Blood vs. Breath Tests

What a Los Angeles DUI Attorney says about Blood and Breath Tests in DUI cases:

Under the Implied Consent Laws in California, a person suspected of being impaired while driving a motor vehicle consents to a chemical test of their blood alcohol level. If they refuse the test, they will face automatic, mandatory 1 year license suspension. A person who consents to a blood alcohol level test has two choices:
-Breath
-Blood
Each of these choices has their advantages and disadvantages as we will discuss in this article.

Breath testing in DUI cases:

How Breath Testing in DUI cases works:

Breath testing in DUI cases is designed to measure the alcohol content in a person’s blood by measuring the amount of alcohol they exhale into a testing device. In theory, alcohol in the blood system will cross into the breath in the lungs of the person. This happens in the alveolar structures of the person’s lungs, where a very thin layer of tissue separates the air in the person’s lungs from their circulatory system tissue (blood vessels).
If a person has alcohol in their blood, this will cross over the alveoli membranes and into the breath testing device when the person blows into the device. It is important for the person to take a very deep breath and blow very hard, so as to get an air sample from deep within the person’s lungs. Often, impaired people cannot blow hard enough for the machine to get a sample adequate for testing.

Disadvantages to Breath testing in DUI cases:

One of the disadvantages for people chosing breath testing if they are stopped for DUI is it is often quicker for law enforcement to get the driver to a breath testing device.  Thus, there is less chance a person can “sober up” or have their blood alcohol level go down before taking test.

Another disadvantage for a driver is a breath sample cannot be preserved for future examination.  In blood test situations, the blood sample can be tested independently by a driver’s own medical lab. (This is a right every person stopped for DUI has..the right for their own medical lab to test blood tests if they were administered.)   Breath samples simply cannot be saved for future use.

Blood Testing in DUI cases:

Blood testing is more accurate than breath tests. This is because blood tests DIRECTLY measure the alcohol content of a person’s blood. Therefore, if a person is in fact above the legal limit for blood alcohol level, a blood test will show that more accurately than a breath test.

Disadvantages to Blood Tests

The biggest disadvantage for blood tests is they are highly accurate. So if a person is above the legal limit, the blood test will show this.

How a DUI attorney attacks blood testing in DUI cases:

Even though blood tests are accurate, there are ways they can be attacked. Accurate blood testing requires strict protocols that, if not followed, will effect the accuracy of the test. For example, the blood vial must have an adequate amount of preservative in it for the sample to accurately show the alcohol level when it is later tested. The sample must be refrigerated, and the police must show proper chain of custody over the sample.

These are things a DUI attorney looks at when preparing a DUI defense.

Posted in DUI Attorney.

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