alcohol will pass into your bloodstream and travel throughout your body. In your brain, the alcohol in your blood attaches to nerve receptors and causes sleepiness and behavioral changes—what we know as drunkenness. As blood passes through the lungs, alcohol vapor escapes the body when you exhale. A breathalyzer test captures your breath and measures the amount of alcohol vapor it contains.

In developing a breath test to measure blood alcohol content, scientists discovered a relationship between the amount of alcohol vapor in the breath and the amount of alcohol in the blood. Known as a partition ratio, this is a calculation that estimates the amount of alcohol in the blood by multiplying the alcohol vapor in the breath by a standard number.

What Can Go Wrong With a Field Breath Test

Even though breathalyzer tests are widely used by police and accepted as proof of impaired driving by courts, there is a lot that can go wrong with them. You cannot refuse a breath test in Florida, but that doesn’t mean you don’t have rights regarding when and how it is administered. An experienced DUI defense attorney will examine the circumstances of your breathalyzer test and may be able to build a defense based on one of the following:

Faulty Device 

Breath test machines must be stored securely, inspected regularly, and maintained adequately. If the device used to test you is found to be faulty, or there is evidence that it was not handled properly, your results should be excluded.

Lack of Calibration 

Breathalyzer machines must be calibrated regularly. Calibration is the process of testing and adjusting the device for accuracy by comparing the results to a known value. Each device should be properly calibrated at least once a month.

Tainted Breath Sample 

If the breath test device was not properly cleaned or fitted with a new mouthpiece after its last use, your test could be affected by the previous user. Your breath sample could also be tainted by something in your mouth, such as mouthwash, vomit, or vapor from a burp. 

Improper Test Administration 

The officer giving your breath test should have been trained in the proper procedures for administering the test and should follow the required steps to the letter. If there is any departure from the correct procedure, your results could be tainted and should not be used.

In addition to problems with the testing device and the administration of the test, your defense attorney may build a case based on the legality of the traffic stop and whether you exhibited any signs of drunkenness or impaired driving before your arrest.

Do You Need A Miami DUI Defense Lawyer?

If you find yourself charged with DUI in Miami you need to speak with an experienced DUI attorney as soon as possible. Please contact me online or call my Coral Gables office directly at 305.707.7345. You should also download my free book "A Six Pack Of Questions That Can Cause A Hangover After A DUI Arrest". This free download provides valuable information and answers to questions about DUI charges that can give you the best chance at winning your case.


Daniel Izquierdo
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Coral Gables defense lawyer helping clients accused of Federal Crimes, DUI, Domestic Violence & Sex Crimes.