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Breath vs. Blood Test for DUI Stop

You are stopped by police and they suspect that you have been drinking. After the officer asks you a few questions, he then directs you to step out of your car. He plans to use some field sobriety tests to determine your level of impairment. Results from field sobriety tests are rarely conclusive. You can refuse to submit to field sobriety tests, but the police will probably assume you are impaired and will then choose to conduct one of two chemical tests: the breath or blood test. In many states, you have some degree of choice as to how your blood alcohol content will be calculated. Some states don’t leave the choice up to the driver; they let the officer decide which test he will administer. For example, in Texas, if the officer chooses to give you a breath test and you decline and ask that he test your blood instead, you will be charged with a refusal because you did not submit to the breath test. Other states give the driver the option; which leaves an important question: Should you take the blood or breath test?

Accuracy of DUI Chemical Testing

In most instances, the blood test will be more accurate. Breath machines require regular maintenance and the police must calibrate the device properly. The accepted error range of a breath machine is .02%. In fact, there was a study conducted in Florida recently that showed close to 40% of all results from breath test machines (Intoxilyzer) were abnormally high. These types of reports spread doubt about the accuracy of these portable devices.

Difficulties with the blood tests for DUI

There are procedures that police must follow when administering a blood alcohol test, not to mention that they must keep track of the chain of custody to ensure the sample tested is really yours. If the lab waits too long to test the sample, it could ferment and produce more alcohol within the sample. Or, if the blood coagulates, it would thicken and greater concentrate the alcohol content.

Difficulties with breath tests for DUI

As mentioned previously, the machines provide several ways to return inaccurate readings. Most breathing test procedures require the police to wait 15 minutes before beginning the test. The driver must be continuously observed during this time. The reason for the delay is to remove any mouth alcohol that may be present that could give an inaccurately high reading. Many different substances, other than alcohol, can be read as alcohol by the machine. For example, diabetics with ketones on their breath, exposure to paint fumes, gas and/or glue can all give a false reading. Also, people who have dentures, acid reflux, or have recently vomited can also ‘fool’ the machine into giving a high reading.

So…should I take a blood or breath test?

The general consensus among DUI attorneys is that if you are confident that you BAC is below the legal limit, then you should ask to take the blood test. If you think you are above .08%, then choose the breath test. It has been proven to be unreliable, less accurate and gives a skillful DUI attorney several areas of weakness to argue before a jury