Should I Take a Breath or a Blood Test?

Posted by Jon Ibanez on November 17th, 2014

One of the most common questions I get as a DUI defense attorney is “Should I have taken a breath test or a blood test?” As with many questions in DUI law, the answer is, “It depends.”

Just to be clear, I’m talking about a breath or blood chemical test required under California’s implied consent law. This does not include the pre-arrest preliminary alcohol screening test. Although a breathalyzer, the “PAS” test is not a chemical test and is not required under California law. The chemical test, on the other hand, can either be a breath or a blood test and is required under California law once a person is lawfully arrested on suspicion of a California DUI.

The DUI blood test is much more accurate than the DUI breath test. The blood test is far less likely than a DUI breath test to produce a false reading. Another benefit of a DUI blood test is that a sample of the blood is saved for future testing by the DUI suspect’s defense attorney. The defense attorney can have the sample tested by its own blood analyst to contradict the results of the prosecutor’s analyst. This is called a “blood split” and it is commonly used in DUI defense.

Having said that, the blood test can still be subject to scrutiny. See my previous post: http://ltduiblog.wpengine.com/2014/09/15/the-dirty-skin-defense/

In other words, the blood test may be good for someone who is under the legal limit because it is more accurate. The blood test might be bad for someone who is over the legal limit because it is more difficult to refute the accuracy.

The DUI breath test, on the other hand, is far less accurate than the DUI blood test. Breath tests can provide false readings for a number of reasons. See Lawrence Taylor’s post: http://ltduiblog.wpengine.com/2014/09/09/are-breathalyzers-accurate/

While California defense attorneys cannot challenge the unreliability of breathalyzers on a general basis, they can provide evidence that the particular breathalyzer used on the DUI suspect was inaccurate.

The breath test may be good for someone who is over the legal limit because it is easier for a California DUI attorney to refute the results. However, many people who are actually under the legal limit may test over because of the breath test’s inaccuracies.

If you are fairly confident that your blood alcohol content will below the legal limit of 0.08 percent, you’re probably better off opting for the blood test because it will accurately show that you were, in fact, under the legal limit. However, if you think there is a chance that you could be above the legal limit, you might be better off opting for a breath test so that your attorney can challenge the results if you test above the legal limit.

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